Reactions of polyhalogenated aromatic compounds and related ethers with metal/ammonia solutions

This work contains the results of a series of reduction studies on polyhalogenated aromatic compounds and related ethers using alkali metals in liquid ammonia. In general, polychlorobenzenes were reduced to t he parent aromatic hydrocarbon or to 1 ,4-cyc1ohexadiene, and dipheny1ethers were cleaved to the aroma tic hydrocarbon and a phenol. Chlorinated dipheny1ethers were r eductive1y dechlorinated in the process. For example, 4-chlorodipheny1- ether gave benzene and phenol. Pentach1orobenzene and certain tetrachlorobenzenes disproportionated to a fair degree during the reduction process if no added proton source was present. The disproportionation was attributed to a build-up of amide ion. Addition of ethanol completely suppressed the formation of any disproportionation products. In the reductions of certain dipheny1ethers , the reduction of one or both of the dipheny1ether rings occurred, along with the normal cleavage. This was more prevalent when lithium was the metal used . As a Sidelight, certain chloropheno1s were readily dechlorinated. In light of these results, the reductive detoxification of the chlorinated dibenzo-1,4-dioxins seems possible with alkali metals in l iquid ammonia.

Reactions of some non-enolisable chloroketones with amide ion and a new synthesis of acridones /|nGuo-shyoung John Chen. -- 260 St. Catharines, Ont. : [s. n.],

This research was directed mainly towards the investigation of the reacti.ons of· substituted chlorobenziophenones under strongly basi,c conditions. The work 'can be divided into two main sections. The Introduction deals mainly with historical studies on aryne chemistry and the Haller-Bauer reaction. Secti.on I i.s concerned with syntheses of 2-benzamido-2'chlorobenzophenone and 2-benzamido~3'-chlorobenzophenone,and with thei,r respective reactions wi.th potassium amide in ammonia. o-Chlorophenylacetic acid was converted to the acid chloride and then by Friedel-Craftsreaction with benzene to w-(o-chlorophenyl)acetophenone. Reaction wi.th phenylhydrazine and Fischer cyclization gave 3- (0chlorophenyl)- 2-phenylindole, which was ozonized to 2-benzamido-2'chlorobenzophenone. The isomeric 3' -chlor,..o ke: tone was similarly synthesised from m-chlorophenylacetic acid. Both the 2'- and 3' -ch.loroketones gave N-benzoylacridone on treatment with potassium amide in ammonia; an aryne mechanism is involved for the 3'-chloroketone but aryne and nucleophilic substitution mechanisms are possible for the 2'-chloroketone. Hydrolysis of the 2'- and 3'-chloroketones gave 2-amino-2'chlorobenzophenone and 2-amino-3'-chlorobenzophenone respectively. A second new acridone synthesis is given in the Appendix involving reactions of these two ketones with potassium t-butoxide in t-butylbenzene. i Section 2 deals with the investigation of the reaction of some tricyclic ch1orobenzophenones with potassium amide in liquid ammonia. These were 1-ch1orof1uorenone; which was pr~pared in several steps from f1uoranthene, and 1- and 2-ch1oroanthraquinones. 1-Ch1orof1uorenone gave 1-aminof1uorenone ; 1-ch1oroanthraquinone gave 1- and 2-aminoanthraquinones; 2-ch1oroanthraquinone was largely recovered from the attempted reaction.

The preparation and reactions of some 1, 2-dipolar species /|nI. D. Brindle. -- 260 St. Catharines, Ont. : [s. n.],

This research was directed mainly towards the investigation of the reactions of allylic amineimides. The work can be divided into two main sections. Section 1 of the thesis deals mainly with thermolysis studies of amineimides. Sections 1a and 1b represent a comprehensive survey of amineimide literature up to 1971. N-A1ly1-N,N-dirnethylarnine-benzirnide was prepared and rearranged at 1400 to l-allyl-1-benzoyl-2,2-dimethylhydrazine. A tentative mechanism involving an initial migration to the carbonyl oxygen was disproved by incorporating the amineimide system into a five-membered ring. N,N~Dimethyl-N-propargylamine-benzimidedid not rearrange on heating; but the hydrobromide, on heating, disproportionated to give 1-benzoyl~2,2,2-trimethylhydraziniumbromide and I-benzoyl-2,2~ dimethylhydrazine. l-Ally'l--l, I-dimethyl-2-benzoy-lhydrazinium bromide and 1~benzoy-1-2,2, 2-trimethy-lhydrazinium iodide both disproportionated to give l~benzoyl-2,2-dimethylhydrazine. Section 1 concludes with a discussion of the mechanisms of ally'lic migrations in amineimides proposed by J. E. Baldwin. Section 2 deals with the formation of five-membered heterocyclic compounds from amineimides by bromination. 1,1-Dimethyl-2benzoyl- 4-bromopyrazolidinium bromide was formed from N-allyl-N,Ndime thy-lamtne-benzimide , 1,1-dimethyl-2-benzoyl-4-bromopyrazol-3enium bromide from N,N~dimethyl-N-propargylamine~benzimidevia the unusual acetylenic "bromonium" ion. Hydrogenolysis of both heterocyclic compounds gave the same product. The preparation was extended by forming 2,2-dimethyl-4-bromoisoxazolinium bromide from N-allylN, N-dimethylamine-N-oxide. Sections 3 and 4 cover a number of unsuccessful attempts to synthesise other amineimides and l,2-dipolar species.

The versatility and utilization of phosphorus based compounds in classic carbon-carbon bond forming and esterification reactions

The phosphonium salt room temperature ionic liquid tetradecyltrihexylphosphonium chloride (THPC) has been employed as an efficient reusable media for the palladium catalyzed Suzuki cross-coupling reaction of aryl halides, including aryl chlorides, under mild conditions. The cross-coupling reactions were found to proceed in THPC containing small amounts ofwater and toluene (single phase) using potassium phosphate and 1% Pd2(dba)3'CHCI3. Variously substituted iodobenzenes, including electron rich derivatives, reacted efficiently in THPC with a variety of arylboronic acids and were all complete within 1 hour at 50°C. The corresponding aryl bromides also reacted under these conditions with the addition of a catalytic amount of triphenylphosphine that allowed for complete conversion and high isolated yields. The reactions involving aryl chlorides were considerably slower, although the addition of triphenylphosphine and heating at 70°C allowed high conversion of electron deficient derivatives. Addition of water and hexane to the reaction products results in a triphasic system, from which the catalyst was then recycled by removing the top (hexanes) and bottom (aqueous) layers and adding the reagents to the ionic liquid which was heated again at 50°C; resulting in complete turnover of iodobenzene. Repetition of this procedure gave the biphenyl product in 82-97% yield (repeated five times) for both the initial and recycled reaction sequences. IL ESTERIFICATIONREACTION A new class oftrialkylphosphorane has been prepared through reaction of a trialkylphosphine with 2-chlorodimethylmalonate in the presence oftriethylamine. These new reagents promote the condensation reaction of carboxylic acids with alcohols to provide esters along with trialkylphosphine oxide and dimethylmalonate. The condensation reaction of chiral secondary alcohols can be controlled to give either high levels of inversion or retention through a subtle interplay involving basicity of the reaction media, solvent, and tuning the electronic and steric nature of the carboxylic acid and stenc nature of the phosphorane employed. A coherent mechanism is postulated to explain these observations involving reaction via an initial acyloxyphosphonium ion.

Phospha-adamantane ligands and phosphorous ionic liquids for palladium-catalyzed cross-coupling reactions /

New and robust methodologies have been designed for palladiumcatalyzed cross-coupling reactions involving a library of novel tertiary phosphine ligands incorporating a phospha-adamantane framework. The secondary phosphine, l,3,5,7-tetramethyl-2,4,8-trioxa-6-phospha-adamantane was converted into a small library of tertiary phosphine derivatives and the ability of these tertiary phosphaadamantanes to act as effective ligands in the palladium-catalyzed amination reaction and p-alkyl-Suzuki cross-coupling was examined. l,3,5,7-Tetramethyl-6- phenyl-2,4,8-trioxa-6-phosphaadamantane (PA-Ph) used in combination with Pd2(dba)3 CHCI3 facilitated the reaction of an array of aryl iodides, bromides and chlorides with a variety secondary and primary amines to give tertiary and secondary amines respectively in good to excellent yields. 8-(2,4-Dimethoxyphenyl)- l,3,5,7-tetramethyl-2,4,6-trioxa-8-phospha-tricyclo[3.3.1.1*3,7*]decane used in combination with Pd(0Ac)2 permitted the reaction of an array of alkyl iodides, and bromides with a variety aryl boronic acids and alkyl 9-BBN compounds in good to excellent yields. Subsequent to this work, the use of phosphorous based ionic liquids, specifically tetradecyltrihexylphosphonium chloride (THPC), in the Heck reaction provided good to excellent yields in the coupling of aryl iodides and bromides with a variety of olefins.

Reactions of steroidal epoxides with strong organic bases and an investigation into the syntheses of some labelled pregnane derivatives

Reactions of 5,6- and 4,5-epoxycholestane derivatives with strong bases were investigated. Epoxidation of 3a-acetoxycholest-5-ene also gave a new compound along with the anticipated epoxides. Interconversions of the latter were observed. Some possible mechanisms of its formation and rearrangements have been pIioposed. No reaction was observed with any of the 5,6- and 4,5-steroidal epoxides employed in the present study, using potassium tertiary butoxide under refluxing conditions. n-Butyllithium reacted only with 5,6-epoxycholestanes bearing a ketal moiety at the C3 carbon. Opening of the ketal group was observed with n-butyllithium in the case of a ~-epoxide. The reaction was also investigated in the absence of epoxide functionality. A possible mechanism for the opening of ketal group has been proposed. Lithium diethylamide (LDEA) was found effective in rearranging 5,6- and 4,5-epoxides to their ~orresponding allylic alcohols. These rearrangements presumably proceed via syn-eliminations, however the possibility of a corresponding anti-elimination has not been eliminated. A substituent effect of various functional groups (R = H, OH, OCH2CH20) at C3 has-been observed on product distribution in the LDEApromoted rearrangements of the corresponding epoxides. No reaction of these epoxides was observed with lithium diisopropylamide (LDA) • In the second part of the project, several attempts were made towards the sYRthesis of deoxycorticoste~one~17,2l,2l~d3' a compound desirable for the 2l-dehydroxylation studies of deoxycorticosterone. Several routes were investigated, and some deuterium labelled pregnane derivatives were prepared in this regard. Microbial 21-hydroxylation of progesteronel7,21,21,2l- d4 by ~ niger led to loss of deuterium from C21 of the product. An effort was made to hydroxylate progesterone microbially under neutral condtions.

Reactions of various aromatic nitro-compounds and anthraquinones with selected bases and nucleophiles

The Introducti on deals mainly with hi storical studies on aryne chemi stry and ring closure via arynes , hydride replacement from aromatic rings by nucleophi les, c l eavage of anthr aquinones in basic medium and the Leuckart reaction . This work can be divided into two main s ect i ons. Section I is concerned with the investigation of t he reaction of some aromatic ni t ro-compounds with potassamide in l iquid ammonia. 3-Amino-4- nitrobenzophenone was obtained from the reacti on of 4-nitrobenzophenone with t his reagent, toge t her with benzoic acid formed in a competing Haller-Bauer reaction. Nitrobenzene under these conditions gave a complex mixture from which 2-phenylphenol was isolated; a reaction i nvolving benzyne may be i nvo l ved. 4-Nitrodiphenyl sulfone gave 4-aminodiphenyl sulfone and 4-nitroani l ine. 4-Ethoxydiphenyl sulfone and 4-ethoxynitrobenzene were isolated when ethanol was used as a co-solvent in the reaction. Oxidative coupling reactions were observed with nitrotoluenes. 4-Nitrotoluene gave 4,4t-dinitrobibenzyl which i n a pro longed reaction gave 4,4t-dinitros t ilbene . 2-Nitrotoluene gave 2 , 2 t-dinitrobibenzyl, but not the corresponding stilbene derivative even after a longer time . A rather i nteresting result was obtained with 1-nitro-2,4,6- trimethylbenzene which gave a stilbene derivative only. Also the corresponding stilbene was obtained from bis-(4-nitrophenyl)-methane in a rather slow r eaction with this reagent . Section II deals wi th (i) the preparation of 5-chloro- 1-N-methyl aminoanthraquinone and a new synthesis of N-methyl acridones and (ii) treatment of chloro-anthraquinones with fo rmamide and a new synthesis of chloro-anthracenes . 5-Chloro-1 -N-methylaminoanthraqui none was synthesised f rom 1,5-dichloroanthraquinone by treatment with N-methylformamide. Treatment of 5-chloro-1-N-methylaminoanthraquinone with potassamide in liquid ammonia or with potassium t-butoxide i n t-butylbenzene gave N-methylacridone-1-carboxylic acid. This pleasing result, t he outcome of r i ng opening and alter native ring closure, is being extended to related ring systems.

An examination of NHL fans' reactions to the cancelled 2004-2005 season

AN EXAMINATION OF NHL FANS' REACTIONS TO THE CANCELLED 2004- 2005 SEASON Chad Asselstine Faculty of Applied Health Sciences, Brock University Gary Bettman, the Commissioner of the National Hockey League (NHL) stepped in front of the worldwide media on February 16, 2005 to announce that there would be no NHL games played during the 2004-2005 season. Two sides were prominent during the labour dispute; the NHL owners and the NHLP A, however a third side that became the forgotten party was the fans (NHLF A, 2005). The fans are the consumers of the NHL and all the brands associated with its franchises, they are the people who provide the revenues that allow owners to pay the players' salaries. The present study is situated within the sport marketing framework, particularly within the fan loyalty literature to provide an understanding of the impact of the 2004- 2005 lockout on the forgotten party, NHL fans. This study examines 16 fans' experiences in four stages: becoming a fan of the NHL, being a fan prior to the lockout, being a fan during the lockout including their anticipated reaction to the return of the NHL, and their actual reaction to the return of the NHL. Data was collected using face-to-face interviews with each ofthe participants, resulting in 16 fans' stories of how the lockout impacted them specifically. Through analysis of the data themes began to emerge including the fans' understanding that there was a need to restructure game play, the business operations of the NHL, a desire for service recovery strategies which would exceed fans' expectations, 4 and the desire for alternative forms of consumption including alternative hockey leagues as well as the growing popularity of poker playing. The study summarizes the effects that the NHL lockout had on the relationship between 16 individual fan~ and their favourite teams, and concludes with Suggestions for Future Research and Implications for Sport Marketers that emerged from this unique case in the history of North American professional sport.

Stock market reactions to changes in the FTSE SmallCap and S&P/TSX SmallCap indices

Stocks added to (deleted from) the Russell 2000 and the S&P 600 indexes experience positive (negative) abnormal returns following the announcement. However, researchers disagree on whether these abnormal returns are permanent or temporary and offer competing explanations. I address this controversy by examining market reactions for firms that are added to or deleted from the FTSE Small Cap index (the main testing sample) and the S&P/TSX SmallCap index (the comparison sample). For the main testing sample, all stocks except pure additions, experience a permanent price change that is accompanied by a permanent change in liquidity. However, for the comparison sample, abnormal returns over the announcement period fully reverted within 30 days. In further examination of stock liquidity for the main testing sample, sample stocks experience permanent change in liquidity. Taken together, the observed results support the price pressure and liquidity hypotheses.

Molybdenum (IV) imido silylamido and hydride complexes : stoichiometric and catalytic reactivity, mechanistic aspects of hydrosilation reactions

This thesis describes the synthesis, structural studies, and stoichiometric and catalytic reactivity of novel Mo(IV) imido silylamide (R'N)Mo(R2)(173_RIN-SiR32-H)(PMe3)n (1: Rl = tBu, Ar', Ar; R2 = Cl; R32 = Me2, MePh, MeCl, Ph2, HPh; n = 2; 2: R' = Ar, R2 = SiH2Ph, n = 1) and hydride complexes (ArN)Mo(H)(R)(PMe3)3 (R = Cl (3), SiH2Ph (4». Compounds of type 1 were generated from (R'N)Mo(PMe3)n(L) (5: R' = tBu, Ar', Ar; L = PMe3, r/- C2H4) and chlorohydrosilanes by the imido/silane coupling approach, recently discovered in our group. The mechanism of the reaction of 5 with HSiCh to give (ArN)MoClz(PMe3)3 (8) was studied by VT NMR, which revealed the intermediacy of (ArN)MCh(172 -ArN=SiHCl)(PMe3)z (9). The imido/silyl coupling methodology was transferred to the reactions of 5 with chlorine-free hydrosilanes. This approach allowed for the isolation of a novel ,B-agostic compound (ArN)Mo(SiHzPh)(173 -NAr-SiHPhH)(PMe3) (10). The latter was found to be active in a variety of hydrosilation processes, including the rare monoaddition of PhSiH3 to benzonitrile. Stoichiometric reactions of 11 with unsaturated compounds appear to proceed via the silanimine intermediate (ArN)M(17z-ArN=SiHPh)(PMe3) (12) and, in the case of olefins and nitriles, give products of Si-C coupling, such as (ArN)Mo(R)(173 -NAr-SiHPh-CH=CHR')(PMe3) (13: R = Et, R' = H; 14: R = H, R' = Ph) and (ArN)Mo(172-NAr-SiHPh-CHR=N)(PMe3) (15). Compound 13 was also subjected to catalysis showing much improved activity in the hydrosilation of carbonyls and alkenes. Hydride complexes 3 and 4 were prepared starting from (ArN)MoCh(PMe3)3 (8). Both hydride species catalyze a diversity of hydrosilation processes that proceed via initial substrate activation but not silane addition. The proposed mechanism is supported by stoichiometric reactions of 3 and 4, kinetic NMR studies, and DFf calculations for the hydrosilation of benzaldehyde and acetone mediated by 4.

Market reactions to changes in the Nasdaq-100 Index membership

We examine stock market reactions around the Nasdaq-100 Index reconstitutions. We find a symmetric and transitory price response accompanied by a significant increase in trading volume on the effective date. Firms added to the Nasdaq-100 Index experience significant increases in institutional ownership, the number of market makers, and the number of shareholders. In contrast, firms removed from the index show significant decreases in the number of institutional shareholders. Additions to the Nasdaq-100 Index also show significant increases in four liquidity measures, whereas deletions demonstrate significant decreases in two liquidity measures. These changes in liquidity are related to the abnormal return on the announcement day. Taken together, the results suggest support for the price pressure, liquidity, and investor awareness hypotheses.

Compensatory Arm Reactions in Individuals with Parkinson’s Disease

This study examined how perturbation-evoked compensatory arm reactions in individuals with Parkinson’s disease (PD) are influenced by explicit verbal instruction. Ten individuals with PD and 15 older adults without PD responded to surface translations with or without specific instruction to reach for and grasp the handrail. Electromyographic (EMG) and kinematic recordings were taken from the reaching arm. Results showed that individuals with and without PD benefitted similarly from explicit instruction. Explicit instruction resulted in earlier (p=0.005) and larger (p<0.001) medial deltoid EMG responses in comparison to no specific instructions. Compensatory arm reactions also occurred with a higher peak medio-lateral wrist velocity (p<0.001) and higher peak shoulder abduction angular velocity (p<0.001) with explicit instruction. Explicit instruction positively influenced compensatory arm reactions in individuals with and without PD. Future research is needed to determine whether the benefits of instruction persist over time and translate to a loss of balance in real life.

Application of thermal ion-molecule reactions in tackling spectroscopic inferences in inductively coupled plasma mass spectrometry

Part I: Ultra-trace determination of vanadium in lake sediments: a performance comparison using O2, N20, and NH3 as reaction gases in ICP-DRC-MS Thermal ion-molecule reactions, targeting removal of specific spectroscopic interference problems, have become a powerful tool for method development in quadrupole based inductively coupled plasma mass spectrometry (ICP-MS) applications. A study was conducted to develop an accurate method for the determination of vanadium in lake sediment samples by ICP-MS, coupled with a dynamic reaction cell (DRC), using two differenvchemical resolution strategies: a) direct removal of interfering C10+ and b) vanadium oxidation to VO+. The performance of three reaction gases that are suitable for handling vanadium interference in the dynamic reaction cell was systematically studied and evaluated: ammonia for C10+ removal and oxygen and nitrous oxide for oxidation. Although it was able to produce comparable results for vanadium to those using oxygen and nitrous oxide, NH3 did not completely eliminate a matrix effect, caused by the presence of chloride, and required large scale dilutions (and a concomitant increase in variance) when the sample and/or the digestion medium contained large amounts of chloride. Among the three candidate reaction gases at their optimized Eonditions, creation of VO+ with oxygen gas delivered the best analyte sensitivity and the lowest detection limit (2.7 ng L-1). Vanadium results obtained from fourteen lake sediment samples and a certified reference material (CRM031-040-1), using two different analytelinterference separation strategies, suggested that the vanadium mono-oxidation offers advantageous performance over the conventional method using NH3 for ultra-trace vanadium determination by ICP-DRC-MS and can be readily employed in relevant environmental chemistry applications that deal with ultra-trace contaminants.Part II: Validation of a modified oxidation approach for the quantification of total arsenic and selenium in complex environmental matrices Spectroscopic interference problems of arsenic and selenium in ICP-MS practices were investigated in detail. Preliminary literature review suggested that oxygen could serve as an effective candidate reaction gas for analysis of the two elements in dynamic reaction cell coupled ICP-MS. An accurate method was developed for the determination of As and Se in complex environmental samples, based on a series of modifications on an oxidation approach for As and Se previously reported. Rhodium was used as internal standard in this study to help minimize non-spectral interferences such as instrumental drift. Using an oxygen gas flow slightly higher than 0.5 mL min-I, arsenic is converted to 75 AS160+ ion in an efficient manner whereas a potentially interfering ion, 91Zr+, is completely removed. Instead of using the most abundant Se isotope, 80Se, selenium was determined by a second most abundant isotope, 78Se, in the form of 78Se160. Upon careful selection of oxygen gas flow rate and optimization ofRPq value, previous isobaric threats caused by Zr and Mo were reduced to background levels whereas another potential atomic isobar, 96Ru+, became completely harmless to the new selenium analyte. The new method underwent a strict validation procedure where the recovery of a suitable certified reference material was examined and the obtained sample data were compared with those produced by a credible external laboratory who analyzed the same set of samples using a standardized HG-ICP-AES method. The validation results were satisfactory. The resultant limits of detection for arsenic and selenium were 5 ng L-1 and 60 ng L-1, respectively.

Experimental and Computational Studies on Copper and Hydrobenzoin Derivatives in Catalytic Asymmetric Reactions

The use of theory to understand and facilitate catalytic enantioselective organic transformations involving copper and hydrobenzoin derivatives is reported. Section A details the use of theory to predict, facilitate, and understand a copper promoted amino oxygenation reaction reported by Chemler et al. Using Density Functional Theory (DFT), employing the hybrid B3LYP functional and a LanL2DZ/6-31G(d) basis set, the mechanistic details were studied on a N-tosyl-o-allylaniline and a [alpha]-methyl-[gamma]-alkenyl sulfonamide substrate. The results suggest the N-C bond formation proceeds via a cisaminocupration, and not through a radical-type mechanism. Additionally, the origin of diastereoselection observed with [alpha]-methyl-[gamma]-alkenyl sulfonamide arises from avoidance of unfavourable steric interactions between the methyl substituent and the N -protecting group. Section B details the computationally guided, experimental investigation of two hydrobenzoin derivatives as ligands/ catalysts, as well as the attempted synthesis of a third hydrobenzoin derivative. The bis-boronic acid derived from hydrobenzoin was successful as a Lewis acid catalyst in the Bignielli reaction and the Conia ene reaction, but provided only racemic products. The chiral diol derived from hydrobenzoin successfully increased the rate of the addition of diethyl zinc to benzaldehyde in the presence of titanium tetraisopropoxide, however poor enantioinduction was obseverved. Notably, the observed reactivity was successfully predicted by theoretical calculations.

Mirroring Enzymes: The Role of H-Bonding In HQuin-BAM Catalyzed Asymmetric Aza-Henry Reactions: A DFT Study into the Reactivity, Mechanism, and Origins of Selectivity

The exact mechanistic understanding of various organocatalytic systems in asymmetric reactions such as Henry and aza-Henry transformations is important for developing and designing new synthetic organocatalysts. The focus of this dissertation will be on the use of density functional theory (DFT) for studying the asymmetric aza-Henry reaction. The first part of the thesis is a detailed mechanistic investigation of a poorly understood chiral bis(amidine) (BAM) Brønsted acid catalyzed aza-Henry reaction between nitromethane and N-Boc phenylaldimine. The catalyst, in addition to acting as a Brønsted base, serves to simultaneously activate both the electrophile and the nucleophile through dual H-bonding during C-C bond formation and is thus essential for both reaction rate and selectivity. Analysis of the H-bonding interactions revealed that there was a strong preference for the formation of a homonuclear positive charge-assisted H-bond, which in turn governed the relative orientation of substrate binding. Attracted by this well-defined mechanistic investigation, the other important aspect of my PhD research addressed a detailed theoretical analysis accounting for the observed selectivity in diastereoselective versions of this reaction. A detailed inspection of the stereodetermining C-C bond forming transition states for monoalkylated nitronate addition to a range of electronically different aldimines, revealed that the origins of stereoselectivity were controlled by a delicate balance of different factors such as steric, orbital interactions, and the extent of distortion in the catalyst and substrates. The structural analysis of different substituted transition states established an interesting dependency on matching the shape and size of the catalyst (host molecule) and substrates (guest molecules) upon binding, both being key factors governing selectivity, in essence, offering an analogy to positive cooperative binding effect of catalytic enzymes and substrates in Nature. In addition, both intra-molecular (intra-host) and inter-molecular (host-guest, guest-guest) stabilizing interactions play a key role to the high π-facial selectivity. The application of dispersion-corrected functionals (i.e., ωB97X-D and B3LYP-D3) was essential for accurately modeling these stabilizing interactions, indicating the importance of dispersion effects in enantioselectivity. As a brief prelude to more extensive future studies, the influence of a triflate counterion on both reactivity and selectivity in this reaction was also addressed.