Organic reactions in ionic liquids:A new method for the synthesis of alkyl aryl sulfones by alkylation of sodium arenesulfinates with unactivated alkyl chlorides

A new method is reported for the synthesis of alkyl aryl sulfones by alkylation of sodium arenesulfinates with unactivated alkyl chlorides using ionic liquid based on 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4) mixed with water (2:1) as reaction media. The ionic liquid can be reused and the procedure gives the sulfones in moderate yields.

Organic reactions in ionic liquids: ionic liquid-promoted efficient synthesis of N-alkyl and N-arylimides

In the ionic liquids [Bmim][PF6] or [Bmim][BF4], a series of succinimide, maleimide and phthalimide derivatives were synthesized from corresponding anhydrides with a variety of primary amines in excellent yield.

Organic reactions in ionic liquids:An efficient method for selective S-alkylation of 2-mercaptobenzothia(xa)zole with alkyl halides

Ionic liquids based on 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) are used as reusable reaction medium in the selective S-alkylation of 2-mercaptobenzothia(xa)zole with alkyl halides in the presence of potassium carbonate. This procedure is convenient, efficient, and generally gives rise to the S-alkylated product exclusively.

Organic reactions in ionic liquids: N-alkylation of cyclic imides with alkyl halides promoted by potassium fluoride

An ionic liquid based on 1-butyl-3-methylimidazolium hexafluorophosphate is used as an efficient reusable reaction medium in the N-alkylation of cyclic imides with alkyl halides promoted by fluoride ion.

Organic reactions in ionic liquids: synthesis of alkyl aryl trithiocarbonates by the S-arylation of potassium carbonotrithioates with diaryliodonium salts

Various alkyl aryl trithiocarbonates were readily prepared in good yields by the S-arylation of potassium carbonotrithioates with diaryliodonium salts in the room-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4). The ionic liquid can be recycled and reused.

Organic reactions in ionic liquids; Ionic liquid-accelerated three-component reaction: a rapid one-pot synthesis of 3-alkyl-5-[(Z)-arylmethylidene]-1,3-thiazolidine-2,4-diones

A rapid one-pot synthesis of 3-alkyl-5-[(Z)-arylme­thylidene]-1,3-thiazolidine-2,4-dionesis described that occurs in recyclable ionic liquid [bmim]PF6 (1-butyl-3-methylimidazolium hexafluorophosphate).Significant rate enhancement and good selectivity have been observed.

Hypervalent iodine in synthesis 64:Syntheses of diaryl selenides and alkyl aryl selenides by palladium-catalyzed arylation of areneselenyl or alkaneselenyl magnesium bromide with diaryliodonium salt

Areneselenyl or alkaneselenyl magnesium bromide reacts rapidly with diaryliodonium salt to give the corresponding diaryl or alkyl aryl selenide in the presence of catalytic amounts of Pd-(PPh3)4 in good yield.

Conformational Evaluation of Indol-3-yl-N-alkyl-glyoxalylamides and Indol-3-yl-N,N-dialkyl-glyoxalylamides

Restricted rotation in indol-3-yl-N-alkyl- and indol-3-yl-N,N-dialkyl-glyoxalylamides can in principle give the syn-periplanar and anti-periplanar rotamers. In asymmetrically disubstituted glyoxalylamides, steric effects lead to the occurrence of both rotamers, as observed by NMR spectroscopy. The predominant peak corresponds with the anti rotamer, in which the bulkier alkyl group is orientated trans to the amide carbonyl group. In monoalkylated glyoxalylamides, only one set of peaks is observed, consistent with the presence of only one rotamer. Crystal structures of 5-methoxyindole-3-yl-N-tert-butylglyoxalylamide, indole-3-yl-N-tert-butylglyoxalylamide, and indole-3-yl-N-isopropylglyoxalylamide reported here reveal a syn conformation held by an intramolecular N-HO hydrogen bond.

The icephobic performance of alkyl-grafted aluminum surfaces

This work analyzes the anti-icing performance of flat aluminum surfaces coated with widely used alkyl-group based layers of octadecyltrimethoxysilane, fluorinated alkylsilane and stearic acid as they are subjected to repeated icing/deicing cycles. The wetting properties of the samples upon long-term immersion in water are also evaluated. The results demonstrate that smooth aluminum surfaces grafted with alkyl groups are prone to gradual degradation of their hydrophobic and icephobic properties, which is caused by interactions and reactions with both ice and liquid water. This implies that alkyl-group based monolayers on aluminum surfaces are not likely to be durable icephobic coatings unless their durability in contact with ice and/or water is significantly improved.

Synthesis of multisubstituted halo -olefins via Pd-catalyzed cross -coupling reactions. Applications in nucleoside chemistry

The enzyme S-adenosyl-L-homocysteine (AdoHcy) hydrolase effects hydrolytic cleavage of AdoHcy to adenosine (Ado) and L-homocysteine (Hcy). The cellular levels of AdoHcy and Hcy are critical because AdoHcy is a potent feedback inhibitor of crucial transmethylation enzymes. Also, elevated plasma levels of Hcy in humans have been shown to be a risk factor in coronary artery disease. ^ On the basis of the previous finding that AdoHcy hydrolase is able to add the enzyme-sequestered water molecule across the 5',6'-double bond of (halo or dihalohomovinyl)-adenosines causing covalent binding inhibition, we designed and synthesized AdoHcy analogues with the 5',6'-olefin motif incorporated in place of the carbon-5' and sulfur atoms. From the available synthetic methods we chose two independent approaches: the first approach was based on the construction of a new C5'-C6' double bond via metathesis reactions, and the second approach was based on the formation of a new C6'-C7' single bond via Pd-catalyzed cross-couplings. Cross-metathesis of the suitably protected 5'-deoxy-5'-methyleneadenosine with racemic 2-amino-5-hexenoate in the presence of Hoveyda-Grubb's catalyst followed by standard deprotection afforded the desired analogue as 5' E isomer of the inseparable mixture of 9'R/S diastereomers. Metathesis of chiral homoallylglycine [(2S)-amino-5-hexenoate] produced AdoHcy analogue with established stereochemistry E at C5'atom and S at C9' atom. The 5'-bromovinyl analogue was synthesized using the bromination-dehydrobromination strategy with pyridinium tribromide and DBU. ^ Since literature reports on the Pd-catalyzed monoalkylation of dihaloalkenes (Csp2-Csp3 coupling) were scarce, we were prompted to undertake model studies on Pd-catalyzed coupling between vinyl dihalides and alkyl organometallics. The 1-fluoro-1-haloalkenes were found to undergo Negishi couplings with alkylzinc bromides to give multisubstituted fluoroalkenes. The alkylation was trans-selective affording pure Z-fluoroalkenes. The highest yields were obtained with PdCl 2(dppb) catalyst, but the best stereochemical outcome was obtained with less reactive Pd(PPh3)4. Couplings of 1,1-dichloro-and 1,1-dibromoalkenes with organozinc reagents resulted in the formation of monocoupled 1-halovinyl product. ^

Synthesis of multisubstituted halo-olefins via Pd-catalyzed cross-coupling reactions : applications in nucleoside chemistry

The enzyme S-adenosyl-L-homocysteine (AdoHey) hydrolase effects hydrolytic cleavage of AdoHcy to adenosine (Ado) and L-homocysteine (Hcy). The cellular levels of AdoHcy and Hcy are critical because AdoHcy is a potent feedback inhibitor of crucial transmethylation enzymes. Also, elevated plasma levels of Hcy in humans have been shown to be a risk factor in coronary artery disease. On the basis of the previous finding that AdoHcy hydrolase is able to add the enzyme-sequestered water molecule across the 5',6'-double bond of (halo or dihalohomovinyl)-adenosines causing covalent binding inhibition, we designed and synthesized AdoHcy analogues with the 5',6'-olefin motif incorporated in place of the carbon-5' and sulfur atoms. From the available synthetic methods we chose two independent approaches: the first approach was based on the construction of a new C5'- C6' double bond via metathesis reactions, and the second approach was based on the formation of a new C6'-C7' single bond via Pd-catalyzed cross-couplings. Cross-metathesis of the suitably protected 5'-deoxy-5'-methyleneadenosine with racemic 2-amino-5-hexenoate in the presence of Hoveyda-Grubb's catalyst followed by standard deprotection afforded the desired analogue as 5'E isomer of the inseparable mixture of 9'RIS diastereomers. Metathesis of chiral homoallylglycine [(2S)-amino-5-hexenoate] produced AdoHcy analogue with established stereochemistry E at C5'atom and S at C9' atom. The 5'-bromovinyl analogue was synthesized using the brominationdehydrobromination strategy with pyridinium tribromide and DBU. Since literature reports on the Pd-catalyzed monoalkylation of dihaloalkenes (Csp2-Csp3 coupling) were scarce, we were prompted to undertake model studies on Pdcatalyzed coupling between vinyl dihalides and alkyl organometallics. The 1-fluoro-1- haloalkenes were found to undergo Negishi couplings with alkylzinc bromides to give multisubstituted fluoroalkenes. The alkylation was trans-selective affording pure Zfluoroalkenes. The highest yields were obtained with PdCl 2(dppb) catalyst, but the best stereochemical outcome was obtained with less reactive Pd(PPh3)4 . Couplings of 1,1- dichloro-and 1,1-dibromoalkenes with organozinc reagents resulted in the formation of monocoupled 1-halovinyl product.

Influence of alkyl chain length on sulfated zirconia catalysed batch and continuous esterification of carboxylic acids by light alcohols

The impact of alkyl chain length on the esterification of C2–C16 organic acids with C1–C4 alcohols has been systematically investigated over bulk and SBA-15 supported sulfated zirconias (SZs). Rates of catalytic esterification for methanol with acetic acid are directly proportional to the sulfur content for both SZ and SZ/SBA-15, with the high dispersion of SZ achievable in conformal coatings over mesoporous SBA-15 confering significant rate-enhancements. Esterification over the most active 0.24 mmol gcat−1 bulk SZ and 0.29 mmol gcat−1 SZ/SBA-15 materials was inversely proportional to the alkyl chain length of alcohol and acid reactants; being most sensitive to changes from methanol to ethanol and acetic to hexanoic acids respectively. Kinetic analyses reveal that these alkyl chain dependencies are in excellent accord with the Taft relationship for polar and steric effects in aliphatic systems and the enthalpy of alcohol adsorption, implicating a Langmuir–Hinshelwood mechanism. The first continuous production of methyl propionate over a SZ fixed-bed is also demonstrated.