Reactions of Mixed-Valent Palladium (IV,II) Complexes of Tetradentate Schiff-Bases Involving Bond Isomerization

Reactions of [PdIVB-(AI)2]++ [PdIICl4]-- (i) B-(AI)2 = dianion of N,N'-ethylene-/i-propylene-/n-propylene-bis(acetyl-acetoneimine) with some π-acceptor ligands, aliphatic primary amines and nitrosating reagents have been investigated. In all these reactions except nitrosation, 1:1 adducts having the formula, [PdIVB-(AI)2.X] [PdIICl4] [X = triphenylphosphine (TPP), triphenylarsine (TPA), pyridine (Py), methylamine (CH3NH2) or ethylamine (C2H5NH2)] are obtained. The formation of these complexes is associated with a bond isomerization - from Pd-Cxo-π -allylic bond prevailing in [PdIVB-(AI)2]2+ to PdIV-O bonding.Reaction of (i) with nitrosating reagents reduces PdIV to PdII and subsequently transform the γ-CH group, into an ambidentate isonitroso group (°C = NOH). The latter enters into coordination with PdII by dislodging the already coordinated carbonyl group. Further, selective nitrosation (mono- and dinitrosation) has been carried out by controlling the amount of the nitrosating reagent and the reaction time. The complexes have been characterized by elemental analyses, electrical conductivity, magnetic susceptibility and ir spectral data.

Synthesis Based On Cyclohexadienes .6. A New Total Synthesis Of (+/-)-Methyl Acorate And (+/-)-Methyl Epi-Acorate

A new method of construction of carbon-carbon bond is described. Thus the dianions generated from the metal-ammonia reduction of substituted benzoic acids readily undergo Michael addition with methyl crotonate resulting in synthetically useful products having a quaternary carbon. Based on this strategy, new syntheses of (+/-)-methyl acorate (14b) and (+/-)-methyl epi-corate (15) are reported.

Synthesis Of (+/-)-2-Isopropyl-5,6-Dimethylbicyclo[3.2.1]Oct-6-En-8-One

Methanolic hydrogen chloride cyclization of the triketone 8, prepared from the Mannich base 7 and 2-methylcyclopentane-1,3-dione, gives ketones 9 and 10. NaBH4 reduction of 9 followed by Grignard reaction with CH3MgI affords the diol 12. Catalytic hydrogenation of 12 followed by PCC oxidation yields the ketoalcohol 13. Dehydration of 13 with SOCl2/pyridine results in a 1:1 mixture of the endo-14 and exo-15 olefins, separated by chromatography.

Synthesis Of (+/-)-Beta-Cuparenone Via 3-Oxa-Beta-Cuparenone

Grignard reaction followed by ozonolysis, or ozonolysis followed by Grignard reaction on the pentenoate 8, generates the diol 9. Cyclodehydration of 9 leads to the 3-oxacuparene (6), whereas PCC oxidation furnishes the 3-oxa-beta-cuparenone (7). Methanesulfonic acid-P2O5 transforms 7 into cyclopentenones 4, 5, known precursors to beta-cuparenone (3), and the naphthalenone 14.

Synthetic investigations on illudinine: a new synthesis of methyl 8-methoxy-2,2-dimethyl-7-oxo-1,2,3,5,6,7-hexahydro-s-indacene-4-carboxylate

A new strategy for the total synthesis of methyl 8-methoxy-2,2-dimethyl-7-oxo-1,2,3,5,6,7-hexahydro-s-indacene-4-carboxylate 4, a key intermediate in the synthesis of illudalanes, is reported. The key step in this strategy is a new method of preparation of indanones from tetralones. Thus, the furfurylidene derivative of 6-methoxy-3,4-dihydronaphthalen-1-(2H)-one is oxidised to the dicarboxylic acid 9a which is cyclodehydrated to methyl 7-methoxy-1-oxoindan-4-carboxylate 10. Similar reactions on the tetrahydronaphthalenone 25, obtained from 6-methoxy-1,2,3,4-tetrahydronaphthalene-7-carbaldehyde 11 by sequential transformations including a regiospecific benzylic oxidation resulted in the hexahydro-s-indacenone 4, thus completing a formal synthesis of illudinine 1.

Tandem Michael reaction. Synthesis of bridged diketones

Addition of NaOMe, NaOEt, or NaOPr(i) to dispironaphthalenone 1 resulted in the formation of diketones 4a-c and 5a-c. The structure assigned to 4a was confirmed by conversion to the known hemiacetal 3. Similar addition of carbon nucleophiles like diethyl malonate, dimethyl malonate, methyl cyanoacetate, and ethyl cyanoacetate afforded diketones 4d-g. Formation of these compounds has been rationalized.

Oxidation of aromatic substrates with hydrogen peroxide and hydrochloric acid

Chloroquinones are prepared conveniently from phenol, naphthols and aromatic amines.

The identification of 14 alpha,17 beta-dihydroxyandrost-4-en-3-one monohydrate and 14 alpha,17 beta-dihydroxyandrosta-1,4-dien-3-one monohydrate, metabolites of androstenedione in Mucor piriformis

The microorganism Mucor piriformis transforms androst-4-ene-3,17-dione into a major and several minor metabolites. X-ray crystallographic analysis of two of these metabolites was undertaken to determine unambiguously their composition and chirality. Crystals belong to the orthorhombic space-group P2(1)2(1)2(1), with a = 7.199(4) angstrom and a = 6.023(3) angstrom, b = 11.719(3) angstrom and b = 13.455(4) angstrom, c = 20.409(3) angstrom and c = 20.702(4) angstrom for the two title compounds, respectively. The structures have been refined to final R values of 0.060 and 0.040, respectively.

The influence of lone-pair repulsions on C–C bond lengths: a critical evaluation of the experimental and theoretical evidence

X-Ray structural data, as well as semiempirical and ab initio molecular orbital calculations, reveal no systematic and substantial difference between the C–C bond lengths of cis and trans 1,2-diketones. Additional results on various conformations of 1,2-diimines and 1,2-dithiones follow the same pattern. Therefore, lone-pair repulsions cannot be implicated in the observed lengthening of C–C bonds in isatin and several related molecules. Conjugation in these systems occurs peripherally avoiding the participation of the central C–C bond. Negative hyperconjugative interaction between the oxygen lone pairs and the adjacent C–C σ* orbital is suggested to be the principal reason for the relatively long C–C bond in diketones. This effect is found in both the cis and trans conformations.

Lewis Acid-Lewis Base Mediated Metal-Free Hydrogen Activation and Catalytic Hydrogenation

Organocatalysis, the use of organic molecules as catalysts, is attracting increasing attention as one of the most modern and rapidly growing areas of organic chemistry, with countless research groups in both academia and the pharmaceutical industry around the world working on this subject. The literature review of this thesis mainly focuses on metal-free systems for hydrogen activation and organocatalytic reduction. Since these research topics are relatively new, the literature review also highlights the basic principles of the use of Lewis acid-Lewis base pairs, which do not react irreversibly with each other, as a trap for small molecules. The experimental section progresses from the first observation of the facile heterolytical cleavage of hydrogen gas by amines and B(C6F5)3 to highly active non-metal catalysts for both enantioselective and racemic hydrogenation of unsaturated nitrogen-containing compounds. Moreover, detailed studies of structure-reactivity relationships of these systems by X-ray, neutron diffraction, NMR methods and quantum chemical calculations were performed to gain further insight into the mechanism of hydrogen activation and hydrogenation by boron-nitrogen compounds.

A new general method for the introduction of the aldehyde function in aromatic compounds

Side chain bromination of aromatic amidomethylated compounds yields aldehydes.

Crystal and Molecular Structure of N-acetyl-L-glutamine

The crystal and molecular structure of the title compound has been determined by direct methods from diffractometer data. Crystals are orthorhombic, with Z= 4 in a unit cell of dimensions : a= 13.811 (10), b= 5.095(5), c= 12.914(10)Å, space group P212121. The structure was refined by least-squares to R 3.31% for 868 observed reflections. There is significant non-planarity of the peptide group and its nitrogen atom is significantly pyramidal. There is no correlation between the double-bond character and reactivity of the C–N bond of the terminal amide group in glutamine and acetamide