Synthesis of azolo[a]pyridines from 5-(bromomethyl)hept-4-en-3-one and 5-bromopent-3-en-2-one derivatives

Alkyl derivatives of 1H-imidazo[1,2-a]pyridin-4-ium, 5H-pyrido[1,2-a]benzimidazol-10-ium, 1H-[1,2,4]-triazolo[4,3-a]pyridin-4-ium, and 3-methylthiazolo[3,2-a]pyridin-4-ium bromides were obtained in two stages from (4Z)-5-(bromomethyl)-2,2,6,6-tetramethylhept-4-en-3-one, 5-bromo-4-methylpent-3-en-2-one, or (3E)-5-bromopent-3-en-2-one by alkylation of 1-alkyl-1H-imidazoles, 1-alkyl-1H-benz-imidazoles, 1-methyl-1H-1,2,4-triazole, and 4-methylthiazole and subsequent cyclization of the quaternary azolium salts in the presence of bases.     

Enantioselective synthesis of (+)-3-oxabicyclo[3.2.0]hept-6-en-2-one

The title compound was obtained in 99.3% ee by enzymatic oxidation of cis-2-cyclobutene-1,4-bis(hydroxymethyl) in the presence of horse liver alcohol dehydrogenase. Another route was through desymmetrisation of cis-cyclobut-3-ene-1,2-dicarboxylic anhydride with (−)-pantolactone.     

BF3-induced cyclobutane-opening of verbenone and its deconjugate homolog. Efficient preparation of o-mentha-1,8-dien-3-one and o-menth-1-en-3-one in optically active forms

Starting with (+)-verbenone, readily obtainable from (+)-nopinone, enantioselective preparation of (S)-(+)-4-isopropenyl-, (S)-(−)-4-isopropyl- and (R)-(+)-4-(1-acetoxy-1-methylethyl)-3-methyl-2-cyclohexen-1-ones was accomplished with little loss of stereochemical integrity via BF₃-induced cyclobutane-opening of (+)-4-(methylene)nopinone. As we have developed an efficient chemical transformation of (+)-nopinone into (−)-verbenone, the present syntheses of the above cyclohexenones are formal syntheses of their enantiomers from (+)-nopinone.     

Efficient synthesis of 8-oxa-bicyclo[3.2.1]octane derivatives from d-arabinose

Our studies of the TIBAL-promoted Claisen rearrangement reaction and ring-closing metathesis (RCM) resulted in the development of an efficient synthetic route to polyfunctional seven-membered carbasugar synthons from d-arabinose. Moreover, the construction of 8-oxa-bicyclo[3.2.1]octane derivatives 10 and 13 was achieved by BCl₃ or iodide-promoted intramolecular electrophilic addition reactions, which were regio- and stereoselective.     

Novel dimerisation of bicyclo[3.3.0]oct-2-en-3-one

Application of the intramolecular Wadsworth-Emmons reaction to bicyclo[3..3.0]oct-2-en-3-ones results in the formation of a novel dimer (11) of the parent member (6) whose structure has been determined by X-ray crystallography.     

Epoxidation of 2-azabicyclo[2.2.1]hept-5-en-3-one

Epoxidation of 2-azabicyclo[2.2.1]hept-5-en-3-one has been performed in high yield with potassium hydrogen persulfate at pH 6, ¹H nmr data indicate an exo stereoconfiguration of the epoxide.     

Synthesis and Characterization of S-Methylspiro[4.5]-dec-7-en-6-one and 6-methylspiro[4.5]dec-6-en-8-one

In connection with another problem, we required authentic samples of 8-methylsiro[4.5]dec-7-en-6-one (1) and 6-methyl-spire[4.5]dec-6-en-8-one (2). The former compound is not reported in the literature. Although there are two reports of the latter material,^1,2 the physical data ascribed to it do not agree. In this communication, we report the synthesis and characterization of the two isomers.     

Synthesis of 7,7-dimethylbicyclo-[3.3.0]octane by acetylating a dicobaltohexacarbonyl 4-methylpent-3-en-1-yne complex

Dicobaltohexacarbonyl 4-methyl-pent-3-en-1-yne complexes have been acylated with acryloyl and crotonoyl tetrafluoroborates followed by methanolysis to make acylmethoxy adducts containing hem-dimethyl moieties. Conditions have been defined under which such adducts containing enone systems are selectively reduced to allyl acohols with retention of the cobaltocarbonyl moieties. The latter can be converted by Quand-Poson reaction to the inaccessible polyfunctional derivatives of 7,7-dimethylbicyclo[3.3.0]octane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1879–1888, August, 1989.     

手性3-氧杂双环[3.1.0]-己-2-酮类化合物的不对称合成

采用手性铜催化剂(S)-7644, 利用重氮醋酸不饱和酯的分子内不对称卡宾加成环化, 合成了七个光学活性3-氧杂双环[3.1.0]-己-2-酮类化合物。产品经元素分析、红外、核磁确证了结构, 并测定了比旋光度和光学收率。     

1H NMR studies of 3,8-dioxatricyclo-[3.2.1.02,4]octane derivatives

A series of 6-X-3,8-dioxatricyclo[3.2.1.0^2,4]octanes (X?CO₂CH₃, CN, Cl and CN) are studied by NMR, after their syntheses by epoxidation of the corresponding 7-oxabicyclo[2.2.1]heptenes. The NMR parameters (J, δ) are determined, and also the anisotropy effects of methyl groups at the 1,5 bridgehead positions. The results allow an unambiguous identification of the diastereo-isomers having a gem-chlorocyano group in the 6 position.     

Synthesis and structure of 2,4-di-tert-butyl-1-chloro-6-methyltricyclo[4.1.0.02,7]hept-4-en-3-one

The reaction of 2,6-di-tert-butyl-4-dichloromethyl-4-methylcyclohexa-2,5-dien-1-one with (Me₃Si)₂NNa yielded 2,4-di-tert-butyl-1-chloro-6-methyltricyclo[4.1.0.0^2,7]hept-4-en-3-one (substituted tropovalene). The structure of the title compound was established by¹H and¹³C NMR spectroscopy and X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1642–1645, September, 1997.     

Synthesis of phosphodiesterase IVb inhibitors 2. Stereoselective synthesis of hexahydro-3H-pyrrolo[1,2-c]imidazol-3-one and tetrahydro-1H-pyrrolo[1,2-c][1,3]oxazol-3-one derivatives

The total stereoselective synthesis of two highly potent phosphodiesterase IVb inhibitors from nitroethane, isovanillin, and ethyl vinyl ether was developed. The compounds obtained are the derivatives of hexahydro-3H-pyrrolo[1,2-c]imidazol-3-one and tetrahydro-1H-pyrrolo[1,2-c][1,3]oxazol-3-one. The strategy proposed involves silylation of six-membered cyclic nitronates as a key step leading to 5,6-dihydro-4H-1,2-oxazines with the group CH₂FG (FG = N₃ or OH) at the C(3) atom.