V. Z. Vasikov

Prostanoids: XC. Extension to the Synthesis of Enprostil of the o-Nitrophenylsulfonylhydrazine Method for Transformation of 2-Propynyl Alcohols into Allenes

A potential precursor of enprostil, (±)-9-acetoxy-11,15-di-O-(tert-butyldimethylsilyl)-2-decarboxy-6-hydroxy-16-phenoxy-2-triphenylmethyloxymethyl-4,4,5,5-tetradehydro-17,18,19,20-tetranorprostaglandin F1α, was synthesized. This compound remained unchanged under the conditions for generation of allenes from 2-propynyl alcohols by the action of the system diisopropyl azodicarboxylate-triphenylphosphine-o-nitrophenylsulfonylhydrazine.

Double α-Ketol Rearrangement of (-)-1-{(1S,2R,4R)-1-Ethenyl-2-hydroxy-7,7-dimethylbicyclo[2.2.1]hept-2-yl}ethan-1-one

The title compound undergoes α-ketol rearrangement by the action of Lewis acids and bases to give the expected and double-rearrangement ring expansion products. Some specific features of the process are discussed.

Chiral exo-Alkylidenecyclopentanes from (1S,4R)-7,7-Dimethyl-1-vinylbicyclo[2.2.1]heptan-2-one

Abstract(1S,4R)-7,7-Dimethyl-1-vinylbicyclo[2.2.1]heptan-2-one oxime in the system (CF3CO)2O-CF3COOH and (1S,4R)-1-(1,2-dibromoethyl)-7,7-dimethylbicyclo[2.2.1]heptan-2-one in the system MeONa-MeOH undergo fragmentation to give exo-alkylidenecyclopentane derivatives, (4R)-4-cyanomethyl-5,5-dimethyl-1-[(1E)-trifluoroacetoxyethylidene]cyclopentane and isomeric (4R)-4-carboxymethyl-1-[(1ZE)-2-methoxyethylidene]-5,5-dimethylcyclopentanes, respectively. The trifluoroacetate derivative undergoes unusual rearrangement, yielding an equilibrium mixture of two isomers with endo- and exocyclic double bond.

1,2-Adducts of 5-Allyl-2,3,5-trichloro-4,4-dimethoxy-2-cyclopentenone with Ethyl Acetate Lithium Salt and Their Reactions with Iodine

The condensation of 5-allyl-2,3,5-trichloro-4,4-dimethoxy-2-cyclopentenone with ethyl acetate lithium salt generated in situ in THF at -78°C gave adducts at the carbonyl group, the corresponding cis- and trans-chlorohydrins. The steric structure of the products was determined by involving them into reaction with iodine. From the trans-adduct the expected bicyclic compound was obtained, while the cis-chlorohydrin underwent anomalous deacetalization to iodomethoxycyclopentenone. Spectral parameters of the adducts were discussed. Unusual diastereotopicity was observed for the remote methylene groups in the ester moiety.

Reaction of Lithiated 2-Trimethylsilyl-1,3-dithiane with (±)-Pantolactone

Pantolactone methoxymethyl ether reacted with lithiated 2-trimethylsilyl-1,3-dithiane to give the corresponding ketene dithioacetal and formal monoaddition product of silicon-free 2-lithio-1,3-dithiane at a ratio of 2:1. Possible ways of formation of the latter are discussed.

Specificity of the reaction of (−)-1-{(1S,2R,4R)-1-ethenyl-2-hydroxy-7,7-dimethylbicyclo[2.2.1]hept-2-yl}xethanone with ethenylmagnesium bromide

Ethenylmagnesium bromide (1.5 equiv) forms a chelate with (−)-1-{(1S,2R,4R)-1-ethenyl-2-hydroxy-7,7-dimethylbicyclo[2.2.1]hept-2-yl} ethanone in THF and promotes its fast primary α-ketol rearrangement into 1-ethenyl-2-hydroxy-2,8,8-trimethylbicyclo[3.2.1]octan-3-one. The latter reacts with excess magnesium reagent (0.5 equiv) according to common 1,2-addition pattern at the carbonyl group and is simultaneously involved in the second α-ketol rearrangement which leads to 1-ethenyl-3-hydroxy-3,8,8-trimethylbicyclo[3.2.1]octan-2-one as thermodynamically more stable regioisomer.

New 2,10-Functionalized Camphor Derivatives

Synthetic routes to precursors of tricyclic camphor derivatives fused at the 2,10-positions, the corresponding halohydrins and dimethyl acetal, are discussed.