N. S. Vostrikov

Synthesis and some transformations of (−)-carveol

Reduction of the oxo group in (−)-carvone with LiAlH4, NaBH4, and (i-Bu)2AlH was performed. It was found that the reduction with the system CeCl3 · 7 H2O-NaBH4 in methanol at 20°C is the most practical procedure for the synthesis of (−)-carveol. Solvolysis of (−)-carvyl methanesulfonate gave products of SN2 and SN2′ replacement of the methylsulfonyloxy group, the latter slightly prevailing. Overman rearrangement of (−)-carveol resulted in the formation of the corresponding trichloroacetamide derivative, and intramolecular iodoetherification of the title compound afforded 6-iodomethyl-2,6-dimethyl-7-oxabicyclo[3.2.1]oct-2-ene.

Some transformations of (-)-(1S, 4R)-1-vinyl-7,7-dimethyl-bicyclo[2.2.1]heptan-2-one

Reactions were studied of (-)-(1S,4R)-1-vinyl-7,7-dimethylbicyclo[2.2.1]heptan-2-one with ethyl acetate lithium derivative, potassium acetylide, ozone, with a system OsO4-N-methylmorpholine N-oxide, and some subsequent transformations of the products obtained.

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.

Cautions in the synthesis of prostaglandins. C9→C15 acetate migration

In the present communication we would like to focus on some difficulty which may be encountered in the final steps of the classical prostaglandin E1 synthesis through enone I (Scheme 1) [1–5]. This approach implies a sequence of reactions, namely reduction of the keto group in enone I to hydroxy, protection of diol IV as bis-tetrahydropyranyl (THP) ether, hydrolysis of the acetate and ester groups, oxidation of the 9-hydroxy group, and removal of the THP protecting groups. The synthesis of PGE1 according to this reaction sequence was described in [6]. The necessity of careful adherence to the conditions at the step of protection of diol IV should also be noted. It is desirable to use freshly distilled anhydrous reagents and solvents and ensure fairly fast reaction completion (in ~1–2 h). In some experiments during the THP protection of diol IV, especially when the reaction was slow, partial migration of the acetyl group from C to C with formation of C-acetate VI was possible (Scheme 2). The resulting bis-THP ethers V and VI were mixtures of diastereoisomers detected as a diffuse spot by TLC. After alkaline hydrolysis, Collins oxidation, and deprotection of the hydroxy groups, that mixture was converted into a mixture of PGE1 and enone VII which cannot be separated by silica gel chromatography. When mixture V/VI was subjected in succession to alkaline and acid hydrolysis, prostaglandin F1α (VIII) was obtained with a good overall yield. Examples of 1,2 and long-range acyl group migrations, including those occurring in prostaglandins, have been well documented [7–11]. However, despite obvious structural and functional differences between PGE1 and enone VII, it is surprising that these compounds are characterized by very similar Rf values in TLC with different eluent systems and that they almost cannot be separated by chromatography using simple columns with different lengths and efficiencies. ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 1, pp. 140–142.

Synthesis of (5S)-5-methylfuran-2(5H)-one and its dihydro derivative

Abstract(5S)-5-Methylfuran-2(5H)-one and (5S)-5-methyltetrahydrofuran-2-one were synthesized starting from L-lactic acid ethyl ester.

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.

Oxidative dimerization of vinylbornylacetylenes under the action of mercuric acetate

Vinylbornylacetylenes and their trimethylsilyl derivatives undergo oxidative dimerization in the presence of an Hg(OAc)2—HgO system in MeOH to give the corresponding diacetylenes.

Formation of isomeric iodohydrins from terminal alkenes upon oxidation by a RuCl3-NaIO4 system

RuCl3-catalyzed periodate oxidation of alkenes affords isomeric iodohydrins.