Cyclopentanones—XVI : Prostaglandin synthesis involving catalytic hydrogenation of 2,3-dialkyl-4-hydroxy-2-cyclopentenones

2,3-Dialkyl-4-hydroxy-2-cyclopentenones with differently functionalised side chains yield predominantly all-cis 2,3-dialkyl-1-4,-dihydroxycyclopentanes on catalytic hydrogenation. Epimerisation at C-12 (PG numbering) leads to prostaglandin synthons. Influence of the side-chain functions on these reactions is described.     

Cyclopentanones—VIII : Stereochemistry of the lithium-liquid ammonia reduction of 2,3-dialkyl-4-hydroxy-2-cyclopentenones

2,3-Dialkyl-1,4-cyclopentanediols are obtained by lithium-liquidammonia-alcohol reduction of 2,3-dialkyl-4-hydroxy-2-cyclopentenones. The configuration of the diastereoisomers formed was proved by ¹H-NMR spectroscopy and by chemical evidence. In the most abundant isomer the alkyl groups are trans and each is in trans position to the vicinal hydroxyl function. In another diastereoisomer formed in substantial amount the alkyl groups have a cis orientation and are trans to the vicinal hydroxyl function. The ¹H-NMR parameters found are more useful generally for configurational assignments to synthetic and modified prostaglandins.     

Novel rearrangements of 4-silyl-3-buten-2-ones

Two 4-silyl-3-buten-2-ones, 2a and 2c, underwent an interesting rearrangement involving migration of the allyl or phenyl group on the silicon atom to the adjacent enone carbon when treated with various bases.     

Coupling of cyclopropylcarbene-chromium complex with ferrocenyl alkynes: synthesis of 5-ferrocenyl-5-hydroxy-2-cyclopentenones and 4-ferrocenyl-4-cyclopentene-1,3-diones

The coupling of ferrocenyl alkynes with cyclopropylcarbene-chromium complex leads to ferrocenyl-substituted 2-cyclopentenones with or without a hydroxy substituent, namely 4-cyclopentene-1,3-diones, 2-cyclobutenones, and α,β-unsaturated aldehydes in varying amounts. The reaction initially produces a cyclopentadienone intermediate, then to the double bond of which, bearing a ferrocenyl group, addition of water occurs to afford hydroxy-substituted 2-cyclopentenones. In all the products, the hydroxy group ends up α to the ferrocenyl moiety. In contrast, where no addition of water occurs, the alkenic bond is reduced to give 2-cyclopentenones. A secondary reaction product, namely 4-cyclopentene-1,3-dione, is formed by hydrolysis of the cyclopentadienone intermediates.     

Ab initio molecular orbital study of the tautomerism of 4-hydroxy-2-pyridinone

Ab initio calculations were performed on 2,4-pyridinediol, 4-hydroxy-2-pyridinone, and 2hydroxy-4-pyridinone at the HF /3-21G level with full geometry optimization. Two conformations of the hydroxyl group were considered for each tautomer. Corrections for polarization functions, electron correlation, and zero point energy were made by comparison with previous calculations on 2- and 4-pyridinone tautomerism which included these contributions. The most stable structure is 4-hydroxy-2-pyridinone, in agreement with experiment. Relative to 4-hydroxy-2-pyridinone, the energies of the other tautomers are estimated to be 1.9 kcal/mol for 2,4-pyridinediol and 8.9 kcal/mol for 2-hydroxy-4-pyridinone. These are in accord with the experimental values 0.3 ± 1.9 and 10.6 ± 1.9 kcal/mol, respectively, deduced from equilibration studies of the tautomeric methyl derivatives.     

Novel catalytic rearrangements of 2-vinyl-1,3-thiazetidines

The thiazetidines (1) and (2) undergo a novel and high yielding rearrangement on hydrogenation with heterogeneous catalysis to give the thiazolidines (5) and (8) whilst reaction with the homogeneous catalyst Rh(Ph₃P)₃Cl results in the alternative high yielding rearrangement to give a thiazine.     

Conjugate addition to 5-phenylsulfinyl 2-substituted 2-cyclopentenones: A new route to 4,5-disubstituted 2-cyclopentenones

4,5-Disubstituted 2-cyclopentenones have been prepared by conjugate addition of nitroalkanes and of organocopper reagents to 5-phenylsulfinyl 2-substituted 2-cyclopentenones, followed by pyrolysis.     

Synthesis and molecular structure of 2-hydroxy-2-(p-nitrophenyl)ethyl morpholine-4-carbodithioate

2-Hydroxy-2-(p-nitrophenyl)ethyl morpholine-4-carbodithioate was synthesized by reaction of p-nitrophenyloxirane with carbon disulfide and morpholine, and its molecular structure was studied by the X-ray diffraction method.     

Synthesis and molecular structure of di(4-hydroxy-2,6-diisoborn-2-ylphenyl)methane

Di(4-hydroxy-2-{(1R*,2S*,4S*)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl}-6-{(1S*,2R*,4R*)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl})methane was synthesized by condensation of the meso-diastereomer of 2,6-diisobornylphenol with paraformaldehyde under acid catalysis. The product structure as a meso-forms was confirmed by XRD analysis.     

Morita-Baylis-Hillman reaction of masked 5-alkylidene-2-cyclopentenones: general entry to 5-alkylidene-2-(hydroxyalkyl)- 2-cyclopentenones

The reaction of masked 5-alkylidene-2-cyclopentenones with aldehydes catalyzed by tributylphosphine in the presence of phenol provided the corresponding Morita-Baylis-Hillman adducts, which were subjected to flash vacuum pyrolysis to afford 5-alkylidene-2-(hydroxyalkyl)-2-cyclopentenones.     

Mesogenic 4-alkoxy-2-hydroxy-4’-formylazobenzenes

Homologous 4-alkoxy-2-hydroxy-4’-formylazobenzenes (Alk = C₃H₇, C₆H₁₁, C₈H₁₇) were synthesized and were shown to produce monotropic nematic liquid crystalline phase. The products were characterized by electron absorption and ¹H and ¹³C NMR spectra. The effect of lateral hydroxy group on their mesomorphic properties was analyzed.     

4-hydroxy-2-quinolones. 33. Novel approach to synthesis of 1H-2-oxo-4-hydroxyquinoline-3-acetic acid

We propose a novel method for obtaining the methyl ester of 1H-2-oxo-4-hydroxyquinoline-3-acetic acid.Communication 32, see [1].Ukrainian Pharmaceutical Academy, Kharkov 310002. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 928–932, July, 1997.     

Caged trans-4-hydroxy-2-nonenal

[reaction: see text] A caged 4-hydroxy-2-nonenal (4-HNE) has been prepared and its photochemistry investigated. Upon photolysis, 1 releases 4-HNE in up to 100% yield. From these photolyses, 4-HNE could be isolated in up to 91% yield. 4-HNE is produced under either aerobic or anaerobic conditions. The caging strategy does not require prior preparation of 4-HNE and, therefore, represents a three-step synthetic route to the bioactive enal in 48% overall yield.     

Novel rearrangements of N-arylpyrrolyl sulphides

Base treatment of the pyrrolylthioacetate 2 and the pyrrolylthioacetonitrile 4 unexpectedly yielded a pyrrolo[2,1-b]thiazole 6 and 2-(α-cyano-2-nitrobenzyl)thiopyrrole ( 7 ), respectively.