Optical rotatory dispersion studies—LXXXI stereochemical studies—XXVII
1963; Elsevier BV; Volume: 19; Issue: 6 Linguagem: Inglês
10.1016/s0040-4020(01)99347-0
ISSN1464-5416
AutoresCharles D. Beard, Carl Djerassi, J. Sicher, Flórián Sipos, Miloš Tichý,
Tópico(s)Organic Chemistry Cycloaddition Reactions
ResumoOptically active cis- and trans-2-methyl-4-t-butylcyclohexanone have been synthesized and equilibrated in an alkaline medium. The position of the equilibrium, as determined by optical rotatory dispersion or gas chromatographic measurements, agreed well with earlier published data in the racemic series. The optical rotatory dispersion curve of cis-2-methyl-4-butylcyclohexanone, a substance which has been used earlier to demonstrate the absence of a “2-alkyl ketone effect,” points towards a departure from the ordinary chair conformation, which does not seem to be associated with the bulky t-butyl substituent, but rather with a 2,4-diequatorial substitution pattern, since similar results were encountered with cis-2,4-dimethylcyclohexanone. Quantitative comparison of the optical rotatory dispersion molecular amplitude contributions of axially oriented 2-methylcyclohexanones (e.g., trans-2,6-dimethylcyclohexanone, trans-2-methyl-4-t-butylcyclohexanone, 2β- and 4β-methyl-3-keto-5α-steroids) indicates discrepancies, which are best interpreted in terms of conformational distortion.
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