Chemistry of carbanions. 33. Use of intramolecular alkylation for the stereospecific formation of a cis-decalone

Abstract

Na2S04. Filtration and concentration via rotary evaporation of the ether solution afforded an orange oil (2.74 g) which was distilled through a short-path column at 0.25 mm (bp 36-38 °C). A 2.14-g (0.0198 mol, 66%) fraction of 2 (white solid) was obtained which partially clogged the condenser and receiver elbow, mp 40.5-41.5 °C. GC analysis on the KOH-treated column showed the syn/anti ratio to be 2.2:97.8. Preparation of Tosylhydrazones. The lability of 1 and 2 in the presence of acid precluded acid-catalyzed formation of the respective tosylhydrazones. The respective tosylhydrazones were prepared by stirring equimolar quantities of p-toluenesulfonyl hydrazide and the ketone in absolute ethanol (1 g/25 mL) for 21-24 h (25 °C). A notable exception was 1, which within 5 min after mixing led to the precipitation of the desired tosylhydrazone; the resulting slurry was stirred for only 2 h before workup. The crude tosylhydrazone obtained from 2 upon removal of solvent was first chromatographed on silica gel (methylene chloride eluent) and then recrystallized from ethanol at 0 °C. The tosylhydrazone from 1 required only recrystallization from ethanol,4]heptan-5-one tosylhydrazone: 83%