HOMOALLYLIC FREE RADICALS . A STUDY OF REARRANGEMENT OF 3,5-CYCLOCHOLESTANYL RADICAL TO CHOLESTERYL RADICAL

A study of the reaction of cholesteryl chloride (VI) and 3,5-cyclocholestan-6-yl chloride (VII) with triphenyltin hydride and with sodium biphenyl radical anion has been carried out. With each of these reducing agents, cholesteryl chloride yields only 5-cholestene (VIII). On the other hand, cyclocholestanyl chloride gives mixtures of 3,5-cyclocholestane (IX) and 5-cholestene with both reducing agents. The results have been interpreted in terms of the formation of intermediate classical radicals which have the option of rearrangement or capture. The addition of thiophenol to 6-methylenecyclocholestane (III) has been studied briefly. This gives a mixture of products which on treatment with Raney nickel leads to 6-methylcyclocholestane (IV) and 6-methyl-5-cholestene (V). The results demonstrate without question that cholesteryl radical is significantly more stable than cyclocholestanyl radical. © 1968, American Chemical Society. All rights reserved.