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We report experiments aimed at defining the electronic effect in the face selection of the oxy-Cope rearrangement. The probe used is a 1,5-hexadiene system having a 5-fluoroadamant-2-ylidene substituent at one terminus. The product ratio shows a clear bias toward bond formation such that the antiperiplanar bond is the more electron-rich one.Sir: Face selection during addition to trigonal carbon is at the core of stereogenesis. The more obvious steric aspect of face selectivity was the first one studied, in 1952;' the possible presence of an electronic effect was not investigated until two decades later.2 These and other early researches were largely limited to reactions of nucleophiles with carbonyl compounds in which there was no opportunity to study the two contributions separately. A previous report3 from this laboratory demonstrated that 5substituted adamantan-2-ones 1-Y-X could be used as a new and effective probe for the study of electronic effects. in the addition of nucleophiles to trigonal carbon. The system is free from steric complications, and it can readily be converted into a host of other substrates for use in probing electronic effects in other types of reactions at trigonal centers.

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