CYCLIZATION AND ALLYLIC REARRANGEMENT IN SOLVOLYSES OF MONOTERPENOIDS

Hydrolysis and methanolysis of chlorides, phosphates, and pyrophosphates are examined. Solvolyses of geranyl derivatives give predominantly acyclic primary and tertiary substitution products, and the SN1 reaction involves extensive allylic delocalization in the forming carbocation. Cyclic products formed with π participation predominate in solvolyses of neryl derivatives, but acyclic product formation involves allylic delocalization. The conformational requirements for πparticipation and allylic delocalization are different, and the rates, products, and kinetic secondary hydrogen isotope effects can be explained in terms of the initial state conformations and the transition state geometries. Decrease of solvent polarity favors elimination over substitution, and increasing nucleophilicity of the solvent favors formation of primary over tertiary products, but LiC1O4 has the opposite effect. These differences appear to depend upon the lifetime of the carbocation and its attaining the most stable conformat on. © 1979, American Chemical Society. All rights reserved.