Rearrangement products of some 1R,4R-2-arylidene-p-menthan-3-ones in acidic media, their structures, and conformational analysis

1R,4R-2-(4-Phenylbenzylidene)-p-menthan-3-one in acidic media undergoes rea rrangement with migration of the exocyclic double bond to the cyclohexane r ing to form three 2-(4-phenylbenzyl) derivatives of p-menthen-3-ones. The r eaction products differ in the location of the endocyclic double bond (Delt a(1) or Delta(4)) and in the configuration of the new chiral C(2) center in the resulting p-menth-4-en-3-ones. The configurations of the 1R,2R- and 1R ,2S-2-(4-phenylbenzyl)-p-menth-4-en-3-ones were established based on analys is of their H-1 NMR spectra in combination with calculations by molecular m echanics. The molecular conformations of these compounds as well as of some racemic 2-benzyl-p-menth-1-en-3-one derivatives were studied.