Acid-induced transannular cyclization of 2-methyl- and 10-methyl-5-cyclodecenone

2-Methyl- and 10-methyl-5-cyclodecenone were made by anionic oxy-Cope rearrangement of the corresponding 1,2-divinylcyclohexanols, and their transannular cyclizations were induced using trifluoroacetic acid. In each case, a single diastereomer of a trans fused bicyclo[4.4.0]decan-1-ol with an equatorial methyl group was isolated. The methyl substituent at C2 or C10 of the 5-cyclodecenone did not alter the regio- and stereochemistry previously observed for the parent ring system, (E)-5-cyclodecenone. The relative stereochemistry of the products was determined spectroscopically from J-value analysis and NOE.