P. Camps, Diana Marina Gorbig, Victòria Muñoz-Torrero
1997
Citations
0
Influential Citations
3
Citations
Journal
Collection of Czechoslovak Chemical Communications
Abstract
(5α,9α,11β)-11-Hydroxy-6,7,8,9-tetrahydro-5 H -5,9-propanobenzo[7]annulen-7-one ethylene ketal ( 6a ) and its 11α-methyl derivative ( 6b ) were prepared from monoketal 3 . These compounds underwent acid-catalyzed transannular reactions leading to 6,7,8,9-tetrahydro-5 H -5,9-propanobenzo[7]annulene derivatives 5a , 8a and 5b , 8b , respectively, depending on the reaction conditions. The compounds 6a and 6b were dehydrated to 6,7,8,9-tetrahydro-5H-5,9-prop[1]enobenzo[7]annulen-7-one ( 9a ) and its 11-methyl derivative ( 9b ), respectively. The conformational analysis of the 5,9-propanobenzo[7]annulene derivatives by molecular mechanics calculations (MM3 program) and the 1 H NMR data show that hydroxyketal 6a and the related compound (5α,7β,9α)-6,7,8,9-tetrahydro-5 H -5,9-propanobenzo[7]annulen-7-ol ( 4 ) exist mainly in the boat - chair conformation with the boat cycloheptenol ring, while for hydroxyketal 6b the chair - boat conformation ( chair cycloheptenol ring) seems to be the preferred one.