Twelve differently substituted tricyclic hydroxy ketones 7, 8 with [5-5-x] (x = 5, 6, 7) combinations of ring sizes were prepared in a single step in 43-91% yields (10 examples with 74-91%) from the corresponding protected (2′-oxocycloalkyl)methyl-substituted cyclopentadienes 6, which were obtained by cocydization of the alkynes 5 with the β-dimethylamino-substituted α,β-unsaturated Fischer carbene complexes 4 in 38-81% yield (6 examples with 66-81%). In most cases, the cis,anti,cis-isomers anti-7 were the major products. While the twofold cis-fusion is favored by minimal ring strain, hydrogen bonding between the hydroxy and the carbonyl group probably favors the anti-configuration of the tricyclic skeletons. Acid-catalyzed dehydration of the hydroxy ketones anti-7aa, anti-7ba, anti-7ca afforded the corresponding tricyclic dienes 15aa/16aa, 15ba, and 15ca/16ca, respectively.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry