N-Bridgehead polycyclic compounds by sequential rearrangement-annulation of isoxazoline-5-spirocyclopropanes. 6. A general synthetic method for 5,6-dihydro-7(8H)- and 2,3,5,6-tetrahydro-7(1H)-indolizinones
作者:Ernesto G. Occhiato、Antonio Guarna、Alberto Brandi、Andrea Goti、Francesco De Sarlo
DOI:10.1021/jo00041a027
日期:1992.7
The thermal rearrangement-annulation of isoxazoline-5-spirocyclopropanes 4a-e substituted with a chain bearing a carbonyl group affords, in one step, 5,6-dihydro-7(8H)-indolizinones 5a-e. The rearrangement-annulation of isoxazoline-5-spirocyclopropanes 4f-h substituted with a chlorine on the side chain affords, also in one step, 2,3,5,6-tetrahydro-7(1H)-indolizinones 5f-h. When the cyclopropane ring is fused to a cyclohexane, or when a cyclohexanone is present in the side chain of isoxazoline 4, the process leads to N-bridgehead tricyclic compounds. Short rection times, mild reaction conditions, complete regioselectivity, and good stereoselectivity are the valuable features of this strategy.