Benzo- and Indoloquinolizines. 21. Allylic Strain Competition in 4b,5,6,7,8,8a,10,11,16,16b-Decahydrodibenzindoloquinolizine Isomers. Detection of Boat Conformers by Carbon-13 Nuclear Magnetic Resonance

Article abstract of DOI:10.1021/jo00339a011

The concept of allylic strain between the benzene or the indole ring and the benzylic carbon-carbon bond is used to explain the conformational equilibria in the 4b,5,6,7,8,8a,10,11,16,16b-decahydrodibenzindolo<2,3-a>quinolizine isomers, in 5,6,8,9-tetrahydro-14bH-benzindolo<2,3-a>quinolizine, and in their indole N-methyl analogues.The conformational changes were monitored by 13C chemical shifts.Boat conformers with bow-sprit-flagpole interactions between γ-positions show upfield shifts, whereas these are not observed for δ-interacting groups.