ABSTRACT
A highly efficient approach for the construction of indolizidines and quinolizidines bearing a bridged quaternary stereocenter has been established in a one-pot fashion using aldehydes, nitroalkenes, and cyclic ketimines with excellent enantioselectivities and in high yields. Moreover, this method could be applied to the synthesis of indolizidines in the gram scale.
Subject(s)
Aldehydes/chemistry , Alkaloids/chemical synthesis , Alkenes/chemistry , Imines/chemistry , Indolizidines/chemistry , Nitriles/chemistry , Quinolizidines/chemistry , Alkaloids/chemistry , Crystallography, X-Ray , Molecular Conformation , StereoisomerismABSTRACT
An organocatalytic cascade reaction was established for the construction of indoloquinolizidine derivatives bearing five contiguous stereocenters from readily available aliphatic aldehydes, nitroethylenes, and tryptamine. This one-pot process gave 30-55% overall yields with excellent d.r. (>20 : 1 in all cases) and ee (91-98%). Additionally, quaternary stereogenic carbon center-containing indoloquinolizidines were prepared through NBS-mediated cyclization of one of the intermediates.