Synthesis of (+-)-Glaucine and (+-)-Neospirodinenone via an One-Pot Bischler-napieralski Reaction and Oxidative Coupling by a Hypervalent Iodine Reagent

摘要

Condensation of 3,4-dimethoxybenzeneethanamine (3d)and various benzeneacetic acids,i.e.,4a-e,via a practical and efficient one-pot Bischler-napieralski reaction,followed by NaBH_4 reduction,produced a series of 1-benzyl-1,2,3,4-tetrahydroisoquinolines,i.e.,5a-e,in satisfactory yields (Scheme 3).Oxidative coupling of the N-acyl and N-methyl derivatives 6a-e of the latter with hypervalent iodine ([IFh(CF_3COO)_2])yielded products with two different skeletons (Scheme 4).The major products from N-acyl derivatives 6a-c were (+-)-N-acylneospirodienones 2a-c,while the minor was the 3,4-dihydroisoquinoline 7.(+-)-Glaucine (1),however,was the major product starting from N-methyl derivative 6e.Possible reaction mechanisms for the formation of these two types of skeleton are proposed (Scheme 5).