Synthesis of (±)‐Glaucine and (±)‐Neospirodienone via an One‐Pot BischlerNapieralski Reaction and Oxidative Coupling by a Hypervalent Iodine Reagent

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 ([IPh(CF 3 COO) 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 ).