The Meisenheimer rearrangement in heterocyclic synthesis. I. Synthesis of some tetrahydro-2,3-benzoxazepines

Abstract

Melt pyrolysis of the cis-6,7-dimethoxy-2-methyl-1-phenyl-1,2,3,4- tetrahydroisoquinoline N-oxide (2b) afforded the Meisenheimer rearrangement product, 7,8-dimethoxy-3-methyl-1-phenyl-1,3,4,5- tetrahydro-2,3-benzoxazepine (5b), in good yield, as did pyrolysis of the corresponding trans-N-oxide (3b) (in a melt) or a mixture of (2b) and (3b) (melt or in solution). The synthesis of the 1-deuterated analogue, (5c), of (5b) is described, together with products derived from (5b) by cleavage of the N-O bond which were used to confirm its structure. Meisenheimer rearrangement of the N-oxides (10) and (11) of 6,7-dimethoxy-1-(3,4-dimethoxyphenyl)-2-methyl-1,2,3,4-tetrahydroisoquinoline and 2-methyl-1-phenyl-1,2,3,4- tetrahydroisoquinoline gave the analogous 2,3-benzoxazepine derivatives (12) and (13), respectively.