Novel Stereoselective Syntheses of the Fused Benzazepine Dopamine D1 Antagonist (6aS,13bR)-11-Chloro-6,6a,7,8,9,13b-hexahydro-7-methyl-5H- benzo[d]naphth[2,1-b]azepin-12-ol (Sch 39166): 1. Aziridinium Salt Based Syntheses
journal contributionposted on 26.04.1998, 00:00 authored by Richard W. Draper, Donald Hou, Radha Iyer, Gary M. Lee, Jimmy T. Liang, Janet L. Mas, Wanda Tormos, Eugene J. Vater, Frank Günter, Ingrid Mergelsberg, Dominik Scherer
Several novel enantioselective syntheses of the dopamine D1 antagonist (6aS,13bR)-11-chloro-6,6a,7,8,9,13b-hexahydro-7-methyl-5H-benzo[d]naphth[2,1-b]azepin-12-ol (2) are described in which the key intermediate was 1-(2,2-dimethoxyethyl)-1-methyl-1a,2,3,7b-tetrahydro-1H-naphth[1,2-b]aziridinium salt (20). The latter species was prepared either from 1-(2,2-dimethoxyethyl)-1a,2,3,7b-tetrahydro-1H-naphth[1,2-b]azirine (18) by methylation or from the tertiary amino alcohols 1-[(2,2-dimethoxyethyl)methylamino]-1,2,3,4-tetrahydro-2-naphthalenol (23) or 2-[(2,2-dimethoxyethyl)methylamino]-1,2,3,4-tetrahydro-1-naphthalenol (24) by tosylation and in situ ring closure. Regioselective trapping of 20 with Grignard reagent (4-chloro-3-methoxyphenyl)magnesium bromide (10) then afforded the trans amine 1-(4-chloro-3-methoxyphenyl)-N-(2,2-dimethoxyethyl)-1,2,3,4-tetrahydro-N-methyl-2-naphthalenamine (22), which was cyclized to give 11-chloro-6,6a,7,8,9,13b-hexahydro-7-methyl-12-methoxy-5H-benzo[d]naphth[2,1-b]azepine (9), a known precursor of 2. Several enantioselective syntheses, including a Jacobsen epoxidation route, a de novo synthesis from l-homophenylalanine, and a classical salt resolution sequence, were developed for the preparation of the key intermediates in chiral form.