Novel stereoselective syntheses of the fused benzazepine dopamine D1 antagonist (6aS,13bR)-11-chloro-6,6a,7,8,9,13b-hexahydro-7-methy-5H-benzo[d]naphth[2,1-b]azepin-12-ol (Sch 39166):: 1.: Aziridinium salt based syntheses

Several novel enantioselective syntheses of the dopamine D-1 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-]H-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 transamine 1-(4-chloro-3-methoxyphenyl)-N-(2,2-dimethoxyethyl)-1,2,3,4 -tetrahydro-N-methyl-2-naphth-alenamine (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.