Synthesis of 5,6,6a,7,7a,12a-hexahydro-4H-benzo[d,e]benzothieno-[2,3-g]quinolines and of 8-phenyl-2,3,7,8,9,9a-hexahydro-1H-benzo[d,e] quinolines

Abstract

Demethylation of 1-(3-benzo[b]thienylmethyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (1; R = H) gives two diastereoisomeric 1,2-dihydroxy-5,6,6a,7,7a,12a-hexahydro-4H-benzo[d,e]benzothieno-[2,3-g]quinolines (4; R = H). Desulphurisation of their N-acetyl-di-O-methyl derivative (5; R¹= Me, R²= Ac) gave the diastereoisomeric 1-acetyl-5,6-dimethoxy-8-phenyl-2,3,7,8,9,9a-hexahydro-1H-benzo[d,e]quinolines (6; R = Ac). Desulphurisation of 6-formyl-1,2-dimethoxy-5,6,6a,7,7a,12a-hexahydro-4H-benzo[d,e]benzothieno[2,3-g]quinoline (5; R¹= Me, R²= CHO) gave 1-formyl-5,6-dimethoxy-8-phenyl-2,3,9,9a-tetrahydro-1H-benzo[d,e]quinoline (7; R = CHO) together with two separable diastereoisomers of the corresponding hexahydro-derivative (6; R = CHO); all of these were converted into the corresponding N-methyl derivatives (7; R = Me) and (6; R = Me) respectively. Evidence for these structures has been provided by alternative synthesis. A novel process for monophenylation of alkyl aryl ketones is described.