Preparation of 2,3-dihydrothiazolo[2,3-a]isoquinolinium salts and their reactions with complex metal hydrides

Abstract

3-Methyl-2,3-dihydrothiazolo[2,3-a]isoquinolinium perchlorate (3; R = Me) has been synthesised by the cyclisations of 1-allylthioisoquinoline (1) and β-hydroxypropylthioisoquinoline (4; X = H, OH; R = Me). 2,3-Dihydrothiazolo[2,3-a]isoquinolinium perchlorate (3; R = H) was obtained from β-hydroxyethylthioiso-quinoline (4; X = H, OH; R = H) as well as 1-mercaptoisoquinoline and ethylene dibromide. Reduction of 3-methyl-2,3-dihydrothioazolo[2,3-a]isoquinolinium perchlorate (3; R = Me) and 3-methylthiazolo[2,3-a]isoquinolinium perchlorate (10; R = Me) with LAH or NaBH₄ gave 3-methyl-2,3-dihydro-10bH-thiazolo[2,3-a]isoquinoline (7), 3-methyl-2,3,5,6-tetrahydro-10bH-thiazolo[2,3-a]isoquinoline (8) and a minor component of undetermined structure. 3-Bromomethyl-2,3-dihydrothiazolo[2,3-a]isoquinolinium perchiorate (12) obtained from (1) and bromine was hydrogenolysed with LAH to (7) and (8).