(S)-3-Hydroxymethyl-N-(pyrid-3-yl)-1,2,3,4-tetrahydroisoquinoline-2-carbothioamide → 1,5,10,10a-Tetrahydrothiazolo[3,4-b]isoquinoline

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Reaction Steps

(S)-3-Hydroxymethyl-N-(pyrid-3-yl)-1,2,3,4-tetrahydroisoquinoline-2-carbothioamide (13.5 g.) in 6N hydrochloric acid (300 cc.) is heated for 40 minutes at 100° C. After cooling, the solution obtained is concentrated under reduced pressure (25 mm. Hg) to 1/5 of its volume. It is rendered alkaline by adding 10N sodium hydroxide solution (200 cc.) and is then extracted with methylene chloride (3 × 150 cc.). The organic extracts are combined and then dried over magnesium sulphate. After filtering, and concentrating the filtrate to dryness under reduced pressure (25 mm. Hg), a yellow oil (11 g.) is obtained, which crystallises on addition of diisopropyl ether (150 cc.). The white crystals are filtered off, washed with diisopropyl ether (3 × 10 cc.) and then dried at 60° C., under reduced pressure (1 mm. Hg). (S)-3-Pyrid-3-ylimino)-1,5,10,10a-tetrahydrothiazolo[3,4-b]isoquinoline (9.8 g.), melting at 111° C., is thus obtained.

Provenance & Evidence