Thiocarbamates from thiocyanates

S-Thiocarbamic acid esters from thiocyanates SCN —>- SCONH ... 

The reaction is carried out at low temperature in aqueous medium and then allowed to stand overnight (221). Ammonium thiocarbamate is prepared from a cold saturated solution of ammonium thiocyanate, which is gradually added to dilute sulfuric acid at 25°C. The liberated carbonyl sulfide is passed into a saturated solution of alcoholic ammonia at about 10°C (221). The fairly low yield indicates that the reaction has not been greatly developed. 

The reaction of 3-phenylpropenoyl iso thiocyanates (285) with sodium hydrogen sulfide in methanol gives thiazinones (286) and thiocarbamates (287) (Scheme 56). The thiocarbamates are derived from the thiazinones through methanolysis and can be recyclized to them by treatment with aqueous sodium hydroxide in a separate step <90MI 607-01 >. 

Starting from 1,2-0-sulfinyl-a-D-glycopyranose or glycofuranose. Treatment of the Q -l,2-0-sulfinyl derivative with sodium thiocyanate led to a p-thiocyanate that, imder the reaction conditions was isomerized to a transient a-isothiocyanate via an oxocarbenium ion. The isothiocyanate underwent spontaneous annelation with a vicinal hydroxyl group to afford the corresponding glycopyrano and glycofurano cis-fused thiocarbamates (Scheme 13). 

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