Reactions of Thioamides and Selenoamides with Hydrazonoyl Chlorides Under Phase-Transfer Conditions. A Convenient Method of Preparation of δ²-1,3,4-Thiadiazolines and δ²-1,3,4-Selenadiazolines

Abstract

Reactions of enolizable thio- and selenoamides with hydrazonoyl chlorides in the presence of bases and phase-transfer catalysts result in 2-dialkylamino-Δ²-1,3,4-thia- and selenadiazolines. The reactions proceed through formation of corresponding enethiolates and eneselenolates. At 80°C 2-dialkylamino-Δ²-1,3,4-thia- and selenadiazolines eliminate dialkylamines, giving 2-ylidene-Δ²-1,3,4-thia- and selenadiazolines in good yield. The reaction of non-enolizable thioamides with hydrazonoyl chlorides in the presence of bases and phase-transfer catalyst occurs as 1,3-dipolar cycloaddition of nitrilimines derived from hydrazonoyl chlorides to the C=S bond, yielding Δ²-1,3,4-thiadiazolines.

Keywords::

• Thioamide; selenoamide
• thiadiazoline
• selenadiazoline
• phase-transfer catalysis
• hydrazonoyl chloride