Unexpected Isolation of 4‐Isothiocyanatomethylene‐4H‐pyridine‐1‐carboxylic Acid Ethyl Ester as Potential Template in Organic Synthesis

Abstract

The synthesis of 4-isothiocyanatomethyl-pyridine 4 in 36% yield by Hasegawa and Kotani (Japanese patent 49088878, 1974) has spurred us to investigate this preparation in detail. In addition to this compound, 4-isothiocyanatomethylene-4H-pyridine-1-carboxylic acid ethyl ester 3 can be isolated. The synthesis of both compounds 3 and 4 were optimized to 75% and 50% yield respectively. Reaction of compound 3 with methylamine gave thiourea derivatives 5, the same product obtained on reacting 4-isothiocyanatomethyl-pyridine 4 with methylamine. We succeed in adjusting the reaction conditions to obtain high yield either from compound 3 or isothiocyanate derivatives 4.