Low-Temperature Chemo- and Stereoselective [2+2]-Cyclodimerization of 5-Ethenylidene-4,5-dihydro-1,3-thiazole: An Approach to Unique Derivatives of 1,3-Bis(methylene)cyclobutane

An unusual [2+2]-cyclodimerization of 5-ethenylidene-4,5-dihydro-1,3-thiazole, obtained from lithiated methoxyallene, isopropyl isothiocyanate, and propargylbromide, into highly functionalized 1,3-bis(methylene)cyclobutane is discovered.