thiourea in ethanol

in tetrahydrofuran large excess of HC3N mixt. stirred (ca. 40 h, room temp.); solvent removed (vac.), residue extd. (CH2Cl2), filtered (Celite), concd., chromd. (silica gel, CH2Cl2/hexane 2:1), eluted (CH2Cl2), concd., recrystd. ((CH2Cl2/hexane); elem. anal.;

in dichloromethane 1:1 mixt. stirred (-20°C, ca. 4 h); solvent removed (vac.), residue extd. (CH2Cl2), filtered (Celite), concd., chromd. (silica gel, CH2Cl2/hexane 2:1), (1. fraction = product 2), eluted (CH2Cl2), concd., recrystd. ((CH2Cl2/hexane); elem. anal.;