Studies on isocyanides and related compounds. – Synthesis and cyclization of N‐substituted 1‐isocyano‐1‐cycloalkanecarboxamides

The Ugi four‐component condensation between cycloalkanones, isocyanides, and ammonium formate affords N ‐substituted 1‐formylamino‐1‐cycloalkanecarboxamides 1 which are dehydrated to give the corresponding isocyanides 2 . Compounds 2 are cyclized with arylsulfenyl thiocyanates to 1,3‐diazaspiro‐2‐thiones 4 and 5 . A series of 1,3‐diazaspiro[4,5]dec‐1‐en‐4‐ones 7 is prepared by cyclizing 2c–j with butyllithium. The structures of these compounds are confirmed by means of IR, 1 H‐NMR, and X‐ray analysis.