Reactions of Acetoacetic Ester Blocked Cyclohexyl Isocyanate

Article abstract of DOI:10.1021/jo01300a036

Acetoacetic ester has been widely reported to be a blocking agent for isocyanates.However, we find that only a trace of isocyanate is formed by thermolysis of acetoacetic ester blocked cyclohexyl isocyanate, 1, at 150 deg C and atmospheric pressure.The major portion is unchanged even after 8 h, with some conversion to acetylmalonic ester, 2, and acetyl-N,N'-dicyclohexylmalonamide, 3.Alcoholysis does not yield the "normal" urethane as blocked isocyanates do but rather esters of 1 with some diesters of 2 and smaller amounts of 3.Significant amounts of N-cyclohexylacetamide, N-cyclohexylmalonamate ester, and some N,N'-dicyclohexylmalonamide are also obtained.Aminolysis leads to N-substituted acetamides and N-cyclohexylmalonamate but no substituted ureas, the "normal" products for aminolysis of blocked isocyanates.In the presence of acid catalysts, alcoholysis leads to N-cyclohexylmalonamates with acetate esters as the other product.