Enamines of 3,3-Dimethylazetidine

Article abstract of DOI:10.1021/jo00337a016

In an improvement over previous procedures, 3,3-dimethylazetidine (3) has been synthesized in 26percent yield from ethyl cyanoacetate.Rates of formation for the enamines of 3 and of pyrrolidine with 2-methylcyclohexanone (1) and 1-tetralone (2) have been studied.The 5- to 10-fold rate increase observed for 3 is attributed to diminished steric hindrance relative to pyrrolidine.Compared to the enamines of pyrrolidine with 1 and 2, those of 3 methylate initially on nitrogen to ggreater degree and are less selective for monomethylation.The enamine formed between 1 and 3 exists at equilibrium as an 83.17 mixture of tri- and tetrasubstituted isomers, in which the less substituted isomer has its vinyl H 1H NMR peak at δ 4.10.These properties are compared to those of other enamines of 1, in which a predictive relationship had previously been suggested.