Synthesis of α-Cyano Carbonyl Compounds by Flash Vacuum Thermolysis of (Alkylamino)methylene Derivatives of Meldrum's Acid. Evidence for Facile 1,3-Shifts of Alkylamino and Alkylthio Groups in Imidoylketene Intermediates

Article abstract of DOI:10.1021/jo00003a014

The syntheses and flash vacuum thermolyses of 5-<(alkylamino)methylene>-2,2-dimethyl-1,3-dioxane-4,6-diones (Meldrum's acid derivatives) 13a - i are described.Thermolysis of 13a as well as of ethyl 3-(tert-butylamino)acrylate (22) gives a tautomeric mixture of cyanoacetaldehyde (14) and 3-hydroxypropenenitrile (15).Thermolysis of 13b gives iminoacrolein 26 and not cyanoacetone (29).Thermolysis of 13c, d gives S-methyl cyanothioacetate (30), and 13f - h give cyanoacetamides 31 in high yields. 2-Cyanopent-4-enoic acid derivatives 32 are obtained from Meldrum's acids 13e, i.The results are discussed in terms of facile 1,3-shifts of methylthio and alkylamino groups in imidoylketenes, interconverting imidoylketenes and acylketene imines.