N-thio- and N-selenophenacylamidines: electrophilic activation as a route to some 1-hetero-3-aza-4-dimethylaminobuta-1,3-dienes

The preparation of 2-phenyl-4-dimethylamino-1-aza-, 1-oxa-, 1-thia-, 1-sele na-3-azabuta-1,3-dienes as well as their 4-methyl derivatives is described following a new heteroatom interchange reaction process. Heteronucleophilic attack at one particular reactive site of bis-electrophilic amidinium salt s is the key feature of the process. In addition, we also disclose that the substituted 1-oxa-3-aza- and 1,3-diazabuta-1,3-dienes can be obtained by a reactional transformation cascade initiated by either silver acetate addit ion or tosyl azide [3+2] cycloaddition onto the CS or CSe double bonds of t he 1-thia- and 1-selena-3-azabuta-1,3-diene analogues.