facile conversion of aldehydes into nitriles via the sulphonyl hydrazones

ABSTRACT

Although many reagents are available to affect the conversion of aldehydes to nitriles, the majority is electrophilic in character, or require acidic conditions. Recently, thermal d composition [Scheme 1] of aldehyde derivatives in a concerted way offers an alternative for this conversion, in cases where thermal liability or inviolability does not offer an additional obstacle. In the second reaction [B], reactions due to radical fragmentation were the main reasons for the decreased yield of nitriles, since these produce in addition ozines and consequently ethylene. In order to drive the reaction completely towards the concerted pathway, we investigated the thermal fragmentation of N[1] benzoylphenylhydrazones, where steric factors may give the correct orientation for the transition state required for the concerted pathway and that leading to the exclusive formation of nitriles and benzanilide [Scheme2] In this case, we found that the pyrrolysis of the hydrazones Ia-f yields as anticipated mainly the desired nitrile III and benzanilide, however the pyrrolysis occurred only above 260 degree [230 - 320degree] and the yields of the nitriles range from 50-70 percent