Promotion of the Nitroaldol Henry Reaction

Bases lb. Id, and 9b catalyze the nitroaldol reaction with ketones and aldehydes at room temperature in the presence of MgS04 in generally superior yields [Eq. (14)] [123]. Moreover, ketone self-condensation was not problematic under our conditions. In a comparison of the effectiveness of Id with le and If in these reactions, le and If were more efficacious [71]. 

The title compounds are useful intermediates in organic synthesis as, for example, for making 1,3-amino alcohols [124]. -Hydroxy nitriles can be made by a variety of methods, most of which suffer one or more of the following disadvantages poor to moderate yields, toxicity of a catalyst or solvent, fire or explosion hazard, lengthy reactions times, multistep syntheses and low temperatures. 

Pro-azaphosphatranes lb. Id, and 9b catalyze the reaction of aldehydes with acetonitrile to give the title compounds in very good to excellent yields [124]. In a comparison of the efficacy of le with Id in several cases, le was more effective but If was quite inactive [71]. Aldehydes taking part in this reaction form secondary alcohols which are less sterically hindered and can be more easily depro-tonated, thus leading to a,jS-unsaturated nitriles. Primary aldehydes, however, undergo aldol condensation. 

Contrary to our observation with 9b, lb does not produce substantial quantities of the corresponding undesired a, -unsaturated nitrile and gives higher 

An indirect approach to a, -unsaturated nitriles involves the condensation of a carbonyl compound with acetonitrile using strong ionic bases such as -BuLi, giving the /i-hydroxy nitrile, which is then isolated and thermally dehydrated in the presence of a strong add. The aforementioned strategies, in addition to several others that could be mentioned [125], are less convenient and less versatile (for reasons mentioned in connection with the classical methods) than the one we now describe. 

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