Nitrone/Imine Selectivity Switch in Base-Catalysed Reaction of Aryl Acetic Acid Esters with Nitrosoarenes: Joint Experimental and Computational Study

Herein we report a mild and diastereoselective access to ketonitrones by reacting easily available aryl acetic acid esters and other active methylene compounds, with nitrosoarenes under catalytic loading of 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) at room temperature. Depending on the substitution pattern and nature of the aryl moiety, a switch toward the formation of imines can be observed. The mechanistic framework is put to scrutiny by experimental and theoretical studies, pointing to the formation of a nitroso aldol intermediate, whose fate toward one of the competing pathways, namely hydride transfer or elimination, would depend upon the NOH/CHα relative acidities. (Figure presented.).