A new route to optically pure tricarbonyl-chromium complexed ortho-substituted acetophenones

A new route to 2,5-dimethylacetophenone-tricarbonyl-chromium is devised, starting from the corresponding complex of 1-(2,5-dimethylphenyl)ethylamine. The process consists in synthesis of an azomethine complex followed by its regioselective alkylation via an aza-allylic carbanion. The hydrolysis of the new alkylated and isomerized azomethine affords the desired 2,5-dimethylacetophenone complex. Since the synthesis of the optically pure starling material has been previously accomplished, the present method provides a simple route to optically active chiral acetophenone complexes.