Synthesis of Mixed Acyloins. IV

Structural Effects of Aromatic Rings on a Reaction of Methylmagnesium Iodide towards Aromatic Aldehyde Cyanohydrins

Abstract

The three isomers of bromomandelonitrile, by reaction with methylmagnesium iodide, form corresponding bromophenylacetylcarbinol (I) as well as bromophenyl-methylcarbinol (II). Of these, report has already been made on the para-isomer. In the present series of experiments, the ortho-isomer of (I), b.p₅ 127-131° (semicarbazone, m. p. 181°), and of (II), b.p₅ 115-120° (phenylurethan, m. p. 78-79°), were obtained in 36.3% and 15.8% yield, and the meta-isomer of (I), b.p₆ 143-145° (semicarbazone, m. p. 194.5°), and of (II), b.p₆ 125-131°, were obtained in 31.5% and 20.8% yield respectively. As a result of comparing the reaction of mandelonitrile and methoxymandelonitrile with methylmagnesium iodide, it is seen that the bromine in the aromatic ring of the cyanohydrin, used as the starting material, affects this kind of reactions favorably for the fomation of (I) and unfavorably for the formation of (II). Approximately similar results were obtained in the reaction of furfural- and 2-thiophenaldehyde cyanohydrin with methylmagnesium iodide.