Higher cycloalkanone(s) prepn. - from homologous cpds. of lower mol. wt., via cyclo:alkylidene-cyano-acetate intermediates

摘要

Prepn. of cycloalknones (I) contg. n+1 ring C atoms from cycloalkanones (II) contg. n ring C atoms comprises subjecting (II) to Knoevenagel condensation with a cyanoacetate ester to form a cycloalkylidene-cyanoacetate ester (III) contg. n ring C atoms. (III) is then converted to the corresp. pyrazoline by addn. of diazomethane at -20 degrees C, and the product is subjected to thermolysis in boiling CHCl3 to form a cycloalkylidene-cyanoacetate ester (IV) contg. n+1 ring C atoms. Cpd. (IV) is then converted to (I) by hydrolysis (when n+1 is not = 10) or by permanganate oxidn. (when n+1=10). Process is esp. useful for preparing >=8C cycloalkanones for use in perfumery. Higher yields (e.g. 35-73%) are obtd. than by simple diazomethan addn. and the formation of mixts. of different cycloalkanones, is avoided.