Abnormal addition of free radicals to sterically hindered nitrosobenzenes

Abstract

1-Cyano-1-methyl- and 1-methoxycarbonyl-1-methyl-ethyl radicals reacted with 2,4,6-tri-t-butylnitrosobenzene (I) to give abnormal 1,6-addition products, 1-(1-cyano-1-methylethoxyimino)-4-(1-cyano-1-methylethyl)-2,4,6-tri-t-butylcyclohexa-2,5-diene (III) and the corresponding methoxycarbonyl derivative (IV), respectively. We suggest that the reactions proceed via anilino-radicals (II) formed by attack of the radical on the nitroso-oxygen atom. The reaction of 2-methyl-4,6-di-t-butylnitrosobenzene (VI) with the 1-cyano-1-methylethyl radical afforded N-isopropylidene-2-methyl-4,6-di-t-butylaniline N-oxide (VII) and 3-(1-cyano-1-methylethyl)-5,7-di-t-butyl-2,1-benzisoxazole (VIII). 2,5-Di-t-butylnitrosobenzene reacted with 1-cyano-1-methylethyl radicals to produce a normal addition product (XI).