Synthesis of 2,5-cyclohexadien-4-one-spiro-3 '-(2 '-R-5 ',5 '-dimethyl-1 '-pyrrolines) by the Ritter reaction

Reactions of 1-(4'-methoxyphenyl)-2-methylpropene with nitriles RCN in concentrated sulfuric acid give 2,5-cyclohexadien-4-one-spiro-3'-(2'-R-5',5'-dimethyl-1'-pyrrolines) in good yields.