The reactions of 1-(p-methoxyphenyl)-2-methylpropan-1-ol or alpha-cyclohexyl-p-methoxy-benzyl alcohol with nitriles RCN in concentrated sulfuric acid afforded 1-R-3,3-dialkyl-2-azaspiro[4.5]deca-1,6,9-trien-8-ones. The stability of the latter toward the dienone-phenolic rearrangement depends on the nature of the substituent R. The reaction mechanism was studied by the semiempirical quantum-chemical AM1 method.