1-R-3,3-Dimethylbenzo[i]-2-azaspiro[4.5]deca-1,6-dien-8-ones or 1-R-3,3-dimethylbenzo[i]-2-azaspiro[4.5]deca-1,7-dien-6-ones were synthesized by three-component condensation of 1- or 2-methoxynaphthalene, isobutyraldehyde (or isobutylene oxide), and nitrile RCN in concentrated sulfuric acid.