A Simple and Efficient Synthesis of New Dihydrospiro[(1H)Quinoline‐2,1′‐Cyclohexane] Derivatives Via Internal Friedel‐Crafts Alkene Alkylation of N‐(1‐Allylcyclohexanyl)Ethylphenylamine

Abstract

New substituted dihydrospiro[(1H)quinoline‐2,1′‐cyclohexanes] were prepared by the internal alkene alkylation of N‐(1‐allylcyclohexanyl) ethylphenylamine obtained from the corresponding ketimine and allylmagnesium bromide. The 1‐allyl‐6‐ethyl‐4‐methyl‐3,4‐dihydrospiro[(1H)quinoline‐2,1′‐cyclohexane] undergoes an amino‐Claisen transposition (BF₃ · Et₂O) to afford the 8‐allyl‐6‐ethyl‐4‐methyl substituted spiroquinolines or a second internal alkylation reaction promoted by Brönsted acid (H₂SO₄) to give a new unnatural lilolidine spiroderivative.

Keywords:

• Internal alkene Friedel‐Crafts alkylation
• amino‐Claisen transposition
• spiroquinolines

Acknowledgments

This work was supported by the grant of the Colombian Institute for Science and Research (COLCIENCIAS, projects: 1102‐05‐11429). Thanks are also due to Dr. F. Zubkov (Organic Chemistry Department of the Russian Peoples Friendship University) for providing ¹H NMR spectra.