Synthesis of Substituted Tetrahydrochromenes by the Reactions of α,β-Unsaturated Cyanoesters with Dimedone/1,3-Cyclohexanedione

Abstract

Ethyl esters of 2-cyano-3-arylacrylic acid 1a–d (a = 4-CH₃-C₆H₄-, b = 4-N(CH₃)₂-C₆H₄-, c = 2-CH₃O-C₆H₄-, d = 2-Cl-C₆H₄-) reacted with 5,5-dimethyl-1,3-cyclohexanedione (2p, Y=CH₃), and 1e–g (e = 4-CH₃-C₆H₄-, f = 2-CH₃O-C₆H₄-, g = 2-Cl-C₆H₄-) reacted with 1,3-cyclohexanedione (2q, Y=H) in the presence of alcoholic sodium ethoxide to give the corresponding ethyl esters of 2-amino-7,7-dimethyl-5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromene-3-carboxylic acid 4a–d and 2-amino-5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromene-3-carboxylic acid 4e–g. The structures of the compounds 4a–g were confirmed by their ultraviolet, infrared, ¹H NMR, ¹³C NMR, and mass spectral data and elemental analyses.

Keywords:

• 4H-Chromene
• 1,3-cyclohexanedione
• 5,5-dimethyl-1,3-cyclohexanedione
• α,β-unsaturated cyanoesters

ACKNOWLEDGMENT

We are pleased to acknowledge Teruo Shinmyozu, Institute for Materials Chemistry and Engineering, Kyushu University, Japan, for the mass spectrum, NMR, and elemental analyses.