RING-CHAIN TAUTOMERISM IN THE PRODUCTS OF THE REACTION BETWEEN 5-SUBSTITUTED FURFURYLAMINES AND ANHYDRIDES OF α,β-UNSATURATED CARBOXYLIC ACIDS
DOI:
https://doi.org/10.1007/2818Keywords:
furan, isoindole, [4 2] cycloaddition, dynamic stereochemistry, intramolecular Diels–Alder reaction, ring-chain tautomerismAbstract
The reactions of 5-substituted furfurylamines with anhydrides of α,β-unsaturated carboxylic acids (acryloyl chloride and maleic anhydride) were studied. The first step of the reaction mechanism involved acylation of furfurylamine nitrogen atom, followed by a stereospecific, spontaneous intramolecular Diels–Alder reaction at the furan ring of the N-furfurylamide intermediates. When the starting materials were 5-alkyl-substituted furfurylamines, the expected 1-oxo-2,3,7,7a-hexahydro-1Н-3а,6-epoxyisoindoles or the corresponding 7carboxylic acids were obtained in up to 98% yields. The acylation of 5-aryl-substituted furfurylamines with maleic anhydride led to N-furfurylmaleic amides, which formed a dynamic equilibrium in solutions with adducts formed by intramolecular [4+2] cycloaddition, 3а,6-epoxyisoindole-7-carboxylic acids, as proved by NMR spectroscopy. X-ray structural analysis results show that these mixtures crystallized in the form of the cyclic tautomer.
Authors: Fedor I. Zubkov*, Victor D. Golubev, Vladimir P. Zaytsev, Olga V. Bakhanovich, Evgeniya V. Nikitina, Victor N. Khrustalev, Rinat R. Aysin, Tatiana V. Timofeeva, Roman A. Novikov, Aleksey V. Varlamov