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Synthesis of trans/cis 4-substituted 3-furyl-2-phenethyltetrahydroisoquinolin-1-ones: conformation of the trans-4-(pyrrolidinylcarbonyl) derivative |
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| Authors: | Malinka P Stoyanova Krasimir S Kosev Venelin G Enchev |
| Institution: | a Sofia University, Faculty of Chemistry, 1 J. Bouchier Avenue, 1164 Sofia, Bulgaria b Bulgarian Academy of Sciences, Institute of Organic Chemistry, Acad. G. Bontchev Street, bl.9, 1113 Sofia, Bulgaria c Bulgarian Academy of Sciences, Central Laboratory of Mineralogy and Crystallography, Acad. G. Bontchev Street, bl.107, 1113 Sofia, Bulgaria |
| Abstract: | The title compounds were synthesized starting from homophthalic anhydride and an imine. The amides obtained showed unexpected values for 3J3,4 that cannot be used to deduce their configuration and conformation. This problem was resolved for one representative compound (the 4-(pyrrolidinylcarbonyl) derivative) by means of detailed NMR studies, X-ray diffraction and theoretical calculations. The compound has the trans configuration. In the solid state, its conformation is with dipseudoaxial (aa) oriented substituents at positions 3 and 4. In different solvents and in the gas-phase, the majority of the data reveal that the observed value of 3J3,4 results from an equilibrium of the ee and aa conformers. |
| Keywords: | trans- and cis-Tetrahydroisoquinoline Carboxamides Conformational equilibrium Ab initio and DFT calculations Crystal structure Dynamic NMR |
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