A three-component coupling protocol for the synthesis of substituted hexahydropyrrolo[3,2-c]quinolines

Abstract

One pot reaction of anilines, benzaldehydes and 2-pyrrolines under lanthanide triflate catalysis affords substituted hexahydropyrrolo[3,2-c]quinolines in good to excellent yields.

References

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12. The ¹H NMR spectra of the endo and exo products are easily distinguished, and correlate well along the series 6a-i. The endo and exo stereochemistry was determined unambiguously by crystal structure determinations of 6f-endo and 6g-exo. Crystal data for 6f-endo: C₂₇H₂₆N₂O₄, M= 442.50, orthorhombic, P2₁2₁2, a= 11.0687(14), b= 25.113(3), c= 7.8901(8)Å, V= 2193.2(5)ų, Z= 4, T= 173(2) K, D_c= 1.340 Mg m^–3, µ= 0.090 mm^–1, 3622 reflections collected, 3622 independent reflections, R1 = 0.0426, R2 = 0.1042. For 6g-exo: C₂₅H₁₉Cl₅N₂O₂, M= 556.67, monoclinic, P2₁/c, a= 12.4852(8), b= 20.673(2), c+ 19.5393(14)Å, β= 105.48(2)°, V= 4860.4(6)ų, Z= 8, T= 293(2) K, D_c= 1.521 Mg m^–3, µ= 0.624 mm^–1, 21842 reflections collected, 6312 independent reflections, R1 = 0.0528, wR2 = 0.1333. CCDC 182/1171.
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14. Attempted three-component coupling of simple aliphatic aldehydes such as pentanal with 5 and an aniline does not result in the formation of aldehyde derived adducts, but instead leads to the formation of 7..