RESUMO
The ring rearrangement metathesis (RRM) of a trans-cis diastereomer mixture of methyl 3-allyl-3a,6-epoxyisoindole-7-carboxylates derived from cheap, accessible and renewable furan-based precursors in the presence of a new class of Hoveyda-Grubbs-type catalysts, comprising an NâRu coordinate bond in a six-membered ring, results in the difficult-to-obtain natural product-like cyclopenta[b]furo[2,3-c]pyrroles. In this process, only one diastereomer with a trans-arrangement of the 3-allyl fragment relative to the 3a,6-epoxy bridge enters into the rearrangement, while the cis-isomers polymerize almost completely under the same conditions. The tested catalysts are active in the temperature range from 60 to 120 °C at a concentration of 0.5 mol % and provide better yields of the target tricycles compared to the most popular commercially available second-generation Hoveyda-Grubbs catalyst. The diastereoselectivity of the intramolecular Diels-Alder reaction furan (IMDAF) reaction between starting 1-(furan-2-yl)but-3-en-1-amines and maleic anhydride, leading to 3a,6-epoxyisoindole-7-carboxylates, was studied as well.
Assuntos
Produtos Biológicos/síntese química , Pirróis/química , Rutênio/química , Produtos Biológicos/química , Catálise , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Conformação Molecular , Solventes/química , Estereoisomerismo , TemperaturaRESUMO
The title compound, C24H24N2O5S, crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. In the central ring systems of both mol-ecules, the tetra-hydro-furan rings adopt envelope conformations, the pyrrolidine rings adopt a twisted-envelope conformation and the six-membered ring is in a boat conformation. In mol-ecules A and B, the nine-membered groups attached to the central ring system are essentially planar (r.m.s. deviations of 0.002 and 0.003â Å, respectively). They form dihedral angles of 64.97â (9) and 56.06â (10)°, respectively, with the phenyl rings. In the crystal, strong inter-molecular O-Hâ¯O hydrogen bonds and weak inter-molecular C-Hâ¯O contacts link the mol-ecules, forming a three-dimensional network. In addition weak π-π stacking inter-actions [centroid-to centroid distance = 3.7124â (13)â Å] between the pyrrolidine rings of the nine-membered groups of A mol-ecules are observed. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to qu-antify the inter-molecular inter-actions present in the crystal, indicating that the environments of the two mol-ecules are very similar. The most important contributions for the crystal packing are from Hâ¯H (55.8% for mol-ecule A and 53.5% for mol-ecule B), Oâ¯H/Hâ¯O (24.5% for mol-ecule A and 26.3% for mol-ecule B) and Câ¯H/Hâ¯C (12.6% for mol-ecule A and 15.7% for mol-ecule B) inter-actions.