This
work continues our group’s research into the synthesis
and study of the catalytic activity of ruthenium chelates with various
heteroatoms (O, S, N, and Se) in a six-membered ring. It was found
that second-generation Hoveyda–Grubbs-type catalysts containing
a sulfur-ruthenium coordinate bond in a six-membered chelate ring
can be prepared easily and in high yields using standard procedures,
based on the interaction between (2-vinylbenzyl)sulfanes and Ind II (the common precursor for Ru-complex synthesis). The
obtained ruthenium derivatives, with a donor-acceptor S → Ru bond, can exist in two isomeric forms according to the
arrangement of substituents around the central metal atom. Kinetically
controlled trans-isomers are formed at temperatures
below 80 °C in heptane and are less thermodynamically stable
compared with cis-isomers, which arise under heating
of trans-S-chelates in 1,2-dichloroethane
at 110 °C. The structures of all the cis- and trans-isomers were determined and characterized in detail
by X-ray diffraction and nuclear magnetic resonance. The study of
the activity of the catalysts in standard ring-closing metathesis
and ring-opening metathesis polymerization reactions showed that the cis-isomers are inactive in the absence of thermal or UV
activation, while trans-complexes of the same type
display excellent catalytic properties at r.t. that are superior to
those of the commercially available HG-II catalyst. The structure,
spectral characteristics, and catalytic activity of the catalysts
containing an S → Ru bond in a six-membered
chelate ring were compared with their five-membered analogues obtained
in previous works.
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 N→Ru 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.
The title compound, C24H24N2O5S, crystallizes with two independent molecules (A and B) in the asymmetric unit. In the central ring systems of both molecules, the tetrahydrofuran rings adopt envelope conformations, the pyrrolidine rings adopt a twisted-envelope conformation and the six-membered ring is in a boat conformation. In molecules A and B, the nine-membered groups attached to the central ring system are essentially planar (r.m.s. deviations of 0.002 and 0.003 Å, respectively). They form dihedral angles of 64.97 (9) and 56.06 (10)°, respectively, with the phenyl rings. In the crystal, strong intermolecular O—H...O hydrogen bonds and weak intermolecular C—H...O contacts link the molecules, forming a three-dimensional network. In addition weak π–π stacking interactions [centroid-to centroid distance = 3.7124 (13) Å] between the pyrrolidine rings of the nine-membered groups of A molecules are observed. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to quantify the intermolecular interactions present in the crystal, indicating that the environments of the two molecules are very similar. The most important contributions for the crystal packing are from H...H (55.8% for molecule A and 53.5% for molecule B), O...H/H...O (24.5% for molecule A and 26.3% for molecule B) and C...H/H...C (12.6% for molecule A and 15.7% for molecule B) interactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.