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
A novel and efficient approach to the synthesis of 2-vinylbenzylamines is reported. This involves obtaining 2-vinylbenzylamine ligands from tetrahydroisoquinoline by alkylation and reduction followed by the Hofmann cleavage. The resultant 2-vinylbenzylamines allowed us to obtain new Hoveyda-Grubbs catalysts, which were thoroughly characterised by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10-2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM).
RESUMO
The title compound, [RuCl2(C21H26N2)(C11H15N)], is an example of a new generation of N,N-dialkyl metallocomplex ruthenium catalysts with an NâRu coordination bond as part of a six-membered chelate ring. The Ru atom has an Addison τ parameter of 0.234, which indicates a geometry inter-mediate between square-based pyramidal and trigonal-bipyramidal. The complex shows the usual trans arrangement of the two chloride ligands, with Ru-Cl bond lengths of 2.3397â (8) and 2.3476â (8)â Å, and a Cl-Ru- Cl angle of 157.47â (3)°. The crystal structure features C-Hâ¯Cl, C-Hâ¯π and π-π stacking inter-actions. The solvent mol-ecules were found to be highly disordered and their contribution to the scattering was removed with the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71, 9-18], which indicated a solvent cavity of volume 1096â Å3 containing approximately 419 electrons. These solvent mol-ecules are not considered in the given chemical formula and other crystal data.