Expedient Access to 2,3-Dihydropyridines from Unsaturated Oximes by Rh(III)-Catalyzed C–H Activation
摘要:
alpha,beta-Unsaturated - oxime pivalates are proposed to undergo reversible C(sp(2))-H insertion with cationic Rh (III) complexes to furnish five-membered metallacycles. In the presence of 1,1-disubstituted olefins, these species participate in irreversible migratory insertion to give, after reductive elimination, 2,3-dihydropyridine products in good yields. Catalytic hydrogenation can then be used to. convert these molecules into piperidines, which are important structural components of numerous pharmaceuticals.
A titanocene-mediated intramolecular radical addition of different epoxy vinyl- and allylsulfones has been achieved. Five- and Six-membered ring products were obtained in good to excellent yields in the presence of both 2.2 and 0.2 equiv of Cp2TiCl. A novel double-activation strategy allowed us to achieve small-size rings such as cyclobutanes and cyclopropanes.
Cauquis,G.; Haemmerle,B., Bulletin de la Societe Chimique de France, 1970, p. 190 - 192