Direct N–H/α,α,β,β-C(sp<sup>3</sup>)–H functionalization of piperidine<i>via</i>an azomethine ylide route: synthesis of spirooxindoles bearing 3-substituted oxindoles
A protocol for the direct functionalization of N-H/[small alpha],[small alpha],[small beta],[small beta]-C(sp3)-H of piperidine without any metal or external oxidants is reported. These reactions are promoted by 4-(trifluoromethyl)benzoic acid via an azomethine ylide intermediate....
Catalytic Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides with Vinyl Sulfones
作者:Tomás Llamas、Ramón Gómez Arrayás、Juan C. Carretero
DOI:10.1021/ol060314c
日期:2006.4.1
see text] A general protocol for the enantioselective catalytic 1,3-dipolarcycloaddition of azomethine ylides with aryl vinyl sulfones is described. Nearly complete exo selectivity and enantioselectivities up to 85% ee are attained with Cu(CH(3)CN)(4)ClO(4)/Taniaphos as the catalyst system. The resulting enantioenriched 3-sulfonyl cycloadducts are versatile intermediates in the synthesis of 2,5-disubstituted
Selective coordination of a chiralLewisacid to an enantiotopic sulfonyl oxygen enabled enantioselective allylation of the α-sulfonyl radical. The addition–allylation products were obtained in low to good stereoselectivities (up to 84% ee).