Rhodium-Catalyzed Oxidative Synthesis of Quinoline-Fused Sydnones via 2-fold C–H Bond Activation
作者:Lei Li、He Wang、Xifa Yang、Lingheng Kong、Fen Wang、Xingwei Li
DOI:10.1021/acs.joc.6b02356
日期:2016.12.2
Rh(III)-catalyzed synthesis of mesoionic heterocycles has been achieved via C–H activation of sydnones and oxidative coupling with internal alkynes. This reaction occurred under mild conditions with high efficiency, broad substrate scope, and low catalyst loading. Moreover, synthetic applications of a coupled product have been demonstrated in the late-stage derivatization into a variety of highly functionalized
of 4-trifluoromethyl pyrazoles have been prepared via the copper-catalyzed cycloaddition of 2-bromo-3,3,3-trifluoropropene with a variety of N-arylsydnone derivatives under mild conditions. This new protocol under optimized reaction conditions [Cu(OTf)2/phen, DBU, CH3CN, 35 °C] afforded 4-trifluoromethyl pyrazoles in moderate to excellent yields with excellent regioselectivity.
and general method for the synthesis of 3-trifluoromethyl-4‑trifluoroacetyl pyrazoles from the cycloaddition of sydnones with 1,1,1,5,5,5-hexafluoropentane-2,4-dione has been established. Using ZnI2/bpy as a catalyst in THF, this protocol proved to be general to prepare a variety of 3-trifluoromethyl-4‑trifluoroacetyl pyrazoles in good yields. Utility of this method was demonstrated by further transformations
A general and regioselective synthesis of 3-trifluoromethyl 1,2,4-triazoles has been achieved through photocycloaddition of sydnone with trifluoroacetonitrile. This method employed trifluoroacetaldehyde O-(aryl)oxime as the CF3CN precursor and tolerated various functional groups to furnish 3-trifluoromethyl 1,2,4-triazole products in moderate to good yields. Mechanistic experiments revealed an energy