Catalytic Asymmetric C–H Insertions of Rhodium(II) Azavinyl Carbenes
摘要:
A highly efficient enantioselective C-H insertion of azavinyl carbenes into unactivated alkanes has been developed. These transition metal carbenes are directly generated from readily available and stable 1-sulfonyl-1,2,3-triazoles in the presence of chiral Rh(II) carboxylates and are used for C-H functionalization of alkanes to access a variety of beta-chiral sulfonamides.
with exclusive regioselectivity and stereoselectivity. Functional application of such a resultant product by oxidative addition and epoxidation is also explored. Notably, the treatment of a pyrroline-fused N-glycoside (3a) with TMSOTf efficiently leads to an interesting unexpected C-nucleoside (9) via a TMSOTf-inducing ring opening/acetyl migration/ringclosingreaction sequence.
Cu2O acting as a robust catalyst in CuAAC reactions: water is the required medium
作者:Kai Wang、Xihe Bi、Shuangxi Xing、Peiqiu Liao、Zhongxue Fang、Xianyu Meng、Qian Zhang、Qun Liu、Yu Ji
DOI:10.1039/c0gc00848f
日期:——
Cu2O as the catalyst in water was found to be quite robust for the azide-alkyne cycloaddition (AAC) reaction, which was verified by a wide variety of applicable azides and alkynes. Water was proved to play an essential role because of a significant rate acceleration compared with reactions using organic solvents and conducted under neat conditions. The high catalytic performance of Cu2O/H2O system was further argued by decreasing the catalyst loading to ppm levels.
Tandem O–H Insertion/[1,3]-Alkyl Shift of Rhodium Azavinyl Carbenoids with Benzylic Alcohols: A Route To Convert C–OH Bonds into C–C Bonds
作者:Pengbing Mi、Rapolu Kiran Kumar、Peiqiu Liao、Xihe Bi
DOI:10.1021/acs.orglett.6b02459
日期:2016.10.7
Alcohols are among the most abundant and commonly used organic feedstock in industrial processes and academic research. The first tandem O–H insertion/[1,3]-alkyl shift reaction reported is between benzylicalcohols and rhodium azavinyl carbenoids derived from N-sulfonyl-1,2,3-triazoles, which provides a strategically novel way of cleaving C–OH bonds and forming C–C bonds. The substrate scope is broad
various functionalized enamides. The developed reaction involves the unprecedented [2,3]-sigmatropic rearrangement of sulfur ylides with the imine motif. Importantly, the method works well with various substituted α-thioesters/-amides/-ketones and substituted N-sulfonyl-1,2,3-triazoles and allows the synthesis of diverse enamide derivatives in good to excellent yields. The reaction was also successfully