Unsymmetrical 1,1-diborated multisubstituted sp<sup>3</sup>-carbons formed via a metal-free concerted-asynchronous mechanism
作者:Ana B. Cuenca、Jessica Cid、Diego García-López、Jorge J. Carbó、Elena Fernández
DOI:10.1039/c5ob01523e
日期:——
unsymmetrical 1,1-diboration of diazo compounds, formed in situ from aldehydes and cyclic and non-cyclic ketones, in the absence of any transition metal complex. The heterolytic cleavage of the mixed diboron reagent, Bpin–Bdan, and the formation of two geminal C–Bpin and C–Bdan bonds has been rationalised based on DFT calculations to occur via a concerted-asynchronous mechanism. Diastereoselection is attained
I<sub>2</sub>-TBHP-catalyzed one-pot highly efficient synthesis of 4,3-fused 1,2,4-triazoles from N-tosylhydrazones and aromatic N-heterocycles via intermolecular formal 1,3-dipolar cycloaddition
I2-TBHP-catalyzed azomethine imine generation and subsequent regioselective 1,3-dipolarcycloaddition (DC) with aromatic N-heterocycles was developed to afford various 4,3-fused 1,2,4-triazoles in excellent yields. The method is operationally simple and highly efficient with broad functional group tolerance.
system was found to promote the Csp2–N bond-forming reaction utilizing N-tosylhydrazones and N-H azoles. This process shows functional group tolerance; di-, tri-, and tetrasubstituted N-vinylazoles were obtained in high yields. Under the optimized conditions, the reaction proceeds with high stereoselectivity depending on the nature of the coupling partners.
Transition-Metal-Free Synthesis of Pinacol Alkylboronates from Tosylhydrazones
作者:Huan Li、Long Wang、Yan Zhang、Jianbo Wang
DOI:10.1002/anie.201108139
日期:2012.3.19
Highly efficient: Pinacolalkylboronates were synthesized by the reaction of tosylhydrazones with bis(pinacolato)diboron or pinacolborane under transition‐metal‐free conditions. This reaction represents an expeditious conversion of carbonyl functionality into a boronate group.
C(sp)–C(sp<sup>3</sup>) Bond Formation through Cu-Catalyzed Cross-Coupling of<i>N</i>-Tosylhydrazones and Trialkylsilylethynes
作者:Fei Ye、Xiaoshen Ma、Qing Xiao、Huan Li、Yan Zhang、Jianbo Wang
DOI:10.1021/ja3004792
日期:2012.4.4
Copper-catalyzed cross-coupling of N-tosylhydrazones with trialkylsilylethynes leads to the formation of C(sp)-C(sp(3)) bonds. Cu carbene migratory insertion is proposed to play the key role in this transformation.