Improved method for the conversion of pinacolboronic esters into trifluoroborate salts: facile synthesis of chiral secondary and tertiary trifluoroborates
作者:Viktor Bagutski、Abel Ros、Varinder K. Aggarwal
DOI:10.1016/j.tet.2009.10.002
日期:2009.11
A general method for the preparation of virtually any potassium trifluoroborate salt from the corresponding pinacolboronic ester is reported. Thus, conditions for an azeotropic removal of pinacol from the reaction mixture were found to afford the desired potassium trifluoroborates of sufficient purity (>95%) in nearly quantitative yields irrespective of the nature of the product. The utility of this
Protodeboronation of Tertiary Boronic Esters: Asymmetric Synthesis of Tertiary Alkyl Stereogenic Centers
作者:Stefan Nave、Ravindra P. Sonawane、Tim G. Elford、Varinder K. Aggarwal
DOI:10.1021/ja1084207
日期:2010.12.8
tertiary boranes undergo efficient protodeboronation with carboxylic acids, tertiary boronicesters do not. Instead, we have discovered that CsF with 1.1 equiv of H2O (on tertiary diarylalkyl boronicesters) or TBAF·3H2O (on tertiary aryldialkyl boronicesters) effect highly efficient protodeboronation of tertiary boronicesters with essentially complete retention of configuration. Furthermore, substituting
Enantioselective installation of adjacent tertiary benzylic stereocentres using lithiation–borylation–protodeboronation methodology. Application to the synthesis of bifluranol and fluorohexestrol
作者:Stefan Roesner、Daniel J. Blair、Varinder K. Aggarwal
DOI:10.1039/c4sc03901g
日期:——
Highly hindered benzylic carbamates have been reacted with hindered boronic esters to give tertiary boronic esters with very high diastereo- and enantiocontrol and the methodology has been applied to otherwise difficult-to-access molecules.
Transition-metal-free synthesis of 1,1-diboronate esters with a fully substituted benzylic center via diborylation of lithiated carbamates
作者:Haonan Zhao、Min Tong、Haijun Wang、Senmiao Xu
DOI:10.1039/c7ob00654c
日期:——
lithiation-borylation method has been developed to access a variety of 1,1-diboronate esters with a fully substituted benzylic center from readily available secondary benzylic N,N-diisopropyl carbamates. The method is applicable to scale-up synthesis of 1,1-diboron compounds. Furthermore, the current method is also applicable to synthesizing opticallyactive 1,1-silylboronate esters.
Full Chirality Transfer in the Conversion of Secondary Alcohols into Tertiary Boronic Esters and Alcohols Using Lithiation-Borylation Reactions
作者:Viktor Bagutski、Rosalind M. French、Varinder K. Aggarwal
DOI:10.1002/anie.201001371
日期:——
New conditions, full transfer: Using MgBr2/MeOH as an additive now provides essentially 100 % retention of configuration in the lithiation–borylation reaction, thus leading to tertiaryboronicesters (or tertiary alcohols) with exceptionally high ee values in all cases—even with rather hindered substrates and more stabilized lithiated carbamates (see scheme; Cb=carbamate, pin=OCMe2CMe2O).