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
The KHMDS-catalyzed tertiary alkylation of aldehydes, ketones or imines using tertiary benzylic organoboronates is reported. This protocol permitted the use of tertiary benzylic alkylboronates as t...
The transition‐metal‐free cross‐coupling of alkyl or aryl electrophiles by using tertiary benzylic organoboronates is reported. This reaction involves the generation of tertiary alkyl anions from organoboronates in the presence of an alkoxide base and then their substitution reactions. This protocol allows the simple and efficient construction of quaternary carbon centers.
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.
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).