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
Complete Stereoretention in the Rhodium-Catalyzed 1,2-Addition of Chiral Secondary and Tertiary Alkyl Potassium Trifluoroborate Salts to Aldehydes
作者:Abel Ros、Varinder K. Aggarwal
DOI:10.1002/anie.200901900
日期:——
Take your new partner by the hand: Chiralsecondary and tertiaryalkyltrifluoroboratesalts undergo rhodium‐catalyzed 1,2‐addition to aldehydes with completestereoretention (handedness) in all cases, enabling the creation of quaternary stereogenic centers with essentially perfect enantioselectivity (see scheme; cod=cycloocta‐1,5‐diene).
Regio‐ and Stereoselective Homologation of 1,2‐Bis(Boronic Esters): Stereocontrolled Synthesis of 1,3‐Diols and Sch 725674
作者:Alexander Fawcett、Dominik Nitsch、Muhammad Ali、Joseph M. Bateman、Eddie L. Myers、Varinder K. Aggarwal
DOI:10.1002/anie.201608406
日期:2016.11.14
1,2-Bis(boronic esters), derived from the enantioselective diboration of terminal alkenes, can be selectively homologated at the primary boronic ester by using enantioenriched primary/secondary lithiated carbamates or benzoates to give 1,3-bis(boronic esters), which can be subsequently oxidized to the corresponding secondary-secondary and secondary-tertiary 1,3-diols with full stereocontrol. The transformation
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
Construction of Multiple, Contiguous Quaternary Stereocenters in Acyclic Molecules by Lithiation-Borylation
作者:Charlotte G. Watson、Angelica Balanta、Tim G. Elford、Stéphanie Essafi、Jeremy N. Harvey、Varinder K. Aggarwal
DOI:10.1021/ja509029h
日期:2014.12.17
construction of two quaternary centers, this methodology fails. Instead, using mixed boranes (tBuBMe2), the synthesis of adjacent quaternary stereogeniccenters with full stereocontrol was successful. The process can be repeated two or three times in onepot leading to carbon chains bearing multiple contiguous quaternary stereogeniccenters. The boranes were converted into tertiary alcohols or C-tertiary amines
氨基甲酸酯锂化和硼酸化为硼试剂的同系化提供了一种强有力的方法。然而,当应用于受阻系统(带有 tBu-硼酸酯的二级氨基甲酸酯)以构建两个四元中心时,这种方法失败了。相反,使用混合硼烷 (tBuBMe2),具有完全立体控制的相邻四元立体中心的合成是成功的。该过程可以在一锅中重复两到三次,从而产生带有多个连续四元立体中心的碳链。使用氯胺将硼烷转化为叔醇或 C-叔胺。通过计算确定烷基对 Me 基团迁移的高选择性的起源。