Highly Enantioselective Synthesis of Tertiary Boronic Esters and their Stereospecific Conversion to other Functional Groups and Quaternary Stereocentres

Abstract

Organoboron compounds are useful in asymmetric synthesis. We have developed an efficient methodology for the highly enantioselective synthesis of tertiary boronic esters from the corresponding secondary benzylic alcohols. Further stereospecific transformations of the boronic ester moiety are described including the preparation of tertiary alcohols, C-tertiary amines and tertiary arylalkanes. Several homologations of tertiary boronic esters have also been developed for the construction of quaternary stereocentres.

Reagent-Controlled Lithiation–Borylation

“…Chiral tertiary boronic esters can also be used for the construction of challenging all-carbon quaternary stereogenic centers via functionalization protocols such as the Matteson homologation or the Zweifel olefination (see Scheme 12) [31]. This was applied in a short total synthesis of the natural product (À)-filiformin 68 (Scheme 18) [42].…”

“…The lithiation-borylation of this class of substrates has found considerable applications due to the further possible stereospecific transformations of the C-B into other functional groups (e.g., C-C, C-N, C-H) (Scheme 12) [31,32].…”

Enantiodivergent Synthesis of Allenes by Point‐to‐Axial Chirality Transfer

“…[7] We envisaged ac omplementary strategy in which an alkenyl boronic ester bearing an a-leaving group (LG 1 )i s homologated with an enantioenriched lithium carbenoid (Scheme 1B). [8] As tereospecific elimination process would then convert the resulting point-chiral intermediate into an axially chiral allene. [9] In such aprocess,there are two critical points at which selectivity must be controlled.…”

Chemoselective Boronic Ester Synthesis by Controlled Speciation

“…Herein we show that controlling the solution equilibria of boronic acid pinacol (BPin) and N-methyliminodiacetic acid (BMIDA) esters [7] during the course of a Suzuki-Miyaura cross-coupling event enables chemoselective formal homologation [8] of BPin esters (Figure 1 b). We also demonstrate the utility of this method to facilitate efficient iterative CÀC bond formation [9] and to enable the controlled oligomerization of sp 2 -hybridized BPin esters.…”