Iridium‐Catalyzed Chemo‐, Diastereo‐, and Enantioselective Allyl‐Allyl Coupling: Accessing All Four Stereoisomers of (E)‐1‐Boryl‐Substituted 1,5‐Dienes by Chirality Pairing

Abstract

Here, we report a highly chemo‐, diastereo‐, and enantioselective allyl‐allyl coupling between branched allyl alcohols and α‐silyl‐substituted allylboronate esters, catalyzed by a chiral iridium complex. The α‐silyl‐substituted allylboronate esters can be chemoselectively coupled with allyl electrophiles, affording a diverse set of enantioenriched (E)‐1‐boryl‐substituted 1,5‐dienes in good yields, with excellent stereoselectivity. By permuting the chiral iridium catalysts and the substrates, we efficiently and selectively obtained all four stereoisomers bearing two consecutive chiral centers. Mechanistic studies via density functional theory calculations revealed the origins of the diastereo‐ and chemoselectivities, indicating the pivotal roles of the steric interaction, the β‐silicon effect, and a rapid desilylation process. Additional synthetic modifications for preparing a variety of enantioenriched compounds containing contiguous chiral centers are also included.

Simultaneous Stereoinvertive and Stereoselective C(sp3)–C(sp3) Cross-Coupling of Boronic Esters and Allylic Carbonates

“…22 During the course of this work, Cho, Park, and co-workers reported a stereodivergent allyl−allyl coupling between branched allyllic alcohols and α-silyl-substituted allylboronate esters catalyzed by the same chiral iridium complex. 23 Nonetheless, a method enabling the use of more easily accessible boronic esters would provide a more general and broader chemical space for the concept of SimSS C(sp 3 )−C(sp 3 ) cross-coupling.…”

“…Herein, we describe our success in developing C­(sp 3 )–C­(sp 3 ) cross-coupling reactions of enantioenriched boronates ,, with π-allyl iridium complexes, which occur through a simultaneous stereoinvertive and stereoselective (SimSS) process, to construct vicinal stereogenic centers and show that this strategy can be used to create any enantiomer and diastereoisomer at will (Scheme c) . During the course of this work, Cho, Park, and co-workers reported a stereodivergent allyl–allyl coupling between branched allyllic alcohols and α-silyl-substituted allylboronate esters catalyzed by the same chiral iridium complex . Nonetheless, a method enabling the use of more easily accessible boronic esters would provide a more general and broader chemical space for the concept of SimSS C­(sp 3 )–C­(sp 3 ) cross-coupling.…”

Cross-Double Deoxygenative Carbon–Carbon Bond Formation between Benzyl Benzoates and Allylic Alcohols

“…The development of efficient and applicable methods for its construction is of significant importance and appealing to synthetic chemists. Allylation of the benzylic cation (Scheme a) and the π allyl metal complexes involved coupling reactions with allyl metals, benzyl anions, or benzylic radicals − (Scheme b) are well-established strategies . The requirement of strong Lewis acids and the limited availability of allyl nucleophiles (e.g., allyl silicon, allyl boron) in the former strategy have restricted the broad application.…”