Reactions of organoboron compounds enabled by catalyst-promoted metalate shifts

Abstract

This tutorial review describes recent developments in catalytic reaction design that involve catalyst-promoted 1,2-metalate shifts as a critical part of the reaction mechanism. Issues pertaining to catalysis, stereoselectivity, and reaction mechanism are discussed.

Scheme 1

1,2-Metalate shifts involving organoboron compounds.

Scheme 2

Catalytic asymmetric homologation by selective halide displacement.

Scheme 3

Sulfide-catalyzed cross-coupling by a metalate-shift-based pathway.

Scheme 4

Catalytic ring-opening of strained bicycles by 1,2-metalate shift.

Scheme 5

Early stoichiometric electrophile-induced metalate shifts involving unsaturated boron ‘ate’ complexes.

Scheme 6

Stoichiometric metalate shifts involving outer sphere and inner sphere addition to transition metal complexes.

Scheme 7

Catalytic synthesis of skipped dienes by addition of an alkynylborate to a Pd(allyl) complex with concomitant metalate shift.

Scheme 8

Ishikura’s Pd-catalyzed addition of indole borates to allyl electrophiles.

Scheme 9

Ready’s catalytic asymmetric coupling of indolylborates and allyl acetates.

Scheme 10

Studer’s catalytic stereoselective coupling of indolylborates and cyclopropanes by way of a metalate shift.

Scheme 11

Denmark’s catalytic asymmetric metalate rearrangement through sulfenium ion catalysis.

Scheme 12

Murakami’s Pd-catalyzed coupling of alkynylborates and aryl bromides.

Scheme 13

Murakami’s Pd-catalyzed coupling of alkynyl-9-BBN ‘ate’ complexes with aryl bromides, and the role of ligand.

Scheme 14

Mechanistic hypothesis for catalytic conjunctive cross-coupling by metal-induced metalate rearrangement.

Scheme 15

Catalytic enantioselective conjunctive cross-coupling.

Scheme 16

Catalytic conjunctive cross-coupling employing Grignard reagents.

Scheme 17

Catalytic asymmetric coupling of bis(alkenyl)borates provides allylboronic esters.

Scheme 18

Synthesis of tertiary organoboronic esters by conjunctive cross-coupling of α-substituted vinylboron ‘ate’ complexes.

Scheme 19

Conjunctive coupling of β-substituted alkenylboronates.

Scheme 20

(a) Kinetic analysis of conjunctive coupling reveals reaction 1 rate law. (b) Observation of the catalyst resting state supports kinetic analysis.

Scheme 21

Stereochemical and DFT analysis of conjunctive coupling. Ligand on Pd for DFT is dppf.

Scheme 22

Conjunctive coupling with Ni-based catalysts.

Scheme 23

Ni-catalyzed conjunctive coupling with C(sp³) electrophiles.

Scheme 24

Ni-catalyzed conjunctive coupling with C(sp³) electrophiles.

Scheme 25

A metalate shift in the course of Pd-catalyzed vinylidenation of boronic esters.