Organoboron ‘ate’ complexes undergo a net vinyl insertion reaction to give 1,1-disubstituted alkenyl boronic esters when treated with stoichiometric allyl acetate and a palladium catalyst. Reactions that employ vinyllithium afforded good to excellent yields after one hour, while reactions that employ vinylmagnesium chloride furnished modest to good yields after 18 hours.
Application of the boron-Wittig reaction to ketone electrophiles provides a straightforward route to trisubstituted alkenylboronic esters. With either pentamethyldiethylenetriamine or trimethyl-1,4,7triazacyclononane additive, the olefination can occur with very high levels of stereocontrol and in good chemical yield.
Organoboron “ate” complexes undergo a net vinyl insertion reaction to give 1,1‐disubstituted alkenyl boronic esters when treated with stoichiometric allyl acetate and a palladium catalyst. Reactions that employ vinyllithium afforded good to excellent yields after one hour, while reactions that employ vinylmagnesium chloride furnished modest to good yields after 18 hours.
Palladium-catalyzed conjunctive cross-coupling can be
accomplished
with the use of chiral phosphine-oxazoline based ligand structures.
Of note, the reaction can be conducted on Grignard-based boron ate
complexes and operates without the use of halide-scavenging additives,
which are required for other catalyst systems.
Synthesis of stereodefined carbocyclic and heterocyclic tertiary boronic esters is accomplished by performing a conjunctive cross-coupling reaction on preformed cyclic boron ate complexes. Boronates bearing spirocyclic and aryl bicyclic skeletons can be synthesized enantioselectively using a chiral PHOX-ligated Pd catalyst with achiral starting material, while substrates bearing continuous stereogenic centers can be generated diastereoselectively. A variety of aryl and alkenyl electrophiles are incorporated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.