Vinylidenation of Organoboronic Esters Enabled by a Pd‐Catalyzed Metallate Shift

Abstract

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.

Copper-Catalyzed 1,1-Boroalkylation of Terminal Alkynes: Access to Alkenylboronates via a Three-Component Reaction

“…Alkenylboronates are synthetically useful reagents in organic synthesis, which have been utilized in constructing various carbon–carbon and carbon–heteroatom bonds by metal-catalyzed cross-coupling reactions, especially in preparing multisubstituted alkenes . Given the great importance, the development of effective and practical protocols to synthesize multisubstituted alkenylboronates is highly desirable . To date, conventional methods to access alkenylboronates include transition-metal-catalyzed hydroboration of terminal alkynes and dehydrogenative borylation of alkenes (Scheme a).…”

π-Allylpalladium Complexes in Synthesis: An Update

“…In 2019, Morken and co-workers developed an efficient vinylidenation of organoboronic esters by a palladium-catalyzed metalate shift. 86 Treatment of boronic ester 214 (alkyl, alkenyl, or aryl) with an organolithium or Grignard reagent, produces quaternary boron 'ate' species 215. The allylpalladium complex is able to bind to such an 'ate' complex and promote the metalate shift toward an alkylpalladium intermediate.…”

α-Branched amines through radical coupling with 2-azaallyl anions, redox active esters and alkenes

“…The traditional approach to a-branched amines involves the addition of organometallic reagents, 5,6 such as Grignard reagents and organolithiums, to imines (Scheme 1a). [7][8][9][10] Recent years have witnessed remarkable progress in alternative syntheses of abranched amines. A more atom economical method employs transition-metal-catalyzed C-H bond activation followed by addition of the resulting organometallic nucleophile to imines (Scheme 1b).…”