Ni- and Pd-Catalyzed Synthesis of Substituted and Functionalized Allylic Boronates

Abstract

Two highly efficient and convenient methods for the synthesis of functionalized and substituted allylic boronates are described. In one procedure, readily available allylic acetates are converted to allylic boronates catalyzed by Ni/PCy3 or Ni/PPh3 complexes with high levels of stereoselectivity and in good yields. Alternatively, the borylation can be accomplished with commercially available Pd catalysts [e.g. Pd2(dba)3, PdCl2, Pd/C] and starting with easily accessed allylic halides.

Total synthesis of xiamenmycin C and all of its stereoisomers: stereochemical revision

“…The amide moiety of xiamenmycin C could be synthesized from substituted methyl benzoate 6 via hydrolysis and amidation [6,7], while the key intermediate 6 might be formed through a highly regio-and diastereoselective oxidative cyclization [8] from 5, which, in turn, could be accessed from organoboron 3 via Suzuki-Miyaura coupling [9,10].…”

“…Thus, treatment of neryl acetate 2 with bis(pinacolato)diboron (B 2 Pin 2 ) in the presence of catalytic amount of bis(1,5-cyclooctadiene)nickel(0) (Ni(cod) 2 ) and tricyclohexylphosphine (PCy 3 ) [9] afforded the organoboron 3, which was subjected to the Suzuki-Miyaura coupling with MOM-protected methyl 3-bromo-4-hydroxybenzoate using [1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (Pd(dppf)Cl 2 ) [10] as catalyst to give the benzoate Z-5 in good yield.…”

Singular Metal Activation of Diboron Compounds

“…Since palladium complexes have proven to be efficient in activating diboron compounds throughout transmetalation, a wide range of applications have been considered in the last decade, such as palladium-catalyzed transformation of allylic alcohols to allylboronates, 69,70 borylation of allylic halides 71 or allylic acetates, 71,72 and the β-boration of α,β-unsaturated carbonyl substrates. 73 Interestingly, both palladium and nickel showed to be similarly efficient to activate B 2 pin 2 and catalyze the addition to unsaturated substrates.…”

Stereocontrolled Synthesis of 1,5‐Stereogenic Centers through Three‐Carbon Homologation of Boronic Esters

“…An alternative method was then required in order to achieve our goal. We drew inspiration from previous syntheses of allylic boronic esters through the Pd 0 -catalyzed borylation of allylic carbonates [10] and allylic alcohols [11] with B 2 pin 2 . These reactions are believed to occur through the reductive elimination of a Bpin-bound p-allyl-Pd II intermediate and generally result in high E selectivity.…”