Direct Allylation of Active Methylene Compounds with Allylic Alcohols by Use of Palladium/Phosphine‐Borane Catalyst System

Abstract

The CÀC bond formation between active methylene compounds and allylic alcohols has been newly developed by using a palladium complex as a catalyst together with a phosphine-borane ligand. The best phosphine-borane ligand for this direct allylation has been revealed to be Ph 2 P(CH 2 ) 4 (9-BBN) to produce a variety of desirable allylated products in high yields.

Phosphine–Borane Ligands Induce Chemoselective Activation and Catalytic Coupling of Acyl Chlorides at Palladium

“…Our knowledge about their coordination properties has significantly progressed, but their application in transition metal catalysis is still in its infancy . Strikingly, ambiphilic ligands have been rarely employed in Pd catalysis so far, with only scant studies in allylation reactions (C–N and C–C coupling), addition reactions to enynes, Suzuki–Miyaura coupling, and hydrodechlorination . On the other hand, acyl chlorides have for some time attracted renewed interest in Pd catalysis on several grounds: (i) their preparation by carbonylation of aryl halides or shuttle catalysis, (ii) their use as substrates in cross-couplings, without or with decarbonylation, to form RCO–C or R–C bonds, and (iii) their use as a CO source in carbonylation reactions, including via functional group metathesis …”

Alcohols as Substrates in Transition-Metal-Catalyzed Arylation, Alkylation, and Related Reactions

“…Kimura and colleagues disclosed the allylation of 1,3-dicarbonyl compounds using a palladium catalyst alongside a phosphine/ borane ligand (Scheme 39b). 249 The authors found the Lewis acidity of the borane, along with the length of the linkage between the phosphorus and boron atoms, were significant in achieving high yields. The authors proposed that Lewis acid− base coordination of the alcohol with the boron atom of the ligand occurred concurrent with palladium coordination to the unsaturated bond in the allyl alcohol, leading to C−O bond cleavage and the generation of a π-allyl complex.…”

“…While the reaction proceeded in the absence of an exogenous Brønsted acid catalyst, the inclusion of formic acid was found to improve the reaction yield. Kimura and colleagues disclosed the allylation of 1,3-dicarbonyl compounds using a palladium catalyst alongside a phosphine/borane ligand (Scheme b) . The authors found the Lewis acidity of the borane, along with the length of the linkage between the phosphorus and boron atoms, were significant in achieving high yields.…”

Insights into Substrate Self-Assisted Activation of Allylic Alcohols Guiding to Mild Allylic Substitution of Tautomerizable Heteroarenes

“…In recent years, some additional activator-free Tsuji–Trost reactions of allylic alcohols have been developed. − However, the activation mechanisms of allylic alcohols were investigated only in rare reports and were mainly based on theoretical calculations . Therefore, it is still highly desirable to illuminate the activation mechanism of activator-free Tsuji–Trost reactions especially by simple and facile experimental methods …”