Triethylborane as an efficient promoter for palladium-catalyzed allylation of active methylene compounds with allyl alcohols

Au-Catalyzed Formal Allylation of Diazo(thio)oxindoles: Application to Tandem Asymmetric Synthesis of Quaternary Stereocenters

We report an efficient Au(I)-catalyzed formal allylation of diazo(thio)oxindoles using allyltrimethylsilane to give 3-allyl (thio)oxindoles, which are difficult to access by using traditional alkylation methods under basic conditions. The approach enables a highly stereoselective synthesis of quaternary (thio)oxindoles via a formal allylation-asymmetric Michael addition sequence. These adducts are versatile synthons for spirocyclic (thio)oxindoles. Initial biological studies reveal that chiral thiooxindoles show promising antiproliferation activity that is better than that of the corresponding oxindoles.

Et3B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita-Baylis-Hillman alcohols

A practical and efficient palladium-catalyzed direct allylation of β-dicarbonyl compounds with both cyclic and acyclic Morita–Baylis–Hillman (MBH) alcohols, using Et₃B as a Lewis acid promoter, is described herein. A wide range of the corresponding functionalized allylated derivatives have been obtained in good yields and with high selectivity.

Transition metal-catalyzed allylic substitution reactions with unactivated allylic substrates

This review highlights recent developments in the area of transition metal-catalyzed allylic substitution reactions with unactivated allylic substrates.

Reaction of alcohols and silyl ethers in the presence of an indium/silicon-based catalyst system: Deoxygenation and allyl substitution

An In(III)/Si catalyst system effects the direct allyl substitution of alcohols and silyl ethers under mild conditions. A deoxygenation of alcohols is also promoted by InCl3 catalyst. This method requires no pretreatment or protection of hydroxy groups or deprotection of siloxy groups. The completion of the catalytic allylation depends on the low oxophilicity and high halophilicity of In(III) halide species, and other representative Lewis acids such as AlCl3 and BF3 have no catalytic activity for the allylations. The oxophilicity and halophilicity are also demonstrated by NMR studies.

Palladium-catalyzed selective activation of allyl alcohols as allyl cations, allyl anions, and zwitterionic trimethylenemethanes

Pd-Et3B catalytic system promotes the generation of allyl cations, allyl anions, and zwitterionic trimethylenemethane species from the corresponding allylic alcohols. Allyl cations react with a wide variety of nucleophiles, e.g., amines, active methylene compounds, 1,3,5-trihydroxybenzene, indoles, aldehydes (at the α-position). The reaction is extended to dehydrative Grob fragmentation of 1,3-diols. Allyl anions react with aldimines to give homoallyl amines. Zwitterionic trimethylenemethane, generated from 2-methylene-1,3-propanediol, reacts with aldehydes and aldimines to provide 3-methylenecyclopentanols and 3-methylenepyrrolidines, respectively. Vinyl epoxide can be utilized as a synthetic equivalent of 3-butenyl 2-anion-1-cation.

Palladium-triethylborane-triggered direct and regioselective conversion of allylic alcohols to allyl phenyl sulfones

A combination of Pd(OAc)2 (5 mol %), PPh3 (10 mol %), and Et3B (200 mol %) promotes the formation of allyl phenyl sulfones from the allylic alcohols directly with excellent yields under mild conditions. The activation of an alcohol group is not necessary which is achieved in situ. The conjugated dienols also were equally effective for the said transformation.

Pd-Catalyzed C3-Selective Allylation of Indoles with Allyl Alcohols Promoted by Triethylborane

Under palladium catalysis, Et3B nicely promotes allyl alcohols to undergo C3-selective allylation of indoles and tryptophan; the yields range 75-95%.

Pd(0)-Catalyzed Amphiphilic Activation of Bis-allyl Alcohol and Ether

Pd(0).Et3B catalyzes amphiphilic activation of symmetric allylic diol 1 to promote electrophilic allylation at the alpha-position of aldehydes and nucleophilic allylation at the aldehyde CO, furnishing 3-methylenecyclopentalols 2 and thus generation of a zwitterionic trimethylenemethane species from the commercially available diol 1.