A Mechanistic Study of Direct Activation of Allylic Alcohols in Palladium Catalyzed Amination Reactions

Abstract

Abstract:We here report a computational approach on the mechanism of allylicamination reactions using allyl-alcohols and amines as the substrates and phosphoramidite palladium catalyst 1a, which operates in the presence of catalytic amount of 1,3-diethylurea as a co-catalyst. DFT calculations showed a cooperative hydrogen-bonding array between the urea moiety and the hydroxyl group of the allyl alcohol, which strengthens the hydrogen bond between the O-H moiety of the coordinated allyl-alcohol and the carbonyl-moiety of the ligand. This hydrogen bond pattern facilitates the (rate-limiting) C-O oxidative addition step and leads to lower energy isomers throughout the catalytic cycle, clarifying the role of the urea-moiety.

Supported Atomically Dispersed Pd Catalyzed Direct Alkoxylation and Allylic Alkylation†

“…In the realm of homogeneous Pd‐catalyzed direct allylic alkylation, the presence of hydrogen bonds formed between allyl alcohols, the solvent, or additives aids in hydroxyl group removal. [ 31‐34 ] For the heterogeneous Pd 1 /TiO 2 ‐EG system, we posit that localized hydrogen bonding established at the distinct atomically dispersed Pd site can equally facilitate allyl alcohol activation. To investigate this hypothesis, sodium carbonate (NaCO 3 ) was introduced into the reaction system (Table 1, entry 14).…”

Recent DFT Calculations on the Mechanism of Transition‐Metal‐Catalyzed C−O Activation of Alcohols

“…The early C−O bond activation of alcohols have proposed some remarkable breakthroughs as well as appealing reaction mechanisms [48–53] . Although limited by the experimental strategies or computational availability, these DFT findings have inspired the further exploitation of comprehensive and generalized activation solutions.…”

“…The early CÀ O bond activation of alcohols have proposed some remarkable breakthroughs as well as appealing reaction mechanisms. [48][49][50][51][52][53] Although limited by the experimental strategies or computational availability, these DFT findings have inspired the further exploitation of comprehensive and generalized activation solutions. This review presents selected mechanistic studies on these aspects of theoretical calculations in recent years, an in-depth discussion of the mechanisms and selectivity of the reactions, and a summary and outlook of the development prospects and potential challenges in this field.…”

Synergistic Organoboron/Palladium Catalysis for Regioselective N-Allylations of Azoles with Allylic Alcohols

“…In the absence of a co-catalyst, the reaction proceeded in 85% yield but low regioselectivity (1.3:1 N2:N1, entry 11). Presumably, the benzotriazole nucleophile is sufficiently acidic to promote the ionization of the allylic alcohol . Whereas tricyclic borinic acid 2b and diphenylborinate precatalyst 2c provided inferior results, screening of arylboronic acids revealed that these species also promoted the N1-selective pathway.…”