Deacylative allylation: allylic alkylation via retro-Claisen activation

A new method for allylic alkylation of a variety of relatively nonstabilized carbon nucleophiles is described herein. In this process of "deacylative allylation", the coupling partners, an allylic alcohol and a ketone pronucleophile, undergo in situ retro-Claisen activation to generate an allylic acetate and a carbanion. In the presence of palladium, these reactive intermediates undergo catalytic coupling to form a new C-C bond. In comparison to unimolecular decarboxylative allylation, a commonly utilized method for allylation of carbon anions, deacylative allylation is an intermolecular process. Moreover, deacylative allylation allows the direct coupling of readily available allylic alcohols. Lastly, the full utility of deacylative allylation is demonstrated by the rapid construction of a variety 1,6-heptadienes via 3-component couplings.     

Enantioselective C3-Allylation of Pyridines via Tandem Borane and Palladium Catalysis

Herein, we report a one-pot method for enantioselective C−H allylation of pyridines at C3 via tandem borane and palladium catalysis. This method involves borane-catalyzed pyridine hydroboration to generate dihydropyridines, then palladium-catalyzed enantioselective allylation of the dihydropyridines with allylic esters, and finally air oxidation of the allylated dihydropyridines to afford the products. This method enables the introduction of an allylic group at C3 with excellent regio- and enantioselectivities.     

Iridium‐Catalyzed Regio‐ and Enantioselective Allylic Substitution of Trisubstituted Allylic Electrophiles

The first Ir‐catalyzed enantioselective allylation of trisubstituted allylic electrophiles has been developed. Through modification of the leaving group of allylic electrophiles, we found that trisubstituted allylic phosphates are suitable electrophiles for asymmetric allylation. The reaction of allylic phosphates with enol silanes derived from dioxinones gave allylated products in good yields with high enantioselectivities.     

Palladium-catalyzed asymmetric umpolung allylation of imines with allylic alcohols

A palladium-catalyzed asymmetric umpolung allylation reaction of imines with allylic alcohols has been developed. In the presence of chiral spiro phosphoramidite ligand 4, the allylation was accomplished with high yields and good enantioselectivities. The use of highly stable and easily available allylic alcohols instead of allylic metal reagents facilitated the preparation of chiral homoallylic amines.     

From allylic alcohols to chiral tertiary homoallylic alcohol: palladium-catalyzed asymmetric allylation of isatins

A palladium-catalyzed asymmetric allylation of isatins with allylic alcohols as an allyl donor was developed by using chiral spiro phosphoramidite ligands. A variety of chiral tertiary homoallylic alcohols 3-allyl-3-hydroxy-2-oxindoles were prepared directly from allylic alcohols in one step with excellent yields and moderate enantioselectivities. This represents the first catalytic asymmetric allylation of ketones with allylic alcohol as the allylating agent.     

A straightforward access to pyrrolidine-based ligands for asymmetric synthesis

A straightforward and flexible method for the preparation of ligands based on the pyrrolidine scaffold is presented. The synthetic strategy involves a diastereoselective allylation of phenylglycinol-derived imines, followed by a cyclization promoted by a hydrozirconation/halogenation sequence. Enantioselectivities of up to 84% ee in the asymmetric allylic allylation were obtained using these ligands.     

Aromatic allylation via diazotization: variation of the allylic moiety and a short route to a benzazepine derivative

A continued study of the recently discovered diazotizative allylation (DiazAll) reaction of aniline derivatives is reported. Several allyl reagents, commonly used in radical allylation reactions, were evaluated, and some of these reagents resulted in allylation when used in the DiazAll reaction. The best result was obtained with allyl bromide. Substituted allylic bromides gave the corresponding allyl aromatic compounds in poor to excellent yields. In comparison with an established method for aromatic allylation, the DiazAll reaction performed well and was superior when a more complex allylic bromide was used. Finally, a new allylation-bromocyclization reaction was demonstrated and used in the synthesis of a known inhibitor of phenylethanolamine N-methyltransferase (PNMT), an enzyme involved in the biosynthesis of adrenaline.     

Allyation of carbonucleophiles with allylic carbonates under neutral conditions catalyzed by rhodium complexes

Rhodium-phosphine complexes catalyze the allylation of carbonucleophiles with allylic carbonates under neutral conditions. In addition, we found unusual regioselectivity in the rhodium catalyzed allylation.     

Direct Allylation of In Situ Generated Aldehyde Acyl Anions by Synergistic NHC and Palladium Catalysis

The direct regioselective allylation of in situ generated aldehyde acyl anions has been achieved by synergistic NHC and Pd catalysis. It provides an efficient access to valuable β,γ‐unsaturated ketones under mild reaction conditions starting from easily accessible allylic carbonates and aldehydes without any preactivation. The synergistic catalysis method demonstrated herein adds a new dimension to the area of metal‐mediated C allylation.     

Chiral phosphoramide-catalyzed enantioselective addition of allylic trichlorosilanes to aldehydes. Preparative studies with bidentate phosphorus-based amides

On the basis of the mechanistic insight that more than one Lewis basic moiety (phosphoramide) is involved in the rate- and stereochemistry-determining step of enantioselective allylation, bidentate chiral phosphoramides were developed. Different chiral phosphoramide moieties were connected by tethers of methylene chains of varying length. The rate and enantioselectivity of allylation with allyltrichlorosilane promoted by the bidentate phosphoramides was found to be highly dependent on the tether length. A new phosphoramide based on a 2,2'-bispyrrolidine skeleton has been designed and afforded good yield, efficient turnover, and high enantioselectivity in allylation reactions. The synthesis of enantiopure 2,2'-bispyrrolidine was easily accomplished on large scale by photodimerization of pyrrolidine followed by resolution with L(or D)-tartaric acid. The scope of the allylation reaction was examined with variously substituted allylic trichlorosilanes and unsaturated aldehydes. This method has been applied to the construction of stereogenic, quaternary centers by the addition of unsymmetrically gamma-disubstituted allylic trichlorosilanes.     

环烯丙基溴在Cu/SnCl2参与的水相羰基烯丙基化反应中的应用

Five- and six-membered cyclic allylic halides were found to be much less reactive than the acyclic allylic halides in aqueous allylation reactions. Nevertheless, it was found that SnC12/Cu was powerful enough to mediate the aqueous allylation reactions involving cyclic allylic halides. Both the aliphatic and aromatic aldehydes could be efficiently allylated and the reaction condition was mild, simple and safe. The yields were usually in 75%-97% and the reaction was erythro selective.     

Allylic tantalums as highly imine-selective reagents

A practical method for the allylation of low electrophilic N-aliphatic imines was established by allylic tantalum. This is a superior methodology compared with conventional ones in terms of wide applicability to imines.     

Regiodivergent Hydroaminoalkylation of Alkynes and Allenes by a Combined Rhodium and Photoredox Catalytic System

A rhodium/photoredox dual catalyzed regiodivergent α‐allylation of amines is described. As an atom‐economic and efficient method, alkynes and allenes are used as allylic electrophile surrogates in this novel protocol. With different reaction conditions, synthetically useful branched or linear homoallylic amines could be synthesized in good to excellent yields and regioselectivity. This straightforward strategy complements the traditional transition‐metal catalyzed allylation reactions.     

Simple palladium‐catalyzed C–N bond formation for poor nucleophilicity of aminonaphthalenes

Aromatic amines is not used commonly in allylic amination, presumably because of their less nucleophilic nature compared with the more extensively used benzylamine or relatively stable anionic nitrogen nucleophiles. An eco‐friendly method for C–O bond activation of allylic acetates using palladium associated with ligands in water leading to N‐allylation was described in this study. The palladium‐catalyzed allylic amination of allylic acetate with aminonaphthalenes gave 34–95% yields to the corresponding N‐allylic aminonaphthalenes. Copyright © 2011 John Wiley & Sons, Ltd.     

A mechanistic study of the Hiyama-Nozaki allylation: evidence for radical intermediates

In course of chromium(II) mediated additions of relatively complex allylic bromides to aldehydes (Hiyama-Nozaki allylation) radical intermediates have been observed. From these findings a new mechanism of the allylation is derived.     

Facile Palladium catalyzed decarboxylative allylation of active methylene compounds under neutral conditions using allylic carbonates

Palladium catalyzed decarboxylative allylation of active methylene compounds proceeded under mild neutral conditions using allylic carbonates, which are much more reactive than allylic acetates or phenoxides used commonly in the reaction.     

Chiral Counteranion Strategy for Asymmetric Oxidative C(sp3)H/C(sp3)H Coupling: Enantioselective α‐Allylation of Aldehydes with Terminal Alkenes

The first enantioselective α‐allylation of aldehydes with terminal alkenes has been realized by combining asymmetric counteranion catalysis and palladium‐catalyzed allylic C? H activation. This method can tolerate a wide scope of α‐branched aromatic aldehydes and terminal alkenes, thus affording allylation products in high yields and with good to excellent levels of enantioselectivity. Importantly, the findings suggest a new strategy for the future creation of enantioselective C? H/C? H coupling reactions.     

Direct palladium/carboxylic acid-catalyzed allylation of anilines with allylic alcohols in water

The direct activation of C-O bonds in allylic alcohols in water as a suspension medium by palladium complexes has been accelerated by carrying out the reactions in the presence of a carboxylic acid. The palladium-catalyzed allylation of anilines using allylic alcohols directly gave allylic anilines in good yields.     

Palladium-catalyzed reactions of hypophosphorous compounds with allenes, dienes, and allylic electrophiles: methodology for the synthesis of allylic h-phosphinates

Hypophosphorous compounds (MOP(O)H(2), M = H, R(3)NH) effectively participate in metal-catalyzed C-P bond-forming reactions with allenes, dienes, and activated allylic electrophiles under mild conditions. The catalytic system Pd(2)dba(3)/xantphos is crucial to avoid or minimize the competitive reductive transfer-hydrogenation pathway available to hypophosphorous acid derivatives. Further investigation into the allylation mechanism provided access to the analogy allylic acetate-allylic phosphinate, which then led to the development of a Pd-catalyzed rearrangement of preformed allylic phosphinates esters and, ultimately, to a catalytic dehydrative allylation of hypophosphorous acid with allylic alcohols. The reactions disclosed herein constitute efficient synthetic approaches, not only to prepare allylic H-phosphinic acids but also their esters via one-pot tandem processes. In addition, the potential of H-phosphinates as useful synthons for the preparation of other organophosphorus compounds is demonstrated.     

Chiral Counteranion Strategy for Asymmetric Oxidative C(sp3)?H/C(sp3)?H Coupling: Enantioselective α‐Allylation of Aldehydes with Terminal Alkenes

The first enantioselective α‐allylation of aldehydes with terminal alkenes has been realized by combining asymmetric counteranion catalysis and palladium‐catalyzed allylic C H activation. This method can tolerate a wide scope of α‐branched aromatic aldehydes and terminal alkenes, thus affording allylation products in high yields and with good to excellent levels of enantioselectivity. Importantly, the findings suggest a new strategy for the future creation of enantioselective C H/C H coupling reactions.