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.     

Silyl-substituted 1,3-butadienes for Diels-Alder reaction, ene reaction and allylation reaction

Silyl-substituted 1,3-butadienes are useful building blocks and are readily applied in several types of reactions such as Diels-Alder reaction, ene reaction and allylation. They can also participate in different tandem reactions such as Diels-Alder/allylation, ene/allylation, ene/allylation/Diels-Alder reaction, ene/allylation/ene reaction and ene/allylation/Diels-Alder/allylation reaction. This feature article reviews the synthesis of silyl-substituted 1,3-butadienes, and their applications in the reaction types mentioned above, involving a tandem Diels-Alder/ene/allylation process. This article also introduces some reactions of alkenylsilanes and allylsilanes for comparison and discussion about the tandem reaction. The tandem reactions described in this article are a powerful tool to construct complicated multicyclic compounds with high selectivity and high efficiency.     

C＝N双键的不对称烯丙基化反应

详细地综述了有关C＝N双键立体选择性烯丙基化反应的研究进展. 重点讲述了使用手性辅助基团、手性试剂以及不对称催化剂进行C＝N双键不对称烯丙基化的方法.     

Synthesis of N,N-bis(3-butenyl)amines from 2-azaallyl dication synthetic equivalents and conversion to 2,3,6,7-tetrahydroazepines by ring-closing metathesis

N,N-Bis(3-butenyl)amines can be prepared by the double allylation of either (2-azaallyl)stannanes or (2-azaallyl)nitriles, both of which thereby act as synthetic equivalents to amine alpha,alpha'-dications (2-azaallyl dications). Allylmagnesium bromide is the reagent of choice for the double allylation of both substrates, although allyllithium also effects the double allylation of (2-azaallyl)nitriles. Ring-closing metathesis can be performed on the N-protected amines, or with in situ protonation, on the free amines to provide 2,3,6,7-tetrahydroazepines. (2-Azaallyl)nitriles can also be monoallylated to provide N-(3-butenyl)aminonitriles, whereas the double allylation of (2-azaallyl)stannanes cannot be stopped at monoallylation. (2-Azaallyl)silanes undergo monoallylation to give N-(3-butenyl)aminosilanes but do not undergo double allylation.     

金属参与的水相烯丙基化反应

近30年来,水介质中碳-碳键的形成一直是研究的热点,其优越性也逐渐被人们所认知。在已发现的水相金属有机反应中,水相烯丙基化反应是研究得较多和较深入的反应之一。水相烯丙基化反应由于其发展速度较快,新的金属及金属体系参与的烯丙基化反应以及水相烯丙基化反应的机理研究不断被报道。本文综述了水相中金属参与烯丙基化反应的最新研究进展,并对新的反应机理作了简要的阐述。     

Selective O‐allylation of bisphenol A: toward a chloride‐free route for epoxy resins

The O‐allylation of bisphenol A (BPA) has been performed with the most selective catalysts for O‐allylation of phenols reported previously. Both the cyclopentadienyl–ruthenium catalysts and the palladium–diphosphine catalysts are capable of selectively performing single and double O‐allylation of BPA. An intriguing solvent effect is observed; the choice of the solvent is of key importance for both conversion and selectivity. The use of an excess of diallyl ether as allylating agent results in relatively high yields of the bisallyl ether of bisphenol A, while maintaining the high selectivity for O‐allylation. Copyright © 2010 John Wiley & Sons, Ltd.     

Efficient allylation of aldehydes promoted by carboxylic acids

A variety of carboxylic acids have been screened for mediating the allylation of aldehydes with allytributyltin in different solvents. A novel, general, and practical method of allylation of aldehydes promoted by carboxylic acids under mild reaction conditions has been developed. Among them, p-nitrobenzoic acid afforded high to quantitative yields of the homoallylic alcohol products, and can be easily recovered after workup by aqueous HCl. Glyoxylic acid self-catalyzed the allylation without adding any other promoter or catalyst to give the corresponding allylation product in good yield. The regioselectivity of the crotylation of aldehydes is tunable by controlling the acidity of the carboxylic acids. The crotylation of aldehydes produced the alpha-adduct as major products in moderate to good yields with CF(3)CO(2)H as a promoter. A possible mechanism for the allylation is also discussed.     

Electrophilic substitution of organosilicon compounds. II. Synthesis of allyl-terminated polyisobutylenes by quantitative allylation of tert-chloro-polyisobutylenes with allyltrimethylsilane

Essentially quantitative allylation of linear and three-arm star tert-chloro capped polyisobutylenes [^tCl–PIB–Cl^t and PIB(Cl^t)₃] has been achieved by the use of allyltrimethylsilane (AllylSiMe₃) and Friedel–Crafts acids. Quantitative allylation occurs under suitable conditions, e.g., slight molar excess of TiCl₄ and AllySiMe₃ polar media, ?70°C. These conditions have been developed from quantitative model allylation experiments using 2,4,4-trimethyl-2-chloropentane. Essentially quantitative allylation occurs with long-chain or “once fired” tert-chloro-end groups. Complete allylation can also be effected in a “one-pot two-step” synthesis, i.e., by first preparing the tert-chloro-ended PIB by the inifer method and without isolating the product, completing the synthesis by allylation in the same reactor. Extensive but not quantitative allylation can also be obtained in situ, i. e., during polymerization, by the use of the AllylSiMe₃/cumyl chloride/BCI₃/isobutylene combination. While allylation proceeds with great ease under the mildest conditions, e.g., ?70°C, vinylation with vinyltrimethylsilane could not be achieved even under more forcing conditions.     

Tin mediated Barbier type allylation in ionic liquids

The Barbier type allylation of carbonyl compounds is a useful organic transformation as the resultant homoallylic alcohols are important building blocks for many biologically active molecules. Tin mediated Barbier allylation of different carbonyl compounds in room temperature ionic liquid, [BMIM][BF₄] afforded the corresponding homoallylic alcohols in good to excellent yields. The ionic liquid was successfully recycled and reused in allylation reactions.     

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.     

Microwave-enhanced cross-coupling of allyl chlorides with vinyltrifluoroborates

The allylation of potassium alkenyltrifluoroborates with allyl chloride via a palladium catalyzed cross-coupling reaction occurs rapidly under microwave irradiation. The allylation reaction produces 1,4-pentadienes in high yields.     

A concise synthetic route to the conduritols from pentoses

A short synthetic strategy for preparation of the conduritols is described. The key step employs a zinc-mediated fragmentation of protected methyl 5-deoxy-5-iodo-d-pentofuranosides followed by an allylation of the intermediate aldehyde in the same pot. The allylation is performed with 3-bromopropenyl benzoate and occurs with good diastereoselectivity. An amino group can be introduced in the product by trapping the intermediate aldehyde as the imine prior to the allylation. The functionalised 1,7-octadienes, thus obtained, are converted into protected conduritols by ring-closing olefin metathesis.     

Stereoselective allylation reactions of acyclic and chiral α-amino-β-hydroxy aldehydes 3: Total synthesis of (+)-1-epi-castanospermine

Stereoselective allylation reactions of acyclic, chiral α-amino-β-hydroxy aldehydes containing four contiguous stereocenters were conducted. Allylation mediated by MgBr₂?OEt₂ afforded the anti-product. A plausible mechanism of the allylation reaction is also described. The resulting allylation product was used for the total synthesis of (+)-1-epi-castanospermine.     

Microwave-assisted catalytic allylation of aldehydes promoted by a mesoporous silica-supported BINOL ligand in solid media

An efficient and operationally simple method for catalytic allylation has been developed and its application in the microwave-assisted catalytic allylation of aldehydes in solid media was investigated.     

Efficient allylation of aldehydes with allyltributylstannane catalyzed by CuI

Cuprous iodide has been found to be a very effective catalyst for allylation of aldehydes with allyltributylstannane. The catalytic system efficiently promotes the allylation reaction in DMF to produce homoallylic alcohols in high yield.     

Amidyl Radical Directed Remote Allylation of Unactivated sp3 C−H Bonds by Organic Photoredox Catalysis

The development of visible‐light‐mediated allylation of unactivated sp³ C?H bonds is reported. The remote allylation was directed by the amidyl radical, which was generated by photocatalytic fragmentation of a pre‐functionalized amide precursor. Both aromatic and aliphatic amide derivatives could successfully deliver the remote C?H allylation products in good yields. A variety of electron deficient allyl sulfone systems could be used as δ‐carbon radical acceptor.     

A convenient and efficient route for the allylation of aromatic amines and alpha-aryl aldehydes with alkynes in the presence of a Pd(0)/PhCOOH combined catalyst system

The allylation of aromatic amines with alkynes proceeded smoothly in the presence of catalytic amounts of Pd(PPh(3))(4) and benzoic acid. The allylation products were obtained in high yields in a regio- and stereoselective manner. The effect of various groups on the nitrogen atom of anilines was studied. Regardless of the substituent (electron withdrawing or electron donating) on the aromatic ring, the reaction proceeded well. Various functionalities, including -CH(3), -OMe, -Cl, -CN, -COOMe, -NO(2) and -COCH(3) were tolerated under the reaction conditions. Similarly, the allylation of alpha-aryl aldehydes proceeded well with the same level of regio- and stereoselectivity as the allylation of aromatic amines. This reaction provides the second example of the transition metal catalyzed direct alpha-allylation of aldehydes.     

Indium(I)/CuFe2O4 Reagent for Allylation of Carbonyls and Epoxide Rearranged Carbonyls

Russian Journal of General Chemistry - Indium(I)/CuFe2O4 reagent for carbonyl allylation and epoxide rearranged carbonyl allylation is proposed for formation of homoallylic alcohols. The In(I)...     

New heterogenized catalytic systems in norbornadiene allylation

New heterogenizated catalysts for the allylation of norbornadiene (NBD) were prepared by the adsorption immobilization and surface assembly methods. The obtained catalysts were screened in the allylation of NBD, and the main technological parameters of the process were determined.     

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.