Stereocontrolled palladium-catalysed umpolung allylation of aldehydes with allyl acetates

In the present work the stereocontrolled palladium-catalysed umpolung allylation of aldehydes is described. Allyl acetates are in situ transformed into the corresponding allyl boronates, which directly react with aldehydes. The question of stereocontrol is raised by employing (a) chiral boronating agents (reagent control) and by (b) utilising chiral aldehydes (substrate control). These studies reveal that the approach based on substrate control is superior to the former one with respect to yields and stereoselectivity. Remarkably, this umpolung protocol often yields the 4,5-syn products in high selectivity, which is unprecedented for direct crotylations.     

The direct thioesterification of aldehydes with disulfides via NHC-catalyzed carbonyl umpolung strategy

An efficient N-heterocyclic carbene (NHC)-catalyzed direct thioesterification of aldehydes and α,β-unsaturated aldehydes (enals) with diaryl disulfides is reported. The protocol involves carbonyl umpolung reactivity of aldehydes and enals in which the carbonyl carbon attacks nucleophilically on diaryl disulfides to afford thioesters and α,β-unsaturated thioesters, respectively. However, aliphatic aldehydes are not suitable substrates for this reaction. No by-product formation, complete atom-economy, shorter reaction time, ambient temperature, operational simplicity, and high yields are the salient features of the present procedure.     

结构新颖的金属双核烯丙基试剂的合成及其芳香醛烯丙基化反应

报道了一个简捷的芳香醛的烯丙基化反应的新体系. 通过使用新型的金属双核烯丙基锡试剂(含有Sn—M键, M=Mn或Fe)与醛在二氯甲烷中反应, 无需使用任何辅助试剂, 直接得到较高产率(42％~98％)的高烯丙基醇. 实验结果证明过渡金属基团及M—Sn键具有相当高的活化锡原子上的烯丙基基团的作用.     

Benzylation and Allylation of Naphthols Using Amberlyst-15

A simple and efficient method has been developed for benzylation and allylation of naphthols by treatment of the compounds with benzylic and allylic alcohols, respectively, in the presence of amberlyst-15. Several heterogeneous catalysts were screened for the reaction, and amberlyst-15 was found to be most effective.     

Construction of multifunctional heterocycles bearing aza-quaternary carbons by titanocene-catalyzed umpolung reactions

The combined application of Grignard/Reformatsky addition and the titanocene-catalyzed umpolung α-amino carbon-carbon bond formations provided a flexible and versatile protocol for preparation of multifunctional pyrrolidinones/piperidinones/N-Boc-piperidines bearing aza-quaternary carbons (AQC) from cyclic imides and analogues. Based on these multifunctional single-ring motifs, several advanced AQC-bearing heterocycles, such as AQC-possessing indolizidines and 1-azaspirocycles, have been constructed efficiently.     

Nucleophilic allylation of N,O-acetals with allylic alcohols promoted by Pd/Et3B and Pd/Et2Zn systems

Pd/Et₃B and Pd/Et₂Zn systems promote the nucleophilic allylations of 2-aminotetrahydrofuran and 2-aminotetrahydropyran with allylic alcohols to provide ω-hydroxyhomoallylamines in high yields. The transformation is applicable to the allylation of non-protective carbohydrates, such as ribose and deoxyribose.     

Allylation of cyclohexanones in aqueous media and influence of facial amphiphilic fructopyranosides

The indium-catalyzed allylation reaction was performed in good yields and short reaction time with various cyclohexanones in water. Aqueous facial amphiphilic carbohydrates solutions were also screened for their potency to modify the stereochemical outcome of the reaction.     

An efficient synthesis of 2-alkylpyridines using an alkylation/double decarboxylation strategy

We have discovered a novel route for synthesising 2-alkylpyridines by exploiting the decarboxylation of pyridyl malonate esters. Herein we report the synthesis of a number of examples and describe how the reaction was discovered.     

Allylation of 5-Methylfurfural Catalyzed by Phase-Transfer Reagents in Aqueous Media

Allylation of 5-methylfurfural with allyl halide and zinc was performed by using quaternary ammonium and phosphonium salts as phase-transfer catalysts. The phosphonium salt showed higher activity than the ammonium salt. Excellent yields were obtained with both catalysts.     

Allylation and cyanation of aza-aromatics activated by chloroformate and a catalytic amount of iodine

Allyltrimethylsilane and trimethylsilyl cyanide undergo smooth addition to N-acylated quinolines in the presence of a catalytic amount of iodine to afford 2-allyl- and 2-cyano-1,2-dihydroquinoline derivatives, respectively in good yields with high chemo- and regioselectivity. A variety of functional groups such as alkyl, alkoxy, halo, and nitro functionalities are tolerated under the reaction conditions.     

Allylation Reactions of Aromatic Aldehydes with Antimony in Aqueous Media Under Ultrasonic Irradiation

The allylation reactions of aromatic aldehydes with allyl bromide were carried out in 89–98% yield with Sb-H₂O-KF-CH₃OH under ultrasound irradiation at rt for 2.5 h. The reactions in the same system gave allylic alcohols in 30–69% yield with stirring for 24 h. The main advantages of the present procedure are shorter reaction time, better yield, and environmental friendliness.     

Rhodium-catalyzed alkylation of terephthaldialdimine with terminal alkenes via C-H bond activation

Terephthaldialdimine 1a reacted with alkenes to give 2,6-dialkylated products selectively in moderate to high isolated yields. In the case of terephthaldialdimine 1b having a substituent at site 2 in the phenyl ring, the alkylation takes place selectively at site 6 in the phenyl ring. In this alkylation, a meta-substituent affected the reactivity significantly because of the steric hindrance.     

Rhodium-catalyzed alkylation of aromatic azines with alkenes via C-H bond activation

The aromatic azines reacted with terminal alkenes under a rhodium catalyst [RhCl(coe)₂]₂ and Cy₃P to give the alkylated products with good to high isolated yields. The azines bearing H and o-CH₃, p-CH₃ and p-CH₃O groups have high reactivities, but m-CH₃O, p-Cl, p-F exhibit low reactivities.     

Efficient and Mild Iron-Catalyzed Direct Allylation of Benzyl Alcohols and Benzyl Halides with Allyltrimethylsilane

An efficient and mild iron-catalyzed direct allylation of benzyl alcohols and benzyl halides with allyltrimethylsilane has been developed. The present reaction would provide an excellent alternative to published methods because of its excellent yields, sustainable catalyst, and mild conditions.     

水溶液中金属铅诱发芳香醛的烯丙基化反应

超声辐射下,在Pb-THF-NH4C1-H2O体系中,烯丙基溴与一系列芳香醛室温反应4h,得62%～98%烯丙基化产物;而同样体系中搅拌20h,高烯丙基醇产率为63%～97%.     

Palladium catalyzed alkylation of indole via aliphatic C-H bond activation of tertiary amine

Alkylation of indoles has been achieved via Pd-catalyzed aliphatic C-H bond activation of tertiary amine coupling with indole followed by C-N bond cleavage and subsequent addition of indole. This method involves the migration of alkane chain from tertiary amine to indole.     

Cationic Zr-based metal-organic framework via post-synthetic alkylation for selective adsorption and separation of anionic dyes

Adsorption and separation of toxic organic dyes are of great importance in wastewater treatment and dye recycling. In this work, cationic metal-organic framework MIL-140C–2NMe⁺ with triangular hydrophobic channels was prepared in which methyl groups were added to the pyridyl sites of the ligand [2,2'-bipyridine]-5,5'-dicarboxylic acid (H₂bpydc) via post-synthetic alkylation reaction. MIL-140C–2NMe⁺ can be used as an efficient adsorbent for the selective adsorption and separation of anionic dyes in the aqueous mixture of cationic/anionic dyes. Specifically, the adsorption capacities of MIL-140C–2NMe⁺ for anionic methyl orange can reach 310 mg/g in 10 min. With a facile doctor-blading process, we have also polymerized the MIL-140C–2NMe⁺ nanocrystals and polyvinylidene fluoride (PVDF) polymer to fabricate a flexible and self-supporting mixed matrix membrane (MMM), which can selectively capture and separate the anionic organic dyes from the binary dye mixtures.     

Mild and Efficient Allylation of Indoles and Amides Using Amberlyst-15 as a Recyclable Heterogeneous Catalyst

A mild and efficient allylation of indoles and amides in the presence of a catalytic amount of Amberlyst-15 has been described in this context. The recyclable heterogeneous catalytic system is practical and facile for the synthesis of C- and N-allylated derivatives and would be of importance for the development of the accordingly functional complex molecules.     

Enantioselective alkylation of lactams and lactones via lithium enolate formation using a chiral tetradentate lithium amide in the presence of lithium bromide

Enantioselective alkylation of lactams and lactones can be realized up to 98% ee by deprotonation with a chiral tetradentate lithium amide (4b) in the presence of lithium bromide, and subsequent alkylation with active alkylating agents in non-chelating solvents.