Direct reduction of alcohols, to avoid tedious reaction steps, has drawn broad attention. However, the transformation was mainly catalyzed by transition metals or Lewis acids. Developing a metal-free and recyclable catalytic system is still a challenging task from the viewpoint of green chemistry. Herein, pyrrolidine-based ionic liquids as metal-free and recyclable catalysts for direct reduction of aromatic allylic alcohol were developed using p-methylbenzyl alcohol as the reducing agent in dimethyl carbonate (DMC). DMC not only acted as the green solvent but also could stabilize the reaction intermediates and improve the reactivities. Aromatic allylic alcohols with electron-donating or -withdrawing groups could provide up to 92% yield. The gram-scale experiment was performed smoothly, and the recycle experiment of the ionic liquids could be achieved through simple steps, which was significant for environmental protection and efficient utilization of resources. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy proved that ionic liquids interacted with the substrates and the reducing agent by forming multiple hydrogen bonding interactions. Kinetic isotope effect (KIE) experiments (k H /k D = 2.27) indicated that the C−H bond cleavage might be a rate-determining step, and deuterium-labeled results demonstrated that the hydrogen of the product was derived from the benzylic H of p-methylbenzyl alcohol. Meanwhile, the experiments of two preprepared ether intermediates as the substrates showed that they may be involved during the reaction, and a possible mechanism containing intermediates, hydrogen transfer, and hydrogen bonding effects was proposed.

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Allylic amines are valuable and functional building blocks. Direct N-allylation of pyrazole and its derivatives as an atom economic strategy to provide allylic amines has been achieved only using commercial Bu 4 NHSO 4 as the metal-free catalyst and water as the solvent without any additives. 11-93% isolated yields were obtained for the N-allylation of pyrazole and its derivatives with allylic alcohols. Bu 4 NHSO 4 could be reused for six times by simple extraction nearly without loss of catalytic activity and was also suitable for a gram-scale production. The reaction of allylic ether and pyrazole did not occur to give the desired product indicated that allylic ether was not the active intermediate in the pathway. Density functional theory (DFT) calculations reveal that there are hydrogen bonding effects among substrates, solvent and catalyst, especially the one formed between allylic alcohol and H 2 O. Control experiments in different protic solvents further demonstrate the intermolecular hydrogen bonding of allylic alcohol and water.

Thioethers as important building blocks have been usually found in organic synthesis. Herein, a series of long chained acid‐functionalized ionic liquids derived from pyrrolidine were applied for the thiolation of alcohols to synthesize different compounds containing thioether structures. This kind of ionic liquids exhibited higher efficiency than general ionic liquids based on imidazole, providing up to 99 % yield with [BsCtP][OTf] as the catalyst at room temperature for 0.25 h. The results indicated that the activities of the ionic liquids have relationship with the side chain length of ionic liquids based on pyrrolidine, anions and cations. The catalytic system had wide substrate scope and was applicable for the reaction of aromatic primary and secondary alcohols and thiols including aliphatic and aromatic thiols, benzothiazole‐2‐thiols and benzooxazole‐2‐thiols. Besides, there was no obvious change in activity of the catalyst after six runs. Thus, the catalytic system exhibited good recyclability. Additionally, carbocations should be the key intermediate and several functionalized groups of the ionic liquids have synergetic effect for the thiolation.

Direct metal-free deoxygenation of highly active allylic alcohols catalyzed by a Brønsted acid was achieved, which avoids tedious reaction steps and eliminates metal contamination. By examining a series of Brønsted...

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One of the ultimate goals in organic synthesis is to develop metal‐free, efficient and easily separable catalytic system for atom economic organic reactions in an environmental solvent. Direct substitution reaction of alcohols and hydrocarbon compounds is a significant and atom economic method for C−C bond formation. Herein, a metal‐free and efficient catalytic system including recyclable pyridine‐based ionic liquids with multiple active sites as the catalyst and dimethyl carbonate as the environmentally friendly solvent was developed for atom economic C3 substitution of 4‐hydroxycoumarins with alcohols. Primary aromatic alcohols, secondary aliphatic and aromatic alcohols were suitable for the reaction, providing up to 99 % yield. The catalytic system could be easily scaled up to gram‐scale with nearly quantitative yield. Coumatetralyl as commercial rodenticide could be prepared directly from commercially available 4‐hydroxycoumarin and 1,2,3,4‐tetrahydronaphthalen‐1‐ol. Racemic product derived from the reaction of (R)‐1‐phenylethanol and 4‐hydroxycoumarin indicated the reaction was achieved through an SN1 pathway. The comparison of the activities and acidities of the ionic liquids demonstrated that there was no directly relationship between them. Control experiments showed that the reaction probably proceeded via carbocation, ether intermediate and synergistically promoted effect of hydrogen bonding between the ionic liquid with multi‐active sites and substrates.

We have established H3PW12O40·xH2O catalyzed O-alkylation of oximes with alcohols in DMC, and investigated the corresponding mechanism.