Efficient synthesis of bis(indolyl) methanes catalyzed by(PhCH_2PPh_3)^+Br_3^- under solvent-free conditions

Benzyltriphenylphosphonium tribromide（BTPTB） has been applied as an efficient catalyst for the preparation of bis（indolyl）-methanes （BIMs） via electrophilic substitution of indoles with aldehydes in the absence of solvent.

V(HSO_4)_3 catalyzed chemoselectivity acetylation of alcohols and phenols in solution and under solvent-free conditions

A variety of alcohols and phenols are efficiently acetylated with acetic anhydride in the presence of a catalytic amount of V（HSO4）3 in solution and under solvent free conditions. Mild reaction conditions, high yields of the products, easy procedure and selective acetylation of alcohols and phenols in the presence of amines and thiols are the main advantages of this procedure.

Strontium chloride-catalyzed one-pot synthesis of 4(3H)-quinazolinones under solvent-free conditions

Strontium chloride was used as an efficient and recyclable catalyst in one-pot condensation of anthranilic acid, ortho esters and amines leading to the formation of 4（3H）-quinazolinone derivatives in good yields at room temperature under solvent-free conditions.

Reductive amination of aldehydes and ketones using sodium borohydride in the presence of silica chloride under solvent-free conditions

A simple and convenient procedure for the preparation of amines from aldehydes and ketones with sodium borohydride activated by silica chloride as a catalyst under solvent-free conditions is described.A variety of aliphatic and aromatic aldehydes,ketones and amines when mixed with NaBH;/silica chloride at room temperature,afforded excellent yield of the corresponding amines.

Yb(OTf)_3-catalyzed synthesis of pyrroles under solvent-free conditions

A Yb（OTf）3-catalyzed approach for the synthesis of pyrroles under solvent-free conditions was achieved, which could afford the desired products with yields ranged from moderate to excellent.

Highly Efficient and Recyclable Catalyst HBF_4·SiO_2 Catalyzed Synthesis of β-Enamino Compounds Under Solvent-free Conditions

Fluoroboric acid adsorbed on silica-gel（HBF4·SiO2） has been found to be an extremely efficient and recyclable catalyst for the preparation of β-enaminones and β-enamino esters under solvent-free conditions.

Highly efficient synthesis of β-amino esters via Mannich-type reaction under solvent-free conditions using ZnCl_2 catalyst

β-Amino esters were synthesized via ZnCl2-catalyzed Mannich-type reaction of imines and malonate esters under solvent-free conditions in 6 min. The β-amino ester was converted into the corresponding aspartic acid derivatives.

Silica supported sodium hydrogen sulfate(NaHSO_4/SiO_2):A mild and efficient reusable catalyst for the synthesis of aryl-14-H-dibenzo[a,j]xanthenes under solvent-free conditions

A simple and efficient procedure for the preparation of aryl- 14-H-dibenzo [aj]xanthenes by a one-pot condensation reaction of 2-naphthol and aryl aldehydes, in the presence of silica supported sodium hydrogen sulfate （NaHSO4/SiO2） as a catalyst and in the absence of solvent has been developed. The present method offers several advantages such as excellent yields, short reaction time （10-30min）, mild condition, simple work-up, and the use of a cheap and environmentally friendly catalyst with remarkable reusability.

One-pot synthesis of tri- and tetra-substituted imidazoles using sodium dihydrogen phosphate under solvent-free conditions

Sodium dihydrogen phosphate （NaH2PO4） efficiently catalyzes the condensation reaction of benzil, aldehydes, amines and ammonium acetate in a four-component reaction under solvent-free conditions. The reaction proceeds rapidly and affords the corresponding tetra-substituted imidazoles in high yields. Also an efficient route was developed for the synthesis of tri-substituted imidazoles from condensation of benzil, aldehydes and ammonium acetate using NaH2PO4.

Efficient one-pot synthesis of 14-substituted-14H-dibenzo[a,j]xanthenes using boric acid under solvent-free conditions

Boric acid efficiently catalysed the one-pot reaction of alkyl or aryl aldehydes with 2-naphthol to afford the corresponding 14- alkyl-or aryl-14H-dibenzo[a,j]xanthenes in good yields under solvent-free conditions.

An Improved Synthesis of Azines under Solvent-Free Conditions

A new convenient and environmentally benign procedure for synthesis of azines from hydrazme sulfate with several aromatic aldehydes coupled with grinding is studied. This reaction is carried out under solvent-free conditions and in absence of catalyst to afford high yields of relevant azines.

A Simple and Efficient Procedure for a 2-Pyridones Synthesis under Solvent-Free Conditions

A new series of 3-cyano-2-pyridones derivatives have been prepared by reaction of enaminonitriles with pri-mary amine under solvent free condition. This procedure have the advantage of high yields and being environ-mentally-friendly.

Glycerol-Based Carbon-SO₃H Catalyzed Benign Synthetic Protocol for the Acetylation of Alcohols, Phenols and Amines under Solvent-Free Conditions

A simple and efficient solvent-free method was developed for the acetylation of alcohols, phenols and amines in excellent yields employing glycerol-based sulfonic acid (-SO3H) functionalized carbon catalyst under environmentally benign reaction conditions. The salient features of this protocol are the short reaction time, ease of product isolation and reusability of the carbon catalyst.

FeCl₃Catalyzed One Pot Synthesis of 1-Substituted 1H-1,2,3,4-Tetrazoles under Solvent-Free Conditions

An efficient procedure for the preparation of 1-substituted-1H-1,2,3,4-tetrazoles via a three-component condensation of triethyl orthoformate, amine, and trimethylsilyl azide using inexpensive and environment-friendly FeCl3 as catalyst under solvent-free conditions has been reported. The reaction generates the corresponding 1-substituted tetrazole in excellent yields.

Nanostructured bimetallic Zn/Co in N-doped carbon as an efficient catalyst for the alcohol dehydrogenation to carboxylic acids under solvent-free conditions

The catalytic alcohol dehydrogenation to carboxylic acids has been demonstrated as an atom-economic and environmental-friendly synthetic method.However,the reported catalysts either require relatively complicated synthesis or exhibit high activity only in the presence of a solvent.Therefore,it is still in high demand to obtain catalysts that feature facile synthesis and perform well even without any solvent.Herein,a series of nanostructured bimetallic Zn/Co species embedded in N-doped hierarchical porous carbon were fabricated in a facile and green manner.More significantly,the best-performing material(Zn/Co@NC-800)was identified as the first heterogeneous catalyst to enable this transformation under solvent-free conditions.Moreover,the as-prepared composites were comprehensively investigated to de-termine their structural and morphological properties,which rationalized the superiority of Zn/Co@NC-800 over the other synthesized materials.Further studies signified that Co sites(both Co^(0)and Co^(2+))and N species(mainly pyridinic N)were probably involved in this process,functioning as the Lewis acid site and basic site,respectively.Hopefully,this study could provide a simple and sustainable method for carboxylic acid synthesis.

One-pot synthesis of various xanthene derivatives using ionic liquid1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient and reusable catalyst under solvent-free conditions

In this study, 1,3-disulfonic acid imidazolium hydrogen sulfate （DSIMHS） is used as an efficient and reusable ionic liquid for the green, mild, and efficient synthesis of xanthenes under solvent-free conditions. Simple and easy work-up, low cost, green process, short reaction times and excellent yields of the products are the advantages of this procedure. Further, the catalyst can be recycled and reused at least for four times without a noticeably decrease in its catalytic activity.

Highly efficient and easy synthesis of 2,4,6-triarylpyridines catalyzed by pentafluorophenylammonium triflate(PFPAT) as a new recyclable solid acid catalyst in solvent-free conditions

Pentafluorophenylammonium triflate（PFPAT） was found to be a highly efficient catalyst for the preparation of 2,4,6- triarylpyridines from the reaction of acetophenone derivatives,aromatic aldehydes and ammonium acetate.Present methodology offers several advantages,such as short reaction time,high yields,simple procedure with an easy work-up and the absence of any volatile and hazardous organic solvent.In addition,this catalytic system can act as an active,inexpensive,metal-free,recoverable and recyclable catalyst.

A VERSATILE AND REGIOSELECTIVE SYNTHESIS OF VICINAL AZIDOALCOHOLS USING CROSS-LINKED POLY(4-VINYLPYRIDINE) SUPPORTED AZIDE ION UNDER SOLVENT-FREE CONDITIONS

A new polymeric reagent, cross-linked poly（4-vinylpyridine） supported azide ion, [P4-VP]N3, was introduced as polymeric reagents for efficient and regioselective conversion of epoxides to azidohydrins in the presence of cross-linked poly（4-vinylpyridine） supported sulfuric acid, [P4-VP]H2SO4, as a solid proton source and as catalyst under solvent-free conditions. The advantages of this polymeric reagent over some of those reported in the literature are easy work-up procedure and regeneration of the reagent.

Environmental Friendly Synthesis of Novel Isatin Ketal and Isatin Schiff Base Derivatives Using Michael Addition Reaction under Solvent-Free Conditions

An efficient and simple procedure for the synthesis of novel isatin derivatives is described. Michael addition of aniline Schiff bases of isatin or p-toluidine Schiff bases of isatin to fumaric esters affords the Michael adduct com- pounds in good to high yields in the presence of K2CO3 and tetrabutylammonium bromide （TBAB） under sol- vent-free conditions. Repeating of this reaction about spiro[l,3-dioxolane-2,3＇-indol]-2＇（l＇H）-one, as a Michael do- nor, in the presence of 1,4-diazabicyclo[2.2.2]octane （DABCO） gives Michael adducts in remarkable yields under the same conditions.