One-pot synthesis of unsymmetrical disulfides using 1-chlorobenzotriazole as oxidant: Interception of the sulfenyl chloride intermediate

A high-yielding and low temperature one-pot procedure is described for unsymmetrical disulfide synthesis from two different thiols using 1-chlorobenzotriazole (BtCl) as oxidant. The mechanism of the coupling involves in situ trapping of the sulfenyl chloride intermediate R¹SCl by nucleophilic benzotriazole (BtH) to form R¹SBt, which protects R¹SCl from forming the homodimer R¹SSR¹. The methodology is applicable to all types of thiol (aliphatic, aromatic, heteroaromatic), with a variation developed for aliphatic-aliphatic couplings. Differentially N-protected cysteines couple to afford the unsymmetrical cystine derivatives in high yield (90%), which serves as a model for the one-pot intermolecular coupling of cysteine-containing peptides to form peptide disulfide heterodimers. Minimal exchange in aromatic-aromatic disulfide synthesis is noted on account of the mild conditions.     

Inexpensive, one-pot synthesis of unsymmetrical disulfides using 1-chlorobenzotriazole

A new synthesis of unsymmetrical disulfides is described. The reaction of a thiol R1SH with 1-chlorobenzotriazole (BtCl) at -78 degrees C in DCM affords a high-yielding conversion to R1SBt without appreciable formation of the symmetrical disulfide R1SSR1. R1SBt is then reacted with R2SH to form the unsymmetrical disulfide in a one-pot sequence with green character that avoids the use of toxic and harsh oxidizing agents. The methodology has been developed for synthesis of various types of disulfides.     

Iodine-catalyzed one-pot synthesis of unsymmetrical meso-substituted porphyrins

The wide range use of 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin is well established, but its synthesis requires two steps and is not very practical. This article describes an iodine-catalyzed one-pot synthesis of this unsymmetrical porphyrin that uses commercial reagents and reactants as such, without prior distillation. Unsymmetrical mono functionalized porphyrins with various functional groups have also been obtained to validate this method. The influence of electronic effects of functional groups (donor or acceptor) has also been studied.     

A traceless, one-pot preparation of unsymmetric disulfides from symmetric disulfides through a repeated process involving sulfenic acid and thiosulfinate intermediates

A variable group of unsymmetric disulfides was prepared under mild reaction conditions and in high yields through the reaction of symmetric disulfides with sulfuryl chloride followed by treatment with thiols in the presence of water.     

A convenient one-pot preparation of glycosyl bromides as well as glycosyl acetates from benzyl glycosides using N-bromosuccinimide.

Some conversions of benzyl glycoside using NBS were examined and one-pot preparation of glycosyl acetates and bromides were developed. An efficient O-debenzylation at non-anomeric position was also observed.     

Facile direct synthesis of unsymmetrical ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines using DABAL-Me3

A practical synthetic method for the direct synthesis of unsymmetrically substituted ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines is described. In this study, efficient direct conversion of the Alloc-, Cbz-, and Boc-carbamate compounds to ureas was achieved in the presence of DABAL-Me₃, an air stable and easily handled reagent. Using this reaction method, both protected aromatic and aliphatic amines were successfully transformed into various trisubstituted and tetrasubstituted ureas with high yields without side product. Our findings offer promising guidelines for direct preparation of useful ureas from N-Alloc-, N-Cbz-, and N-Boc-carbamates.     

3-甲基-1-磺酸咪唑硫酸氢盐催化剂用于四组分一锅法合成不对称聚羟基喹啉衍生物(英文)

3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an efficient, halogen-free,and reusable Brnsted acidic ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl- hexahydro-trimehtyl-5-oxoquinoline-3-carboxylates via the one-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantage of being clean and simple, as well as providing the desired product in high yield over a short reaction time. Furthermore, the catalyst could be recycled and reused four times without any discernible reduction in activity.     

A novel dual-nano assisted synthesis of symmetrical disulfides from aryl/alkyl halides

Here, we have reported a novel approach towards dual-nano assisted synthesis of disulfides from coupling of alkyl/aryl halides and sulfur nanoparticles. The indium oxide nanoparticles as catalyst expedite the conversion and sulfur nanoparticle notably enhances the miscibility, providing a faster, high yielding and cost-effective process in ethanol-water system. The method has synthetic advantages in terms of mild reaction framework, catalyst regeneration, and absence of any sulfide or polysulfide linkage as by-product leading to a column free synthesis. A variety of alkyl, aryl and heteroaryl symmetrical disulfides are obtained in good to excellent yields up to exceeding 98%.     

N-Trifluoroacetyl arenesulfenamides, effective precursors for synthesis of unsymmetrical disulfides and sulfenamides

N-Trifluoroacetyl arenesulfenamides (3) were effective precursors for the synthesis of unsymmetrical disulfides (4) and sulfenamides (5). Reactions of 3 with a variety of aromatic thiols at room temperature were generally complete within 5 min and gave unsymmetrical diaryl disulfides in high yields. Aralkyl disulfides were isolated in high yields from the reaction of 3 with aliphatic thiols. The nucleophilic substitution reactions of 3 with amines proceeded smoothly and provided N-substituted sulfenamides in good to excellent yields.     

Multicomponent one-pot solvent-free synthesis of functionalized unsymmetrical dihydro-1H-indeno[1,2-b]pyridines

A simple and efficient synthesis of 4-aryl-4,5-dihydro-1H-indeno[1,2-b]pyridine derivatives has been achieved via a four-component cyclocondensation of 1,3-indanedione, aromatic aldehydes, β-ketoesters and ammonium acetate in one-pot in the absence of catalyst and solvent at room temperature on grinding. The present approach offers several advantages such as shorter reaction times, higher yields, low cost, simple work-up and easy purification.     

Determination of pentoxifylline in pharmaceutical formulations using iodine as oxidizing agent

Simple, selective and sensitive spectrophotometric methods are described for the determination of pentoxifylline, based on the haloform reaction with a known and excess of standard iodine solution under alkaline conditions. The excess of iodine is determined at pH 3.0 with metol–isoniazid (λ_max=620 nm; method A) or wool fast blue BL (λ_max=540 nm, method B). All the variables have been optimised and the reaction mechanisms presented. Regression analysis of Beer's law plots showed good correlation in the concentration ranges 4.0–24.0 and 0.4–2.4 mg ml⁻¹ for methods A and B respectively. No interferences were observed from excipients and the validity of the methods was tested by analysing pharmaceutical formulations. Recoveries were 99.0–100.0%. The concentration measurements were reproducible within a relative standard deviation of 1.0%.     

A high yielding, one-pot synthesis of O,S-dialkyl dithiocarbonates from alcohols using Mitsunobu’s reagent

A novel Mitsunobu-based protocol has been developed for the synthesis of O,S-dialkyl dithiocarbonates from a variety of primary, secondary and tertiary alcohols using carbon disulfide, in good to excellent yields. This protocol is mild and efficient compared to other reported methods.     

A green synthesis of unsymmetrical triarylmethanes via indium (III) triflate catalyzed Friedel Crafts alkylation of o-hydroxy bisbenzylic alcohols under solvent free conditions

Using indium (III) triflate as a mild Lewis acid catalyst, the Friedel Crafts alkylation of o-hydroxy bisbenzylic alcohols with aromatic/heteroaromatic arenes under solvent free conditions was achieved to give the corresponding unsymmetrical triarylmethanes in high yields (up to 80% yield). Calculation of the different green metrics for the above reaction revealed it to have high atom economy (94–96%), high reaction mass efficiency (66–77%) and high carbon efficiency (70–80%). The Lewis acid was found to be air and moisture tolerant. The protocol was found to be operationally simple and can be carried out in an “open-flask” leaving behind water as the sole by product. Gratifyingly the Lewis acid catalyst could be recycled and reused up to 5 catalytic cycles without compromising much on the yield thus further highlighting the importance of the protocol.     

Microdetermination of naturally occurring nodososide from Cassia nodosa, using chlorauric acid as oxidizing agent in alkaline medium

Nodososide, isolated from the flowers of Cassia nodosa, has been quantitatively determined by oxidizing with chlorauric acid in large excess of alkali. The oxidation reaction between nodososide and chlorauric acid is preceded by alkaline hydrolysis and is completed at 48 equivalence, resulting in the formation of sodium formate and acetate as main products. Maximum error observed was 1.4%. The method is accurate and gives reproducible results.     

A three-step total synthesis of goniothalesdiol A using a one-pot Sharpless epoxidation/regioselective epoxide ring-opening

Using a one-pot Sharpless asymmetric epoxidation/regioselective epoxide ring-opening as a key step, the protecting-group-free total synthesis of goniothalesdiol A was accomplished in only three steps starting from commercially available trans-cinnamaldehyde in 55.1% overall yield. In 6 previously reported total syntheses, 6–11 steps were required.     

A one-pot synthesis of 1,2,4,5-tetraarylimidazoles using molecular iodine as an efficient catalyst

Molecular iodine is a cheap, nontoxic catalyst, which acts as an efficient catalyst for the synthesis of 1,2,4,5-tetraarylimidazoles using benzoin, an aromatic aldehyde and an amine in the presence of ammonium acetate. The advantage of this method is the direct use of benzoin, which is transformed into benzil in situ and condenses further to generate the imidazole in a one-pot sequence.     

Four-component one-pot synthesis of a branched manno-pentasaccharide: tert-butyldiphenylsilyl ether as an in situ removable carbohydrate-protecting group

A branched mannose-pentasaccharide was synthesized in a convergent one-pot sequence involving chemo- and regioselective glycosylations of suitable acceptors and in situ removal of tert-butyldiphenylsilyl group. The process demonstrated that a combination of TMSOTf and TfOH can be used as an effective reagent for the fast and selective in situ de-protection of tert-butyldiphenylsilyl group, and also serve as part of the promoter system for the subsequent glycosylation reaction.     

Synthesis of ferrierite-type zeolite by microwave method using ethylenediamine as an organic structure-directing agent

A new method for the synthesis of ferrierite-type zeolite has been developed using microwave irradiation in the presence of structure-directing agents (templates). The physicochemical characteristics of the synthesized zeolites were investigated by X-ray diffraction analysis, low-temperature nitrogen adsorption–desorption and SEM-EDX. When comparing the synthesis products, it was found that microwave irradiation significantly reduces the crystallization time of the synthesized zeolites compared to traditional hydrothermal treatment     

One-pot synthesis of aryl alkyl thioethers and diaryl disulfides using carbon disulfide as a sulfur surrogate in the presence of diethylamine catalyzed by copper(I) iodide in polyethylene glycol (PEG200)

A copper catalyzed one-pot protocol for the preparation of aryl alkyl thioethers and diaryl disulfides using carbon disulfide as the sulfur source and diethylamine in polyethylene glycol (PEG200) is described.     

A green one-pot multicomponent synthesis of 4H-pyrans and polysubstituted aniline derivatives of biological, pharmacological, and optical applications using silica nanoparticles as reusable catalyst

A one-pot practical, efficient, and environmentally benign multicomponent synthesis of 4H-pyrans and polysubstituted aniline derivatives of biological, pharmacological, and optical applications has been developed using a very mild, neutral, and reusable silica nanoparticles as catalyst. The 4H-pyran derivatives were synthesized by a three component reaction of an aldehyde, malononitrile, and 5,5-dimethyl-1,3-cyclohexanedione or ethyl acetoacetate at room temperature or refluxing in ethanol. Alternatively, polysubstituted anilines were synthesized via a four component reaction of an aldehyde, a ketone, and two equivalents of malononitrile in ethanol.