A mild and general method for preparation of α-glycosyl chlorides

A mild and efficient chlorination method for production of glycosyl chlorides is first described which employs inexpensive trichlorotriazine (TCT) and DMF as a chlorination reagent and is compatible with typical acid-labile hydroxyl protecting functions. The scope and limitations, reaction mechanism and its application in the sequential glycosylations are discussed.     

Fluorous solvent as a new phase-screen medium between reagents and reactants in the bromination and chlorination of alcohols

[reaction: see text] A perfluorohexane layer regulates the rate of reagent transport in the bromination and chlorination of alcohols. A fluorous triphasic U-tube method is effective for lighter reagents; the thionyl chloride layer (yellow) vanishes, and the chlorides are obtained from the right top organic layer in the chlorination of alcohols.     

NMP-mediated chlorination of aliphatic alcohols with aryl sulfonyl chloride for the synthesis of alkyl chlorides

NMP-mediated chlorination of aliphatic alcohols has been developed for the synthesis of alkyl chlorides. This facile, efficient and practical approach used simple and readily available aryl sulfonyl chlorides as the chlorination reagent for the construction of C–Cl bond in good to excellent yields with mild conditions and broad substrate scope.     

Halogenation regioselective en serie aromatique—II: Chloration des naphtols et de leurs ethers a l'aide de reactifs mettant en jeu des interactions du type donneur-accepteur

The regiospecific chlorination of naphthols by hexachlorocyclohexadienones as selective chlorinating reagents is described. The selectivity attained is better than that which we have obtained with phenol derivatives and confirms the importance of the donor-acceptor interaction between the reagent and the naphthol during the chlorination.     

芳基偕二氯代化合物的新合成方法研究

以NCS为氯代试剂,在PPh3存在下,将芳香醛非常简便地转化为偕二氯代化合物,反应产率最高达到99%,该方法避免使用有毒的氯气作为氯代试剂,操作简单,反应条件温和,可在0℃下顺利进行.反应产物2f,2h,2i,2l,2m未见报道,其结构经1 H NMR,13 CNMR,IR和HRMS表征.     

DMSO-catalyzed chlorination of alcohols using N-phenylbenzimidoyl chloride

N-phenylbenzimidoyl chloride has been demonstrated as an efficient chlorination reagent catalyzed by dimethyl sulfoxide (DMSO) in conversion of alcohols to corresponding chlorides. The reaction conditions were mild, and most of the substrates gave satisfactory yields. The configuration inversion of the chlorination was proved using optically active phenyl alcohols. The amount of DMSO can be as low as 0.001 eq without reducing the efficiency of the chlorination. A plausible mechanism for the reaction was proposed and proved by experiments. The reaction is stereoselective and potentially chemoselective among primary benzyl alcohols, secondary benzyl alcohols, and unactivated aliphatic alcohols.     

A simple and highly effective oxidative chlorination protocol for the preparation of arenesulfonyl chlorides

2,4-Dichloro-5,5-dimethylhydantoin (DCDMH) was found to be a mild and efficient reagent for the direct oxidative conversion of sulfur compounds to the corresponding arenesulfonyl chlorides in good to excellent yields through oxidative chlorination. The method is suitable for many types of sulfur substrates (thiols, disulfides, and benzylic sulfides). The overall process is simple, practical, and it provides convenient access to a variety of aryl or heteroarylsulfonyl chlorides. The mild reaction conditions and the broad substrate scope render this method attractive and complementary to existing syntheses of aryl or heteroarylsulfonyl chlorides.     

Efficient Electrocatalysis for the Preparation of (Hetero)aryl Chlorides and Vinyl Chloride with 1,2‐Dichloroethane

Although the application of 1,2‐dichloroethane (DCE) as a chlorinating reagent in organic synthesis with the concomitant release of vinyl chloride as a useful byproduct is a fantastic idea, it still presents a tremendous challenge and has not yet been achieved because of the harsh dehydrochlorination conditions and the sluggish C?H chlorination process. Here we report a bifunctional electrocatalysis strategy for the catalytic dehydrochlorination of DCE at the cathode simultaneously with anodic oxidative aromatic chlorination using the released HCl as the chloride source for the efficient synthesis of value‐added (hetero)aryl chlorides. The mildness and practicality of the protocol was further demonstrated by the efficient late‐stage chlorination of bioactive molecules.     

Zinc hyperaccumulating plants as renewable resources for the chlorination process of alcohols

Abstract

Green Lucas reagent was prepared from Zinc hyperaccumulating plant, Thlaspi caerulescens. It is an effective and reusable reagent for the chlorination of tertiary, secondary, and primary alcohols. The results are the first use of contaminated biomass in organic synthesis and can constitute an encouragement for the economic development of phytoextraction and remediation programs for metal-bearing soils.     

Regiospecific Chlorination of Xylenes Using K-10 Montmorrillonite Clay

Regiospecific chlorination of xylenes has been developed by employing NCS as a reagent and K-10 montmorrillonite clay as a solid support.     

A practical and mild chlorination of fused heterocyclic N-oxides

Fused azine N-oxides were selectively chlorinated at C2 in moderate to excellent yields, employing Vilsmeier reagent as both the activating agent and the nucleophilic chloride source. Remarkable features of the method include simple operation, mild reaction conditions, a wide substrate scope, and the use of only stoichiometric amount of POCl_3. The potential extension of this method to a one-pot oxidation/chlorination sequence that obviates the need for isolation of the N-oxide intermediates is also validated.     

Process Parameters of Oxidative Chlorination of Benzene with the Participation of Nitrogen(IV) Oxide

The efficiency of replacing oxygen with nitrogen(IV) oxide in oxidative chlorination of benzene was studied. The optimal process parameters: temperature, time of contact, and relative content of reagent, were determined.     

Pd-catalyzed regioselective C-H chlorination of disubstituted 1,2,3-triazoles

This paper mainly studied Pd-catalyzed regioselective chlorination of disubstituted 1,2,3-triazoles directed by the 1,2,3-triazole ring. A series of regioselective chlorinated products were synthesized in 47–86% yields using Pd(OAc)₂ as a catalyst and CuCl₂ as a chlorinated reagent. This method provides a new mean for the synthesis of 1,2,3-triazole halides which combines the formation of C-X bond with C-H activation.     

Metal-free halogenation of arylboronate with N-halosuccinimide

Efficient bromination and chlorination of aryl pinacol boronates were accomplished without the addition of metal reagent. The reaction proceeded efficiently with electron-rich arylboronates or heteroarylboronates in DMF or acetonitrile, to afford mono-, di-, or trihalogenated aryl pinacol boronates.     

Halogenation regioselective en serie aromatique—I: Chloration des phenols et de leurs ethers a l'aide de reactifs mettant en jeu des interactions donneur-accepteur

An efficient regiospecific route for the chlorination of phenol involving hexachlorocyclohexadienones is described. The selectivity is attained by using a reagent tailored in such a way that it is able to participate in charge transfer interactions and hydrogen bonding with the substrate. This recognition between substrate (phenol) and 2, 3, 4, 4, 5, 6-hexachlorocyclohexa 2, 5-dien 1-one 1 which we have called “réactif p” allows the chlorination of phenol in the para position. The use of 2, 3, 4, 5, 6, 6-hexachlorocyclohexa 2,4-dien-1 one 2 we have called “reactif o” permits the chlorination in the ortho position. These two reagents are stable and inexpensive materials, synthetized from pentachlorophenol and chlorine. The chlorination of anisole with these two reagents, gives solely the parachloro derivative, under steric control.     

Direct and enantioselective organocatalytic alpha-chlorination of aldehydes

The first direct enantioselective catalytic alpha-chlorination of aldehydes has been accomplished. The use of enamine catalysis has provided a new organocatalytic strategy for the enantioselective chlorination of aldehydes to generate alpha-chloro aldehydes, an important chiral synthon for chemical and medicinal agent synthesis. The use of imidazolidinone 3 as the asymmetric catalyst has been found to mediate the halogenation of a large variety of aldehyde substrates with the perchlorinated quinone 1 serving as the electrophilic chlorinating reagent. A diverse spectrum of aldehyde substrates can also be accommodated in this new organocatalytic transformation. The capacity of catalyst 3 to override the inherent bias of resident stereogenicity in the chlorination of enantiopure beta-chiral aldehydes is also described. Catalyst quantities of 5 mol % were generally employed in this study.     

Rhodium(III)-catalyzed intermolecular direct amination of aromatic C-H bonds with N-chloroamines

A Rh(III)-catalyzed direct aromatic C-H amination is achieved using N-chloroamines as a reagent. Furthermore, we also developed a one-pot amination protocol involving in situ chlorination of the secondary amines. The catalytic amination operates at mild conditions with excellent functional group tolerance and regioselectivity.     

The oxidation of aldehydes to acids with calcium hypochlorite [Ca(OCl)2]

Calcium hypochlorite is an efficient reagent for the oxidation of aldehydes to the corresponding acids. Reactions are carried out at ambient temperature in aqueous acetonitrile-acetic acid solution. Aliphatic aldehydes and aromatic aldehydes with electron withdrawing groups afford good to excellent yields. Nuclear chlorination is the preferred reaction in aromatic aldehydes with electron donating groups.     

Determination of dichloroacetic acid and trichloroacetic acid by liquid-liquid extraction and ion chromatography

An extraction technique using MTBE (methyl tert. butyl ether) and reagent water in combination with ion chromatography and conductivity determination was developed to quantify dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) concentrations in raw water after chlorination. The detection limit of the method was 0.45 and 1.50 microg/L for DCAA and TCAA, respectively. Mean values of recovery ranged from 90 to 96% for DCAA and 95 to 108% for TCAA. The evaluation of recovery and precision of the method indicates that the performance characteristics are comparable with gas chromatographic (GC) methods reported in literature. In addition, the procedure is simple, fast, and does not need any derivatization step. Application of the analytical method to the determination of DCAA and TCAA in real samples is shown.     

Determination of dichloroacetic acid and trichloroacetic acid by liquid-liquid extraction and ion chromatography

An extraction technique using MTBE (methyl tert. butyl ether) and reagent water in combination with ion chromatography and conductivity determination was developed to quantify dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) concentrations in raw water after chlorination. The detection limit of the method was 0.45 and 1.50 μg/L for DCAA and TCAA, respectively. Mean values of recovery ranged from 90 to 96% for DCAA and 95 to 108% for TCAA. The evaluation of recovery and precision of the method indicates that the performance characteristics are comparable with gas chromatographic (GC) methods reported in literature. In addition, the procedure is simple, fast, and does not need any derivatization step. Application of the analytical method to the determination of DCAA and TCAA in real samples is shown.