In recent years, multicomponent reactions with inorganic and organic sulfur compounds as one of reactants have achieved a remarkable development. In this review, we summarize recent advances in the multicomponent reactions involving sulfur components, which include elemental sulfur, sodium metabisulfite, sodium hyposulfite, potassium pyrosulfite, DABSO, sodium sulfide, thiocyanate, sulfur dioxide, carbon disulfide and other divalent, tetravalent and hexavalent organosulfur compounds.

In recent years, sulfenate anions as key intermediates in enantioselective synthesis have attracted considerable attention. Typically, development of novel synthetic methods to generate sulfenate anions allows for the preparation of various enantiopure sulfoxides, which are prevalently used as auxiliaries, ligands, organocatalysts, and biologically active compounds. This review presents the in situ preparation methods and the recent applications of sulfenate anions in catalytic asymmetric synthesis of chiral sulfoxides.

A synthetic protocol of dibenzyl thioethers and dibenzyl disulfides via S N 2 nucleophilic substitution of quaternary ammonium salts and sodium sulfide nonahydrate and disodium disulfide under mild condition is described. In particular, if quaternary ammonium salts synthesized from enantiomerically enriched amines are adopted, highly enantioenriched dibenzyl thioethers (92-95% ee) with reverse configurations to their enantioenriched quaternary ammonium salts are obtained.Thioethers and organic disulfides extensively exist in glycoproteins, [1] fungal metabolites [2] and various plants of the genus Allium, [3] and exhibit some bioactivities. They have been widely used in medicinal chemistry, [1][2][3][4][5] chiral ligands/catalysts and drugs. [6] Dibenzyl disulfides containing S-S bond, which are commonly found in anti-cancer drugs. [2,4] A number of chiral thioether catalysts and ligands, such as A, B, C and D in Figure 1, have been used in a series of catalytically asymmetric reactions with excellent enantioselectivities. [6] Montelukast [7] and Cardizem [8] are typical chiral thioether medicines (Figure 1), which belong to the best-selling pharmaceutical products. Moreover, more than one-fifth of the top 200 most-prescribed drugs belong to sulfur-containing compounds, while thioethers represent the third most exemplified constituent of the sulfurcontaining drugs. [9] Chiral thioethers are converted into chiral sulfone compounds under the action of oxidant, which further broadens the application of chiral thioether compounds. [10] In the past decades, there are many methods for the preparation of thioethers, [11][12] but there are only a few approaches that prepare chiral thioethers from amine derivatives [13][14] via CÀ N cleavages. In particular, the exploration of organosulfur reagents for the construction of carbon-sulfur bonds is of widespread interest. [15,16] Tian and co-workers reported that stereospecifific nucleophilic substitution of higher reactive enantioenriched quaternary ammonium salts with a Nphenyl group from enantioenriched tertiary benzylic amines via in situ activation with benzyne (Scheme 1, eqn. (a)); [17] it is no reaction for less reactive benzylic quaternary ammonium salts with a N,N,N-trimethyl group. [17] Our group discovered that less reactive enantioenriched quaternary ammonium salts with a N,N,N-trimethyl group from enantioenriched tertiary benzylic amines via in situ activation with methyl triflate may be transformed into chiral benzylic thioethers via copper(I)-catalyzed CÀ S coupling reaction (Scheme 1, eqn. (b)). [18] Later, we further[a] Q. Tang, F.

<abstract> <p>Amines are abundant in natural product chemistry and are readily available chemical raw materials. The C-N bonds of amines are difficult to break due to the large C-N bond energy. In recent years, chemists have developed a variety of activation methods for amino groups of amines. Among these reported methods, to convert amines into quaternary ammonium salts is preferred, for quaternary ammonium salts are readily available and stable. In recent years, great progress has been achieved in the study of transition metal-catalyzed construction of various C-X bonds involving aromatic amines and benzyl amines-derived quaternary ammonium salts by cleavage of C-N bonds. This review describes the transition metal-catalyzed reaction of quaternary ammonium salts to construct C-X bonds by cleavage of C-N bond. Moreover, if chiral benzylamines-derived quaternary ammonium salts are used, a variety of highly enantiomeric pure chiral organic compounds can also be obtained. The chirality of quaternary ammonium salts remained good in the products and all reactions underwent S_N2-type configuration inversion.</p> </abstract>

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