Dithiocarboxylic esters, and

Thioesters of the type RSC(=S)R (a dithiocarboxylic ester) and RSC(C=0)R (a thiocarboxylic ester) can be generated by reaction of carboxylic acids with thiols. 

Dithiocarboxylate esters and dithiolactones are analogously available from thioloesters or thiololactones and LR. Open-chain arylphenyldithioacetates, 1-arylethyl arenedithioates, and also ethyl 7V-Boc-/3-aminopropanedithioate (51) have been... 

The thioacylation of NH groups by dithiocarboxylic esters and their salts, as well as by thionocarboxylic esters, is dealt with in Section 5 of this chapter. Diphenylcyclopropenethione reacts with amines to give the cycloadducts (91), which are rearranged to the thioamides (92) when heated in benzene. Thioamides RNHC(S)CHXY are obtained from compounds with active methylene groups by reaction with A-aryldithiocarbamic acid esters, e.g. MeSC(S)NHPh, thiocarbamoyl chlorides, or C-sulphonylthioformamides,... 

Although deprotonation of simple 1,3-dithiolanes at the 2 position is usually accompanied by cycloreversion to the alkene and dithiocarboxylate, this does not occur for the 2-ethoxycarbonyl compound 55. The anion of this is readily generated with LDA and undergoes conjugate addition to a,(3-unsaturated ketones, esters, and lactones to give, after deprotection, the a,8-diketoester products 56 (73TL2599). In this transformation 55 therefore acts as an equivalent of Et02C-C(0) . 

Dithiocarboxylic acids, their esters and metal dithiocarboxylates. E. Jansons, Russ. Chem. Rev. (Engl. Transl.), 1976,45,1035-1051 (350). 

Thione-S-oxides react regiospecifically with allyl and benzylsilanes in the presence of a stoichiometric amount of tetra-n-butylammonium fluoride to produce allyl and benzyl sulphoxides [8], cf. the analogous fluoride initiated reaction of thio-ketones and dithiocarboxylic esters with silanes [9, 10]. The yields of sulphoxides... 

Carbon disulphide should not be used as the solvent for alkylation of fS-diketones, as the carbanion reacts preferentially with the solvent to generate the dithiocarboxyl-ate derivative, which undergoes mono- and dialkylation (Scheme 6.9) [95]. Ketene thioacetals have also been isolated from acetophenones (60-80%) and cyclopenta-diene (80%) using an ultrasound technique in carbon disulphide [96] and, in a similar manner, pyrazol-5-ones form pyrazole-4-dithiocarboxylic esters [97]. 

BC13 convert 0=0 groups of ketones, lactones, and lactams to G=S groups119 and H2S-Me3SiCl-i-Pr2NLi converts carboxylic esters to thiono esters.120 Carboxylic acids RCOOH can be converted directly to dithiocarboxylic esters RCSSR, 120a in moderate yield, with P4S, and a primary alcohol R OH.121 Thioketones can also be prepared by treatment of ketones with P4SI0,122 and from oximes or various types of hydrazone (overall conversion C=N------> C=S).123... 

Several methods for the synthesis of dithiocarboxylic acids and esters have been pub-lishedJ84-86 They have been summarized by Ramadas et alJ8T ... 

The interchange reaction between a thioxoester and a thiol does not, in general, represent a meaningful synthetic procedure since dithioesters are more readily available than thioxoesters in most cases. However, 0,S-diethyl tiithiomalonate (61b) and diethyl tetrathiomalonate (61c) were prepared from 0,0-di-ethyl dithiomalonate (61a). On the other hand, the transformation of one dithiocarboxylic ester into another can be a useful and practicable reaction. For instance, ethyl arenecarbodithioates are intercon-verted to 2-dialkylaminoethyl arenecarbodithioates, according to equation (62). 

Imidothioates in the neutral or ionic form are the most generally applied educts for the preparation of dithiocarboxylic esters. They are themselves prepared from nitriles, thioamides or isothiocyanates, and react with hydrogen sulfide under appropriate conditions to yield the dithioesters (Scheme 7) 6,14,26,27,29,141 Interesting examples (62)-<73) were described in the recent literature. 

Both cis and rrafw-3-phenoxycinnamic acids cyclize with phosphorus pentoxide to pyran>4-ones but the corresponding phenylthiocinnamic acid isomers behave differently the traits isomer gives a thiopyranone whereas the cis compound produces an indenone. Diels-Alder reactions with heterodienes have been reviewed [24SS, 3067a, 3880]. Indole-3-dithiocarboxylate esters act as dienes in the Diels-Alder reaction with DMAD (cf. Chapter 65, Section II.7). 

Magnesium salts 12 are the most important among the dithiocarboxylate salts of alkaline earth metals. Magnesium salts 12 are prepared by insertion of CS2 using Grignard reagents (Scheme 4) [41]. These salts 12 are treated with acid, alkyl halides and alkyl triflates to prepare dithiocarboxylic acids and esters, respectively [42-45]. A dinuclear aluminum-magnesium compound 13 is also synthesized by insertion of CS2 into the Mg-C bond (Fig. 4) [46]. 

The following example involves the interaction between dithiocarboxylate sulfur and cyclopropane ring. Thus, treatment of the ester enolate, generated from (29), with carbon disulfide and... 

Monotbio-j -diketones. Acetophenone added slowly with stirring to a suspension of NaNHg in ether, after 15 min. an ethereal soln. of 0-methyl thiobenzoate added, stirred 3 hrs., and allowed to stand overnight monothiodibenzoyl-methane. Y 68%. E. Uhlemann and H. Muller, Ang. Gh. 77, 172 (1965) with Li, also from dithiocarboxylic acid esters, and f. method, s. E. Uhlemann and H. Muller, J. pr. 30, 163 (1965). 

Prepn. from N,N-disubst. carboxylic acid amides—Thiocarboxylic acid esters Dithiocarboxylic, thiolic, and thionocarboxylic acid esters—Ring closures to heterocyclics s. 19, 628 a-chlorimmonium chlorides cf. M. Grdini6 and V. Hahn, J. Org. Chem. 30, 2381 (1965)... 

LR, for the thionation of carbonyl groups. DR is, however, considerably more reactive and in many cases more selective than LR. Furthermore, it exhibits the unique ability to transform carboxylic acids into dithiocarboxylic esters in one step. Similar dithiadiphosphetane disulfides with arylthio substituents have been designed in order to achieve an even improved effectiveness in thionation reactions and also to produce a more conveniently handled reagent compared with the obnoxious DR. The so-called Japanese reagent (JR), 2,4-bis(phenylthio)-l,3,2,4-dithiadiphosphetane 2,4-disulfide, has recently found considerable synthetic application. 

Thionation of Carbonyl Compounds. Diaryl thioketones and 2,4-bis(diphenylmethylene)cyclobutane-l,3-dithione were obtained on reaction of the corresponding ketones with DR. On the other hand, JR was utilized to thionate selectively the carbonyl group of benzil monophenylimine. If carboxylic esters or lactones are reacted with DR, dithiocarboxylic esters or dithiolac-tones are formed, i.e. the carbonyl group is thionated and the alkoxy group is substituted by an aUcylthio group. Bis(5-methyl-2-thienyl) disulfide is produced in this way from a butenolide (eqS). ... 

Dithiocarboxylic acid esters from dithiocarboxylic acids and ethylene derivs. 

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