Dithiocarboxylates, methyl

A -Methylation of the NH of heterocycles using 1 is also known as exemplified by the methylation of indole/ The interesting mechanism is delineated below. O-methylation of weak acids such as phenols, carboxylic acids and oximes as well as 5-methylation such as A -phenylisorhodanine, certain thioketones, and dithiocarboxylic acids have also been reported." ... 

This method is not general and only a limited number of 5-alkyl-l,2,3,4-thiatriazoles were prepared by this reaction. Ikeda and co-workers have described a convenient method for the synthesis of both 5-alkyl- and 5-aryl-l,2,3,4-thiatriazoles 9 by reaction of l-methyl-2-thioacylpyridinium salts 143 with sodium azide (Scheme 33). Compound 143 can be prepared from pyridium salt 142 by reaction with dithiocarboxylic acid derivatives. The synthesis can conveniently be carried out as a one-pot reaction from 2-chloro-l-pyridinium salt 142 and carbodithioate leading to final compounds 9 in high yields. The 5-alkyl-l,2,3,4-thiatriazoles 9 were isolated as oils <1990S415, 1990ZC67>. 

Cyclization of a,abis(dimethylthiomethylene) ketones by phosphorus pentasulfide leads to 2,5-bis(methylthio)-l,6,6aA4-trithiapentalenes (equation 7) (71AHC(13)161, p. 185). Condensation of carbon disulfide with pyrrolidin-2-one in basic medium, followed by methylation of the reaction product, leads to methyl 3-(dimethylthiomethylene)-2-oxopyrrolidine-l-dithiocarboxylate. This compound, when treated with phosphorus pentasulfide and perchloric acid, yields the 2,5-bis(methylthio)-l,6,6aA4-trithia-2aA5-azacyclopenta[a/]pen-talen-2a-ylium cation. With e- caprolactam similar results are obtained (76BSF1200). 

Compound 96 reacts with SR-, with ring cleavage and loss of sulfur, to form the methyl ester of the 1-alkylmercaptocyclopent-l-ene 2-dithiocarboxylic acid (97). Compound 96 reacts in a similar manner with primary amines (see below). 

Piperazine-2,5-dione treated with sodium hydride in A,A-dimethylacetamide and carbon disulfide followed by esterification with methyl iodide gave l-methylthio(thio-carbonyl)piperazine-2,5-dione (methyl 2,5-dioxopiperazine-l-dithiocarboxylate) and l,4-bis[methylthio(thiocarbonyl)]piperazine-2,5-dione (107), but when the reaction was carried out in dimethyl sulfoxide containing tetrahydrofuran it afforded (107) plus 3-[bis(methylthio)methylene]-l-methylthio(thiocarbonyl)piperazine-2,5-dione (108) (1630). 

Abbreviations Ac acetyl AIBN azobisisobutyronitrile All allyl Bn benzyl Bz benzoyl ClAc chloroacetyl DAST diethylaminosulfur trifluoride DBU l,8-diazabicyclo[5.4.0]-undec-7-ene DDQ 2,3-dichloro-5,6-dicyano-/)-benzoquinone DMDO dimethyldioxirane DMTST dimethyl(methylthio)sulfonium trifluoromethanesulfonate Fmoc 9-fluorenyl-methoxycarbonyl HDTC hydrazine dithiocarboxylate IDCP iodonium di-collidine perchlorate Lev levulinoyl MBz 4-methylbenzoyl Me methyl MEK methyl ethyl ketone MP 4-methoxyphenyl NBS iV-bromosuccinimide NIS A-iodosuccinimide Pent n-pentenyl Pfp pentafluorophenyl Ph phenyl Phth phthaloyl Piv pivaloyl PMB 4-methoxybenzyl TBAF tetrabutylammonium fluoride TBDMS tcrt-butyldimethylsilyl TBDPS tert-butyldiphenylsilyl TCA trichloroacetyl TES triethylsilyl Tf trifluoromethanesulfonyl TMS trimethylsilyl Tol 4-methylphenyl Tr trityl Troc 2,2,2-trichloroethoxycarbonyl Ts tosyl. 

The method of atomic absorption spectrometry is very convenient for concentrations 0.002 mg 1 . Cadmium is concentrated by evaporation or extraction in the form of a complex salt of 1-pyrrolidine dithiocarboxylic acid into methyl isobutyl ketone. The absorbance of the cadmium line is measured at 228.8 nm [13]. 

Analogous reactions of a-halogenoesters have been less explored, but an example is shown in Scheme 48. A reaction of 2,6-dimethylpyridine with ethyl chloroacetate gave the pyridinium salt (210), which on reaction with carbon disulfide in the presence of sodium hydroxide and subsequent meth-ylation with dimethyl sulfate gave methyl 5-methyl-2-hydroxyindolizine-3-dithiocarboxylate (211) (81YZ980). 

The dithiocarboxylate salts of alkali metals readily react with alkyl halides. The lithium, sodium, and potassium salts 1-3 readily react with methyl iodide to give the corresponding methyl ester 11 at room temperature in good yields, while similar reactions of rubidium and cesium salts 4 and 5 result in low yields (Scheme 3) [38]. 

Although CS2 insertion into the metal-carbon bond is rarely used to synthesize dithiocarboxylate salts of Group 14 elements, divalent tin salts of the dithiocar-boxylates 70 and 71 are synthesized by this method (Fig. 18). They are obtained by the stepwise insertion of CS2 into two Sn-C bonds of a diarylstannylene, Sn-[2,4,6- t-Bu) C L2 2 [128]. Reaction of another stannylene Sn 2,4,6-[(Me3Si)2-CH]3C6H2 [2,4,6-(z-Pr)3C6H2] with CS2 produces the stannylene-CS2 ylide 72, which is trapped by methyl acrylate to afford cyclic stannyl dithiocarboxylate 73 (Scheme 17) [129]. 

There are some reports of syntheses and reactivities of inner salts of dithio-carboxylate, such as the bis(iV,Ar-substituted amino)carbenium dithiocarbox-ylates 87 [138-143]. The carbenium and dithiocarboxylate moieties are nearly perpendicular to each other in a quasi-plane [19,20,144]. Its sulfur atom reacts not only with methyl iodide to give carbenium iodide 88 [145], but also with organometallic reagents RM (M=Li,MgX) to give thiolates 89 [146],revealing a unique ability to serve both as a nucleophile and as an electrophile (Scheme 22). Furthermore, 87 is S-iminated by [iV-(p-tolylsulfonyl)imino]phenyliodinane to provide a novel inner salt 90 that formally possesses a thione-S-imide structure 90 as one of its canonical structures [143]. 

S-methyl-dithiocarboxylate and substituted benzaldehydes or heterocyclic aldehydes react with NiClj and Ni(OAc)2 to produce the neutral square-planar complexes [ RCH=NN=C(SMe)S 2Ni](R = Ph,p-Me0C H, p-T[Pg.291]

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). 

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). ... 

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