Carbon disulfide elimination

Carbon disulfide elimination (Eq. 55) appears to be a general reaction of the thioxanthate complexes (153). 

The kinetics of the carbon disulfide elimination reaction were studied using PMR and visible spectroscopy (16). This spontaneous reaction was found to be first order in the M(RSXant)2 complexes (M = Ni, R = Et, r-Bu, Bz M = Pd, R =/ -Bu), both in the disappearance of the starting material and in the formation of the mercaptide-bridged species in CHC13 and THF. The pseudo-first-order kinetics observed in CS2 are attributed to an equilibrium between the M(RSXant)2 complexes and this solvent. Rate constants for the reaction are of the order of 10 3 to 10"1 min"1 depending on solvent, temperature, alkyl... 

Characteristic of the heavy metal complexes is their carbon disulfide elimination, yielding mixed thiol-thioxanthato complexes with trimeric structures and thiol bridges.139 The facile nucleophilic substitution of RS by R2N is interesting.113114... 

Salts of dithiocarbamic acid can be prepared by the addition of primary or secondary amines to carbon disulfide. This reaction is similar to 16-9. Hydrogen sulfide can be eliminated from the product, directly or indirectly, to give isothiocyanates (RNCS). Isothiocyanates can be obtained directly by the reaction of primary amines and CS2 in pyridine in the presence of DCC. ° In the presence of diphenyl phosphite and pyridine, primary amines add to CO2 and to CS2 to give, respectively, symmetrically substituted ureas and thioureas ... 

A novel synthesis of alkylsulfanylisothiazoles 230 starts with sodium a-cyanoketene dithiolates 227, obtained by the reaction of cyanoacetamides 226 with carbon disulfide in the presence of sodium ethoxide <06SC825>. Treatment of 227 with sulphur and piperidine acetate generates sodium isothiazole-3,5-dithiolates 229. The formation of 229 is assumed to arise from the addition of anionic sulphur to the nitrile group in 227 to give the intermediate 228, which cyclizes upon elimination of anionic sulphur to yield 229. Salts 229 are readily alkylated to furnish 3,5-bis(alkylthio)isothiazole derivatives 230. 

Transformation of the thiadiazolopyrimidine compound 138 to the fused dithiazole 140 also follows a fairly complicated pathway <2004JHC99>. When the derivative 138 is treated with carbon disulfide, a cyclization reminiscent of 1,3-dipolar cyclization takes place with the reagent acting as a dipolarophile to give a />OT-fused tricyclic intermediate containing a hypervalent sulfur atom 139. This intermediate can undergo isothiocyanate elimination to furnish 140. It is interesting to note that the sulfur atom of the thione moiety in the product is derived from carbon disulfide. 

Reiter and co-workers found in the course of their extended research on fused [l,2,4]triazines <1994JHC997> that the N-protected methylthiotriazine derivative 110 when reacted with carbon disulfide under strongly basic conditions yields a mixture of two products 111 and 112. When this mixture was treated with dibromomethane, product 113 was easily removed from the reaction mixture, and workup of the mother liquor allowed the isolation of the [l,2,4]triazolo[l,5-c][l,3,5]thiadiazine derivative 114 in 49% yield (Scheme 21). The same authors carried out ring closure of the ring-closed semithiocarbazide 115 to the triazolothiadiazine derivative 118 as shown in Scheme 21 <1997JHC1575>. The starting compound was treated with triethyl orthoformiate. The authors assume that first intermediate 116 is formed which cyclizes to a second intermediate 117 and, finally, ethanol elimination yields the isolated product 118. 

Investigation of transformations of the zwitterion 207 led to the elaboration of a new synthetic route to imidazo[ 1,2-t]-thiadiazines <2003JOC4791>. Treatment of this compound 207 with carbon disulfide in the presence of sodium hydroxide resulted in elimination of carbon oxide sulfide and in formation of the cyclized product 208. 

Reaction of carbon with sulfur dioxide was observed by Fischer and Prauschke (131). In my laboratory it was recently found that sulfur is bound by heat-treated carbon blacks and by graphitized carbon black on treatment with hydrogen sulfide, carbon disulfide, or sulfur dioxide at low temperatures, even at room temperature. The sulfur content cannot be eliminated by outgassing at 100° or by prolonged extraction with various solvents. 

Amidoximes (46) were first used as a source of 1,2,4-thiadiazoles in 1889 their condensation with carbon disulfide or with an excess of aryl isothiocyanate yields 3-aryl-5-mercapto- (47)6 -73 or 3-aryl-5-aryl-amino- 1,2,4-thiadiazoles (50),71,74,75 respectively. The latter reaction has been reexamined and discussed by Gheorgiu and Barbos76 who suggest that an initial addition of two moles of phenyl isothiocyanate to one of benzamidoxime is followed by cyclization of the intermediate (49), with elimination of phenylthiocarbamic acid (51). Decomposition of the latter gives rise to the by-products observed (cf. following scheme). 

To complete this series of heterocumulene syntheses from carbonic acid derivatives, we here present the acid- and base-catalyzed alcohol elimination from carbamic acid esters (C, Figure 8.10) and the condensation of aniline and carbon disulfide to phenylisothiocyanate (F,... 

Fig. 8.11. Tandem reaction consisting of three single reactions mutually transforming heterocumulenes and heteroatom nucleophiles in a one-pot synthesis of an isothiocyanate (1) uncatalyzed addition reaction of heteroatom nucleophile (aniline) + heterocumulene (carbon disulfide) —> carbonic acid derivative (A) (2) heterolysis-initiated /3-elimination of the carbonic acid derivative (D) -> heterocumulene (F = phenylisothiocyanate) + heteroatom nucleophile (thiocar-bonic acid O-ethylester) (3) decomposition of a carbonic acid derivative (D) to a heterocumulene (carbon oxysulfide) and a heteroatom nucleophile (ethanol) via the zwitterion H.

Fig (19) Octalin ketal (163) is converted to kete dithioacetal (164) by the cleavage of ketal function and condensation with carbon disulfide and methyl iodide. Subjection of (164) to the action of dimethylsulfonium niethylide and acid hydrolysis leads to the formation of unsaturated lactone (165).lts furan silyl ether derivative is caused to undergo Diets-Atder reaction with methyl acrylate to obtain salicyctic ester (166) which is converted by standard organic reactions toabietane ether (167). It is converted to aiiylic alcohol (168) by epoxidation and elimination. Alcohol (169) obtained from (168) yields orthoamide which undergoes transformation to amide (170). Its conversion to the previously reported intermediate has been achieved by epoxidation, elimination and hydrolysis. 

Animals. Mostly eliminated within 1-2 days leaving 1-2% of the dose in the tissue and carcass after 7 days Plants. The major metabolite is dimethylamine salt of dimethyldithiocarbamic acid tetramethylthiourea, carbon disulfide and sulfur can also be formed. Dimethyldithiocarbamic acid can be present as the free acid or as the metabolic conversion products DDC-/3-glucoside, DDC-a-aminobutyric acid and DDC-a-alanine Soil. A. aerobic DT50 42 hr. Unlikely to leach... 

Substituted quinazoline-4(3/7)-thiones 1 react with tosyl isothiocyanate with elimination of carbon disulfide to give the corresponding 4-tosylimino-3,4-dihydroquinazoline derivatives 2. ... 

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