S thiocarbamates

Aryl O-Carbamate and S-Thiocarbamate-Grignard Cross-Coupling Reactions... 

A logical progression of O-carbamate DoM chemistry, to metalate S-thiocarbamates 103, E = H, proved unsuccessful, but turning attention to the corresponding O-thiocarbamates... 

Scheme 33. DoM of aryl O-thiocarbamate. Link to the Newman-Kwart rearrangement and consequent S-thiocarbamate cross-coupling.

S-Thiocarbamic acid esters from thiocyanates SCN —>- SCONH ... 

Rearrangement of O-Thiocarbamates to S-Thiocarbamates (Newman-Kwart Rearrangement) Another mechanistically related reaction to the Chapman rearrangement is that named after Newman [32] and Kwart [33]. This particular variant involves the 1,3-migration of an aryl group from oxygen to sulfur in a thiocarbamate (Scheme 18.11), and the reaction has recently been reviewed [34]. 

SCHEME 18.11 The Newman-Kwart rearrangement of an O-thiocarbamate to an S-thiocarbamate. 

In the Newman-Kwart Rearrangement (NKR), intramolecular aryl migration of O-thioearbamates at high temperatures leads to S-thiocarbamates. The NKR allows access to thiophenols from phenols, as O-thiocarbamates are readily prepared and hydrolysis of S-thiocarbamates can readily be achieved (Moseley and Lenden, 2007). The yield ranges between 72-91%. 

Thus the condensation of dichloroether or chloroacetone fails to give the parent compound, 2-hydroxythiazole (158a), Rj = R2 = R3 = H (221). However, 2-hydroxythiazole can be obtained in 12% yield from chloro-acetaldehyde (386). The condensation of ammonium thiocarbamate with cf-chloroketones gives the corresponding 2-hydroxy derivatives in 25 to 70% yields (76, 221, 304, 412) (Table 11-24). These compounds condensed with ClP(S)(OEt)2 give the corresponding 2-thiazolyl-thiophosphates (791). 

Human perception creates difficulty ia the characterization of flavor people often, if not always, perceive flavors differently due to both psychological and physiological factors. For example, certain aryl thiocarbamates, eg, phenylthiocarbamide, taste exceedingly bitter to some people and are almost tasteless to others (5). This difference is genetically determined, and the frequency of its occurrence differs from one population to another 40% of U.S. Caucasians are nontasters, whereas only 3% of the Korean population caimot perceive the strong bitter taste of the aryl thiocarbamates (6). Similar differences were found ia the sense of smell for compounds such as menthol, carvone, and ethyl butyrate (7). 

FREUDENBERG - SCHdNBERG Xanthate Rearrangement Rearrangement of S-methyl xanthates to S-methyIdithiocarbonatas (conversion of alcohols lo thiols via xanthates, also phenols to thiophenols via thiocarbamates). 

S-Benzyl Thiocarbamate, 548 Butynyl, 548 p-Cyanobenzyl, 548 Cyclobutyl, 548 Cyclohexyl, 548 Cyclopentyl, 548 Cyclop ropy I methyl, 548 p-Decyloxybenzyl, 548 Diisopropylmethyl, 548 2,2-Dimethoxycarbonylvinyl, 548... 

In 1999, it was reported that the palladium catalyzed azathiolatiori, that is, the addition of the S-N bond of sulfenamide 115 to carbon monoxide can be catalyzed by palladium(O) complexes in pyridine to provide the thiocarbamate 116 in good yields (Eq. 7.69) [67]. Contrary to the other S-X bond activations described so far, where X has the same electronegativity as S (i.e. X = S) or lower (X = H, B, Si, Ge, and P), the S-N bond has a strong S -N bond character and shows unique reactivity. 

In analogy to the preceding Section 7.1.5 the insertion of a C=0 or C=S group between an amino and a hydroxy function of 1,3-aminoalcohols using CDI or ImCSIm yields six-membered heterocycles with a carbamate or thiocarbamate structure. 

Thiocarbamate (tc, RHNCSO-) is a monodentate ambidentate ligand, and both oxygen- and sulfur-bonded forms are known for the simple pentaamminecobalt(III) complexes. These undergo redox reactions with chromium(II) ion in water via attack at the remote O or S atom of the S- and O-bound isomers respectively, with a structural trans effect suggested to direct the facile electron transfer in the former.1045 A cobalt-promoted synthesis utilizing the residual nucleophilicity of the coordinated hydroxide in [Co(NH3)5(OH)]2+ in reaction with MeNCS in (MeO)3PO solvent leads to the O-bonded monothiocarbamate, which isomerizes by an intramolecular mechanism to the S-bound isomer in water.1046... 

Trichloroacetyl chloride, 6 269 S-2,3,3-Trichloroallyl diisopropyl-(thiocarbamate), 2 549t... 

The l3C chemical shifts of methyl derivatives with sulfur substituents [e.g., SH, -S, -SCH3, -SSCH3, -SSSCHj, -S(0)CH3, -S02CH3, -S(CH3)2+, -SC(0)CH3, -SC(S)CH3, and -SC(S)SCH3] (130,131) and of vicinal and gem-inal bis-sulfides (290) have been reported. Freeman and co-workers have published similar studies on thiols, sulfides, disulfides, and sulfinic and sulfonic acid derivatives (131,132,433) and Tseng and Bowler (434), on thiocarbamates, their S-oxides and S,5-dioxides [R-X-C(0)-NR 2 with X = S, SO, S02]. 

Haloarene chromium tricarbonyl complexes are activated to nucleophilic attack by thiolate anions [58, 59]. High yields of the thioethers are obtained under liquiddiquid two-phase conditions, but optimum yields are achieved under soliddiquid conditions. In many cases the thioether is produced directly but, where the reaction mixture contains thioether and its chromium complex, the thioether can be isolated by degradation of the complex with iodine or an excess of the thiol. Both 1,2- and 1,4-dichlorobenzenes yield only monothioethers, even when an excess of thiolate anion is used. In contrast, 1,3-dichlorobenzenes produce a mixture of the mono- and dithioethers [59]. Aryl allyl thioethers have been produced under catalysed Heck reaction conditions from S-allyl thiocarbamates and iodobenzene [60]. 

S -Alkyl thiocarbamates (Table 4.24) have been synthesized [I] by a procedure (Scheme 4.19) which is closely analogous to that employed for the preparation of S-alkyl thiocarbonates (see Section 4.1), S-Glycosyl dithiocarbamates [2], which are useful precursors for thiosugars, have been prepared by simple nucleophilic displacement of the tosyloxy group by the N,N-diethyldithiocarbamate anion (cf preparation of S-glycosyl dithiocarbonates, 4.1.13). 

Selected examples of the synthesis of S-alkyl thiocarbamates Amine Haloalkane % yield... 

Breiter. W.A.. Baker. I.M.. and Koskinen. W.C. Direct measurement of Henry s constant for 5-ethyl TV.TV-di-n-propyl-thiocarbamate. J. Agric. Food Chem., 46(4) 1624-1629.1998. 

Kwok, E.S.C., Atkinson, R., and Arey, R. Gas-phase atmospheric chemistry of selected thiocarbamates. Environ. Scl Technol, 26(9) 1798-1807, 1992. 

Square-planar co-ordination about Pd. One thiocarbamate ligand coordinates through both S and N, while other is unidentate through S. 

Approximate square plane about Pd. Both thiocarbamates are bidentate, bonding through S and N. 

As the thiocarbamate S-oxides behave similarly to those of the alkylmercapto-s -triazines in other respects, it would be of interest to investigate their reactivity to haemoglobin. 

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