Thioformates

Thio-ameisensiiure, /. thioformic acid, -anti-monsaure, /. thioantimonic acid, -arsenig-saure, /. thioarsenious acid, -arsenaaure, /. thioarsenic acid, -ather, m. thio ether, -car-baminsaure,/. thiocarbamic acid. 

Beim Einsatz von vier Hydrid-Aquivalenten erhalt man bei 25° 49% d.Th. Thioform-anilid, bei 90° 6% d.Th. Anilin und 74% d.Th. N-Methyl-anilin. 

The mechanism of the condensation in Part D probably involves thioformylation of the metallated isocyanoacetate followed by intramolecular 1,1-addition of the tautomeric enethiol to the isonitrile. This thi2izole synthesis is analogous to the formation of oxazoles from acylation of metallated isonitriles with acid chlorides or anhydrides. " Interestingly, ethyl formate does not react with isocyanoacetate under the conditions of this procedure. Ethyl and methyl isocyanoacetate have been prepared in a similar manner by dehydration of the corresponding N-formylglycine esters with phosgene and trichloromethyl chloroformate, respectively. The phosphoryl chloride method described here was provided to the submitters by Professor U. Schollkopf and is based on the procedure of Bohme and Fuchs. The preparation of O-ethyl thioformate in Part C was developed from a report by Ohno, Koi/.uma, and Tsuchihaski. " ... 

O-Ethyl thioformate Formic acid, thio-, O-ethyl ester (8) Methanethioic acid, O-ethyl ester (9) (29392-46-9)... 

Moreover, potential reactions can be written for conversion of dithioformic acid to thioformic acid (Equation 3), and hence COS. 

An alternate potential fate for the CH3SCH20 radical is the well-known abstraction reaction of alkoxy radicals with 02, forming methyl thioformate (Crutzen, 1983 Butkovskaya and Le Bras, 1994) ... 

Infrared absorption bands attributable to methyl thioformate have been observed in the oxidation of DMS by OH in the absence of NOx but not when NOx was present (Barnes et al., 1996 Patroescu et al., 1999). Reaction (51) appears to be quite slow (k < 1 X 10 15 cm2 molecule-1 s-1), so that the dominant fate of CH3SCH20 is decomposition to HCHO + CH3S Turnipseed et al. (1996) measured the production of CH3S in the reaction of OH with DMS and also suggest, based on its relatively high yield, that the thermal decomposition (50) predominates over reaction (51) with 02 to form methyl thioformate. The methyl thioformate observed in laboratory systems in the absence of NO is thus likely due to cross reactions of CH3SCH200 with itself or other R02 (Barnes et al., 1994a), and the abstraction channel in the OH + DMS... 

If f-hydroxy-2-oxa-4,6-dithioheptane-7-thiol is isolated and heated under vacuum, formaldehyde and hydrogen sulfide are eliminated and poly(thioform-aldehyde) is formed. This can be done by heating the dithioheptane at 210° C for 6 h in vacuo. 

Dihydrothiazines are useful in the formation of cephems and the derivative (205), for example, was prepared from the bromoester (204) and ethyl thioformate specifically for this purpose (B-80MI22701). 

The fluoro-thioformate complex [Pt(S2CF)(PPh3)2] [HF2] is synthesized by the reaction of CS2 with [PtF(PPh3)] [HF2]. The structure of the product of this interesting CS2 insertion reaction has been determined (Table XXIII). A distorted square planar coordination around the Pt atom is found, as well as a bidentate S2CF ligand (225). 

The dihydrothiazol-2-ylidene (4) was generated by photolysis of matrix-isolated thiazol-2-carboxylic acid.12 Calculations suggested that the barrier to isomerization to thiazole is about 42.3 kcal mol 1 and that the carbene resembles the related imidazol-2-ylidene in structure. An ab initio study of hydroxyoxiranone predicted that the decarboxylation of the zwitterion (5) to form hydroxycarbene (6) would be favourable in vacuo but not in water.13 A theoretical study showed that dihalosulfenes (X2C=S02) are best viewed as dihalocarbenc-SO complexes with a carbon-sulfur bond order of approximately zero.14 hi a study directed at the elusive thionformic acid (7), tandem mass spectrometric methods were applied to isomeric ethyl thioformates.15 The results suggest that the radical cations generated have the carbene structure [(HS)C(OH)]+ ... 

TABLE 5. Relative stability (kcalmoG1) of the s-cis (4a) conformer of thioformic acid with respect to the s-trans (4b)... 

Another interesting problem related to the thiol/thione tautomerism in thioformic acid is the relative stability of the s-cis (4a) and s-lrans (4b) conformers of the thiol form. As we have mentioned in the preceding section, the former is 0.7 kcal mol 1 more stable than the latter. A much larger energy difference is predicted to exist, at the ab initio level, between the s-cis (23a) and s-trans (23b) forms of formic acid (oc6.2 kcal mol 1) or between the same conformers of the thione form of thioformic acid (4c, 4d) (oc6.5 kJmol l)llx. 

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