Dithiocarbonate £>- 2-alken

S-methyl dithiocarbonate (76S413). Stereoselective isomerization of 1,2-disubstituted alkenes may be achieved by a sequence such as the following fr<2n5-alkene bromo-hydrin -> /3-hydroxythiocyanate -> cw-thiirane -> cw-alkene (75TL2709). 

In Figure 4.14, we learned about the Chugaev elimination in connection with the synthesis of alkenes. The second (primary) product of this reaction is the dithiocarbonic acid 5-methyl ester (A). It equilibrates with the zwitterion B, which decomposes into carbon oxysulfide (a heterocumulene) and methanethiol (a heteroatom nucleophile). 

Figure 8. Synthetic routes to alkene dithiocarbonates (dithioles) and their conversion to dithiolene complexes.

A versatile route to RS-substituted dithiolenes entails S-alkylation of the trithiocarbonate dmit2 (see Section II.C.l), which provides an efficient means to introduction of diverse functionality to the dithiolene backbone. Subsequent to S-alkylation, the resulting S=CS2C2(SR)2 is converted to the dithiocarbonate 0=CS2C2(SR)2 with Hg(OAc)2 in acetic acid (63, 83, 84). Such dithiocarbo-nates are more easily hydrolyzed than the trithiocarbonates (72, 85). This approach has been used for the synthesis of Ni[S2C2(S(CH2) Me)2]2 (n = 2-11) (86) and related complexes with pendant alkene substituents (Eq. 8) (87). 

The reaction of 0-methyl A-prop-2-ynyl dithiocarbonates 523 with alkenes 524 led to 1,3-dithiol-2-one derivatives... 

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