5-Methyl 1- dithiocarbonate, free

J. Marco-Contelles, P. Ruiz-Femandez, and B. Sanchez, New annulated furanoses A new free-radical isomerization of an S-methyl hex-5-enylxanthate to an 5-(cyclopentylmethyl) S-methyl dithiocarbonate, J. Org. Chem. 58 2894 (1993). 

O-Allyl-5-alkyl dithiocarbonates react with Pd° catalysts to provide a ir-allyl complex with a thiocar-bonate serving as counterion. Under the reaction conditions the carbonate expels free methyl meicaptide, generating COS. Attack of the mercaptide was shown to occur exclusively via ligand addition (equation 195).221... 

Carbon disulfide is the dithio derivative of C02. It is only a weak electrophile. Actually, it is so unreactive that in many reactions it can be used as a solvent. Consequently, only good nucleophiles can add to the C—S double bond of carbon disulfide. For example, alkali metal alkoxides add to carbon disulfide forming alkali metal xan-thates A (Figure 7.4). If one were to protonate this compound this would provide compound B, which is a derivative of free dithiocarbonic acid. It is unstable in the condensed phase in pure form, just as free carbonic acid and the unsubstituted carbamic acid (Formula B in Figure 7.3) are unstable. Compound B would therefore decompose spontaneously into ROH and CS2. Stable derivatives of alkali metal xanthates A are their esters C. They are referred to as xanthic add esters or xanthates. They are obtained by an alkylation (almost always by a methylation) of the alkali metal xanthates A. You have already learned about synthesis applications of xanthic acid esters in Figures 1.32, 4.13, and 4.14. 

A free-radical approach has also been successfully applied to the synthesis of primary allylic tributylstannanes (Eq. 8) [10]. The sequence involves a thermal [3,3] rearrangement of an allylic methyl xanthate then addition of a BusSn radical to the double bond of the derived dithiocarbonate intermediate and subsequent loss of COS in a chain-propagating step. 

Free radical coupling of 5-methyl l-(/3-D-ribofuranosyl)dithiocarbonate (97), as ribofuranosyl radical precursor, and A-ethylmaleimide (98) gave a mixture of the a and /3-dihydro-A-ethyl showdomycins 99 (88TL351) (Scheme 18). 

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