Trithiocarbonates, cycloaddition

Cycloadditions of benzonitril-4-nitrobenzylide to a variety of carbon to heteroatom multiple bonds including methyl dithiobenzoate and dimethyl trithiocarbonate (Scheme 148), X = MeS or Ph, have been examined in detail by Huisgen et al. (757). 

The dipolar 1,3-cycloaddition reaction of thiocarbonyl ylides to thiones can be a source of 1,3-dithiolanes. Its regioselectivity depends on the nature of substituents in the substrates. Thus, the. J-methylide 589, generated in situ by thermal decomposition of the corresponding l,5-dihydro-l,3,4-thiadiazoles, was reacted with the trithiocarbonate 588 to give a labile 4,4,5,5-tettasubstituted-l,3-dithiolane 590, which easily isomerized to an open-chain compound 591 in the presence of acids in solution (Scheme 84) <2000EJ01695>. 

The cyclic ylide 592 reacted with the trithiocarbonate 588 to give the 2,2,4,4-tetrasubstituted-l,3-dithiolane 593 in a moderate (42%) yield. The regioselectivity of this cycloaddition was opposite to that observed for the ylide 589 (Scheme 84) <2003CEJ2256>. 

Also, trithiocarbonate 5-oxides 34 undergo the [4+2] cycloaddition reaction with 2,3-dimethyl-1,3-butadiene to give the corresponding [4+2] cycloadducts 35. ... 

Trithiocarbonate 55 -dioxides ArS02CSaAr undergo [4 + 2] cycloaddition with 1,3-dienes to afford the unstable A -dihydrothiopyrans (1), which readily lose ArSOaH to give the corresponding 2J -thiopyrans. Addition of ArSOaH to these 2/f-thiopyrans gives the 4-arylsulphinyl-2-arylthio-A -dihydrothiopyrans isomeric with (1). Evidence for the existence of the unstable 4-thioxotetrahydro-furan-3-ones was obtained by trapping them with 2,3-dimethylbuta-l,3-diene, which yielded the spiro-compounds (2) these underwent unusual mass spectral... 

The cycloaddition of (27) to dimethyl trithiocarbonate occurs readily in the cold in a direction opposite to that of (di)thiobenzoates, yielding (31) the... 

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