Sulfines, heterocycles from

The tosyl group could alternatively be eliminated during the reaction when a base, such as l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), was present, as is the case for the photolysis of 1,2-diaryl-l-tosylstilbenes that led to phenanthrenes or their heterocyclic analogues in one step (Scheme 14.15, path h). These results were consistent with a mechanism involving a base-induced ehmination of p-toluene-sulfinic acid from 9-tosyl-4a,4b-dihydrophenanthrene as intermediate, formed by photochemical cyclization of the starting ethene [88]. 

A wide variety of sulfines has been produced by the oxidation reaction with mCPBA starting from dithioesters [104, 105], trithioperesters [106], heterocyclic C=S compounds [107], thionoesters [108] (see also [109]), dit-hiocarbonates [110] and trithiocarbonates [111]). 

This traceless linker allows fhe synthesis of a number of different heterocycles starting from fhe solid-phase-bound sulfone intermediate 139, which can be built up in a few steps from fhe sulfinate 138. The potential of fhis traceless linker is outlined in Scheme 66 [161, 162]. 

The oxidative desulfurisation of 1,2,4-triazole thiones is a type of reaction common to other electron-deficient nitrogen heterocycles nitric acid is the oxidant in the example below. The process involves loss of sulfur dioxide from an intermediate sulfinic acid. ... 

The use of potassium metabisulfite serves two roles (1) it serves as a source of SO2 and (2) it buffers the reaction solution so that decomposition of the intermediate sulfinate does not oeeur via disproportionation. Importantly, the intermediate sulfinate can also be reaeted with allg l halide electrophiles to produce sulfones in addition to aryl sulfonamides. The current methodology addresses the key limitation of the Buehwald protocol as it tolerates N-heterocycles. To demonstrate the rapid synthesis of analogues, sildenafil and ten sulfonamide analogues were prepared in a parallel fashion from a late stage intermediate. Potassium metabisulfite has also been utilised as a convenient SO2 source in the gold-eatalysed sulfonami-dation of aryl boronic acids." ... 

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