Pyrrole sulfinylation

RC=CKWG) yields 2,4-di-EWG-substituted pyrroles in the presence of copper catalyst but 2,3-di-EWG-substituted pyrroles in the presence of a phosphine catalyst.74 The 3 + 2-cycloaddition of diazoalkanes to (6 )-3-p-tolylsulfinylfuran-2(5//)-one produces diastereoisomeric pyrazolines in almost quantitative yield and with des >98%. (g) The sulfinyl group is responsible for the complete control of the n-facial selectivity in all these reactions.75 The Rh(II)-catalysed intramolecular 1,3-dipolar cycloaddition reaction of diazoamides (57) with alkenyl and heteroaromatic n -bonds yields pen-tacyclic compounds (59), via the ylide (58), in good to excellent yields and in a (g) stereocontrolled manner (Scheme 15).76... 

Numerous studies have dealt with different types of sulfur-containing hetero-dienophiles. Thus, hetero Diels-Alder reactions of N -sulfinyl dienophiles have been thoroughly studied by Weinreb et al. [454] the resulting cycloadducts represent useful and versatile intermediates in the synthesis of homoallylic amines [455] or pyrroles [456]. Further work using this type of S = N dienophiles... 

Sulfinylation of pyrrole" and thiocyanation of pyrrole" or of 1-phenylsulfonyl-pyrrole "" also provide means for the electrophilic introduction of sulfur, but at lower oxidation levels. 

Pyrrole and 1-methylpyrrole can be sulfinylated by sulfinyl chlorides or A-(phenyl-sulfinyl)succinimide. The products are prone to rearrange to the 3-isomers on contact with acid <80JOC5336>. A phenylsulfinyl group has been introduced at C3 of the indole ring by 3-sulfenylation of AT-lithioindole with diphenyl disulfide, followed by A-sulfonylation and oxidation to the sulfoxide <89JOCi782>. Sulfenylindoles can be oxidized to sulfones by MCPBA <93JMC1425>. 

The cycloaddition of 7V-sulfinyl compounds with dienes gives dihydrothiazine oxides, which are precursors of homoallyl amines or pyrroles. Reactions of these reactive dienophiles in the presence of SnCU or TiCU yield the adducts diastereoselectively under mild reaction conditions. 

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