Sulfonates, from aryl sulfones

Koh, Y.J. and Oh, D.Y., A new synthesis of (f-ketophosphonates from aryl epoxy sulfones and dialkyl hydrogen phosphite, Tetrahedron Lett., 34, 2147, 1993. 

Apart from aryl esters and amides of carboxylic acids, aryl carbonates, and carbamates, other types of organic compound have been reported to undergo PFR. They include oxalates, formiates, sulfonates, sulfonamides, thioesters, selenoesters, and telluroesters. 

The Grignard reagents used in the reaction may be either those derived from aryl halides or those formed from alkyl halides. Phenyllithium reacted with the tosylate to give sulfones rather than azoxy compounds. 

Tosylates and other sulfonates and sulfates couple with Grignard reagents, most often those prepared from aryl or benzylic halides.Alkyl sulfates and sulfonates generally make better substrates in reactions with Grignard reagents than the corresponding halides (10-57). The method is useful for primary and secondary R. 

This reaction was first reported by Bucherer in 1906. It is the synthesis of carbazoles from aryl hydrazines, sodium bisulfite, and 1- or 2-naphthols (or 1- or 2-naphthylamines) and is generally known as the Bucherer carbazole synthesis or Bucherer reaction. In addition, the reaction between 2-aminonaphthalene-l-sulfonic acid and phenylhydrazine also gives carbazole, indicating that sulfonation of naphthylamine might be the early step in the reaction pathway. This reaction has been most commonly used hitherto for the preparation of dibenzocarboles. ... 

Apart from aryl halides, other very easily available substrates for nickel-catalysed biaryl (II) synthesis are aryl sulfonates (XII). Method D is very efficient in the homocoupling reactions of substituted aryl sulfonates in good to excellent yields [15], Table 6. Substituted aryl sulfonates are readily obtained from phenols and trifluoromethanesulfonic anhydride, benzenesulfonyl-, tosyl- or methanesulfonyl chloride in pyridine, or in a suitable inert solvent such as dichloromethane in the presence of triethylamine or Hiinig s base. Among other nickel complexes, Ni(dppe)Cl2 and Ni(dppf)Cl2 have been used (10 mo1%) as slightly less versatile catalysts for the homo-couplings of naphthyl sulfonates in refluxing THF, DMF or their mixtures [42]. 

Cobalt has attracted attention in recent years as a cost-effective and sustainable alternative to palladium or nickel. As indicated earlier, functionalized arylzinc reagents can be prepared from aryl halides and sulfonates by zinc insertion in the presence of catalytic amounts of CoBtj [50, 51, 210). Interestingly, the presence of this cobalt salt suffices to catalyze in situ the cross-coupling of the arylzincs thus produced with aryl, alkyl, and heteroaryl electrophiles such as organic halides [211-214] or thioethers, as exemplified with the formation of 286 [214] (Scheme 4.63). 

Protection of amino groups as azo compounds Sym. diaryls from aryl halides Replacement of sulfonic acid groups by hydrogen and partial replacement by hydroxyl... 

The reaction of sulfinates with alkynyl iodonium salts was successful, as these substrates are less easy to oxidize. Nevertheless, Waser and Chen demonstrated that EBX reagents can also be useful to synthesize alkynyl sulfones, as they allow a new one-pot procedure starting directly from Grignard reagents (Scheme 36) [161]. In this protocol, DABSO (DABCO-S02) is added after formation of the Grignard reagent. Addition of DME and TIPS-EBX 52 gives aryl alkynyl sulfones in 46-85% yield. Eor base sensitive substrates, it was also possible to start from aryl iodides and use a palladium catalyst. 

In aromatic sulfones, sulfonamides, and sulfoxides with electron-donating substituents in the ortho, meta, and para position, the sulfur-containing group was displaced by a cyano group on irradiation in a t-BuOH/aqueous solution of KCN (see Scheme 4.19). The yields of photosubstitution products deaeased on passing from aryl sulfones to aryl sulfoxides and followed the order para > ortho > meta. [118-120] Analogously, when dichloroanilines were used as the substrates, the corresponding dicyano derivatives were obtained [120]. 

Progress has been made in extending the Suzuki reaction from aryl triflates, to other less reactive aryl sulfonates, which show poor reactivity towards oxidative addition to Pd(0). A recent approach to this problem involves the activation of 1 triflates by complexation of electron-withdrawing Cr(CO)3 to the arene moiety (144). 

Preparation from Aryl Halides and Sulfonates by Cross-coupling... 

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