1,4-Diazabicyclo[22.2]octane Bis(sulfur dioxide) adduct (DABSO)

Abstract

(A) By analogy with already established carbonylation chemistry, 2a Nguyen and co-workers2b have demonstrated that it was possible to develop palladium-catalyzed reactions to combine aryl halides, sulfur dioxide and N-nucleophiles. They have shown for the first time that is possible to prepare C-SO2-N linkages by an aminosulfonylation process using palladium catalysis. With DABSO, the authors achieved aminosulfonylation reactions between a range of aryl iodides and N,N-dialkylhydrazines, providing aryl N-dialkylaminosulfonamides in good to excellent yield (57-93%). (B) Emmet and co-workers3 have shown that DABSO can effectively replace sulfur dioxide gas in a novel palladium-catalyzed aminosulfonylation process. For example, 4-iodotoluene and Naminomorpholine in the presence of DABSO, cesium carbonate, t-Bu3P, Pd(OAc)2 and DABCO in dioxane, yielded the sulfonylhydrazide in 93% yield. Aryl bromides were employed, too, albeit resulting in lower yields. In this report, the authors have extended the scope of the palladium-catalyzed couplings of DABSO with alkenyl and heteroaryl iodides. In addition, other N-nucleophiles could be used. C) Woolen et al. 4 have studied the formation of sulfonamides, sulfamides, and sulfolenes. They have demonstrated that DABSO can effectively replace gaseous sulfur dioxide in a number of established processes. One of them consists of preparing sulfonamides from DABSO with aryl Grignard reagents, followed by treatment with sulfuryl chloride and an amine, to afford sulfonamides in good yield. In another example, when DABSO was combined with various anilines and iodine, the authors successfully synthesized several N,N′- diphenylsulfamides in 63% yield. They finally established that cheletropic addition of DABSO with 2,3-dimethylbutadiene gives access to sulfolene in 80% yield. (D) Ye et al.5 have developed a novel and efficient route to aryl Naminosulfonamides via a palladium-catalyzed three-component coupling of arylboronic acids, sulfur dioxide and hydrazines in presence of dioxygen. Initially, they studied the palladium-catalyzed reaction of 4- methylphenylboronic acid and N-aminomorpholine in the presence of DABSO. Once the ligand, base, solvent and temperature were optimized, they examined a wide range of arylboronic acids and amines under these conditions (E) Waldmann et al.6 have shown that a bromine-lithium exchange with various aryl halides, followed by addition of DABSO, yields an aryl sulfinate. The authors used DABSO as an alternative SO2 source in the reaction mixture. With this methodology, they explored a novel application in the synthesis of aryl sulfonamides toward one-pot sequences. © Georg Thieme Verlag Stuttgart. New York.