Abstract
Sulfonyl-derived functional groups populate a broad range of useful molecules and materials, and despite a variety of preparative methods being available, processes which introduce the most basic sulfonyl building block, sulfur dioxide, using catalytic methods, are rare. Described herein is a simple reaction system consisting of the sulfur dioxide surrogate DABSO, triethylamine, and a palladium(0) catalyst for effective convertion of a broad range of aryl and heteroaryl halides into the corresponding ammonium sulfinates. Key features of this gas- and reductant-free reaction include the low loadings of palladium (1 mol %) and ligand (1.5 mol %) which can be employed, and the use of isopropyl alcohol as both a solvent and formal reductant. The ammonium sulfinate products are converted in situ into a variety of sulfonyl-containing functional groups, including sulfones, sulfonyl chlorides, and sulfonamides.
Highlights
Sulfonyl-derived functional groups populate a broad range of useful molecules and materials, and despite a variety of preparative methods being available, processes which introduce the most basic sulfonyl building block, sulfur dioxide, using catalytic methods, are rare
We have introduced the amine–SO2 charge-transfer complex DABSO [DABCO·(SO2)2] as a convenient and easy-tohandle solid which functions as a surrogate for SO2 gas in a number of known transformations,[10,11] and in a new palladium-catalyzed aminosulfonylation procedure using aryl halides.[12]
We have recently shown that aminosulfonamides, prepared from the palladium-catalyzed combination of aryl halides, DABSO, and hydrazines, can be converted into the corresponding sulfinates by way of a base-promoted degradation, the process is cumbersome in that it requires the initial introduction and expulsion of an expensive hydrazine derivative [Eq (2)].[17]
Summary
Sulfonyl-derived functional groups populate a broad range of useful molecules and materials, and despite a variety of preparative methods being available, processes which introduce the most basic sulfonyl building block, sulfur dioxide, using catalytic methods, are rare. Pioneering reports from Pelzer and Keim established that the palladiumcatalyzed introduction of SO2 was feasible, these early reports of sulfinic acid synthesis described reactions of poor scope and required high pressures of SO2 and hydrogen, and the use of inconvenient aryl diazonium substrates [Eq (1)].[9]
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