- Unconventional Regiospecific Syntheses of Aromatic Carbonamides and Thiocarbonamides by Means of Tin-Mediated Friedel-Crafts Reactions
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Friedel-Crafts reactions of stannylarenes 1 with tosyl isocyanate (TsNCO, 2) give N-tosylcarbonamides 3 via ipso substitution of the stannyl group.Thus, unconventionally substituted aromatic carbonamides can be obtained.The combination of the reaction of 1 and 2 with that of 1 and chlorosulfonyl isocyanate (14) allows one-pot syntheses of N-(arylsulfonyl)-substituted aromatic carbonamides with optional substitution patterns on both aromatic rings.The known ipso-specific substitutions of stannylarenes with 14 are extended to bi- and tricyclic arenes as well as to thiophenes 6 and 22.One stannyl group can serve as a leaving group for two aromatic systems, as shown with diaryldialkyltins 29.Also, stannylalkanes such as 27 react with 14 to afford alkylsulfonyl isocyanates and products of further reactions, such as 28.From the reactions of 1 with ethoxycarbonyl isocyanate (32), ortho- and meta-substituted aromatic thiocarbonamides 33 which are potential precursors for further syntheses, are accessible.The scope, limitations, and mechanism of these electrophilic substitutions are outlined.
- Arnswald, Martin,Neumann, Wilhelm P.
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p. 7022 - 7028
(2007/10/02)
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- Mild and Efficient Synthesis of Aromatic Sulfonamides by in situ Preparation of the Corresponding Sulfonyl Isothiocyanates
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A new reaction between chlorosulfonyl isocyanate (1) and trialkylstannyl-substituted arenes 2a-k, 7, 9 is described.It provides the aromatic sulfonyl isocyanates 3 or their derivatives, the sulfonamides 4a-j, the sulfonylcarbamates 5a-b, or sulfonylureas 6, respectively.The trialkylstannyl group as an efficient leaving group allows mild reaction conditions to be applied and unusual substitution patterns to be obtained, normally not accessible by electrophilic aromatic substitutions.Thus, sulfonamidation can be achieved in meta position to a trifluoromethyl group. Key words: Electrophilic aromatic substitution; sulfodestannalytion; isocyanates, sulfonyl, aromatic; sulfonyl compounds; trialkylarylstannanes, application of
- Arnswald, Martin,Neumann, Wilhelm P.
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p. 1997 - 2000
(2007/10/02)
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