TIN FOR ORGANIC-SYNTHESIS .10. UNCONVENTIONAL REGIOSPECIFIC SYNTHESES OF AROMATIC CARBONAMIDES AND THIOCARBONAMIDES BY MEANS OF TIN-MEDIATED FRIEDEL-CRAFTS REACTIONS

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 isothiocyanate (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.