Novel aspects in the synthesis and acid-promoted cyclisation of some 2-diazo-2′-(p-tolylsulphonylamino)acetophenones: electrophilic displacement of an arylsulphonyl group from a sulphonamide

Abstract

Under conditions where 2-(p-tolylsulphonylamino)benzoyl chloride (VIa) and diazomethane gave the expected diazo-ketone (VIIIa) in high yield, use of diazoethane gave only a low yield of the corresponding diazopropiophenone (VIIIb), contaminated by 2-methyl-N-(p-tolylsulphonyl)indoxyl (Xa). In contrast, 2-(N-methyl-p-tolylsulphonyl)benzoyl chloride (VIb) reacted with both diazoalkanes to give high yields of the expected diazoketones (VIIIe and f). 2-Diazo-2′-(N-methyl-p-tolylsulphonylamino)acetophenone (VIIIe) in acetic acid–acetic anhydride provided 3-acetoxy-2-acetyl-1-methylindole (XII) and toluene-p-sulphonic acid via novel electrophilic displacement of an arylsulphonyl group from the sulphonylamino-substituent; similar displacement from 2-diazo-2′-(p-tolylsulphonyloxy)acetophenone (Ih) was much more difficult.