The reaction of 2-aminopyridines or 2-aminothiazole with N-(2,2-dichloro-2-phenylethylidene)arensulfonamides affords the corresponding products of nucleophilic addition to the azomethine group, N-[2,2-dichloro-2-phenyl-1-(heterylamino)ethyl]sulfonamides, in good yields. The latter are easily cyclized to (imidazo[1,2-a]pyridin-3-yl)sulfonamides and (imidazo[2,1-b]thiazol-5-yl)sulfonamides in the presence of [a] A.E. 369 Scheme 4. A tentative route for the formation of imidazo[1,2-a]pyridines 5.www.eurjoc.org

N-(1-Aryl-2-polychloroethyl)arenesulfonamides obtained on the basis of N,N-dichlorosulfoamides and polychloroethenes or phenylacetylene undergo a reaction cascade in the presence of mercaptoethanol. The reaction cascade opens a new route to the series of cyclic or open-chain sulfonamide derivatives. The process includes cyclization to aziridine intermediates, their further recyclization, and isomerization to imidoylchlorides or chloroimines, followed by substitution or reduction under the action of mercaptoethanol or hydrolysis. The final sulfonamide structures depend on the starting N-(polychloroethyl)sulfonamides. N-(2,2-Dichloroethyl)sulfonamides were transformed into sulfonamide-containing 1,4-oxathians while N-(2,2,2-trichloroethyl)sulfonamides were converted to N-(2-arylacetyl)arenesulfonamides. N-(2-Phenyl-2,2-dichloroethyl)sulfonamides form enamide derivatives that were transformed into aromatic ketones.

The reaction of 2‐aminopyrimidines with N‐(2,2‐dichloro‐2‐phenylethylidene)arenesulfonamides affords the corresponding products of nucleophilic addition to the azomethine group, N‐[2,2‐dichloro‐2‐phenyl‐1‐(heterylamino)ethyl]sulfonamides, in good yields. The latter are easily cyclized to give imidazo[1,2‐a]pyrimidin‐3‐ylsulfonamides in the presence of NaOH, whereas the expected isomeric imidazo[1,2‐a]pyrimidin‐2‐ylsulfonamides are not formed. A tentative mechanism for the formation of annulated heterocyclic derivatives through Dimroth rearrangement has been proposed.

Abstract2‐Phenyl‐3‐(sulfonamido)benzofurans are produced in a cascade reaction of N‐(2,2‐dichloro‐2‐phenylethylidene)arenesulfonamides with para‐substituted phenols in the presence of the superacid H2SO4/P4O10 system.

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