C-amidoalkylation of pyrroles with N-trifluoromethylsulfonyl and N-arylsulfonyl polychloroaldehyde imines

Abstract

N-(Trifluoromethylsulfonyl) and N-arylsulfonyl polychloroacetaldehyde imines reacted with pyrrole, 1-alkyl-, 1-benzyl-, and 1-(4-nitrophenyl)-substituted pyrroles, and bis-pyrroles to give the corresponding 2-[1-(sulfonylamino)polychloroethyl]-1H-pyrroles or mixtures of 2-and 3-[1-(sulfonylamino)polychloroethyl]-1H-pyrroles, depending on the nature of the Schiff base and substituent on the pyrrole nitrogen atom and reaction conditions. The first synthesis of 2,5-disubstituted NH-pyrrole by reaction of pyrrole with Schiff bases was described.We previously reported [1] on the reactions of 4-chloro-N-(2,2,2-trichloroethylidene)benzenesulfonamide with pyrrole and 1-methyl-1H-pyrrole and synthesized the corresponding 2-[2,2,2-trichloro-1-(4-chlorophenylsulfonylamino)ethyl]pyrroles as C-amidoalkylation products. The reactions occurred both in the presence of BF 3 · Et 2 O as catalyst and in the absence of it; in the latter case, the process required a longer time. The yield of the alkylation product from unsubstituted pyrrole did not exceed 37% [1]. We recently found [2] that pyrrole reacts with N-(2,2,2-trichloroethylidene)-trifluoromethanesulfonamide to give both 2-mono-and 2,5-disubstituted products.With a view to reveal relations between the structure of Schiff bases, their reactivity, and direction of their reactions with hetarenes [3], we continued our studies on reactions of pyrrole derivatives with Schiff bases containing strong electron-withdrawing groups. In the present work we examined reactions of pyrrole and N-substituted pyrroles with N-(2,2,2-trichloroethylidene)-and N-(2,2-dichloro-2-phenylethylidene)-trifluoromethane-and -arenesulfonamides. The products of these reactions are characterized by unique combination of a pyrrole ring and aminosulfonyl and trichloromethyl groups which undoubtedly determine their ability to undergo further chemical transformations and significance as potential biologically active substances. We previously demonstrated that (2,2,2-trichloro-1-sulfonylaminoethyl)-substituted indoles can be converted into N-substituted indolylglycines, which may be regarded as biologically active heteroauxin derivatives modified with a sulfonylamino group [4]. Obviously, analogous processes may be typical of structurally related pyrrole derivatives.Thus development of procedures for the introduction of amino(polyhalo)ethyl substituents into a pyrrole ring could open convenient synthetic approaches to new functionalized pyrroles as precursors of N-sulfonyl-substituted pyrrolylaminoacetic acids, aminocarbonyl compounds, and heterocyclic systems. The importance of this problem is beyond doubt.Schiff bases Ia-If were synthesized according to the procedures developed previously from the corresponding N,N-dichloro sulfonamides and trichloroethylene or phenylacetylene [5][6][7]. Schiff bases Ia-Ic were brought into reactions with pyrroles without isolation from the reaction mixture; reactions of Schiff bases Id-If with pyrroles were carried out in carbon tetrachloride. Pyrroles IIb-IIf were prepared by...