Abstract
The reaction of oximes of aromatic ketones with phenylacetylene in the presence of superbase systems (MOH-DMSO, where M = Li, Na, K) has been extensively studied for the first time. The effects of alkaline metal cation, the ketoximes structure and the reaction conditions (temperature, duration) on the products composition have been evaluated. Acetophenone oxime reacts with phenylacetylene (МОН-DMSO, where M = Li, Na, K, 140 о С, 6 h) to afford 2,5diphenyl-1H-pyrrole in 14-18% isolated yield. The reaction of benzylphenylketoxime with phenylacetylene (LiОН-DМSО, 120 о С, 12 h) delivers 2,3,4-, 2,3,5-triphenyl-1H-pyrroles (in 17% total yield) and 2,3,4-triphenyl-1-[(Z)-2-phenylethenyl]-1H-pyrrole (7% yield).
Highlights
A number of natural and synthetic pyrroles bearing aryl substituents possess high biological activity.[1,2] Currently, certain of the di- and triarylpyrroles are extensively employed as pharmaceuticals
The cholesterol reduction drug lipitor, one of the most commonly used in the United States, contains a 2,3-diphenylpyrrole motif.2а,3 A series of 2,3,4-triphenylpyrrole derivatives exert high hypoglycemic action and can be recommended for diabetes treatment.2а arylpyrroles are applied for the synthesis of fluorescent azaindacene dyes of BODIPY family[4] as well as optoelectronic materials,[5] it is their
Di- and triphenylpyrroles are normally prepared by condensation of 1,4-diketones with ammonia or ammonium acetate,[6,7,8,9] as well as by the reaction of 1,3-diketones[10,11] with different nitrogen-containing compounds followed by cyclization of the intermediates formed
Summary
A number of natural and synthetic pyrroles bearing aryl substituents possess high biological activity.[1,2] Currently, certain of the di- and triarylpyrroles are extensively employed as pharmaceuticals. Despite the satisfactory yields of the target products, the syntheses reported feature either hard availability of the starting materials[12] or multi-step procedures.[10]. The reaction of ketoximes with acetylene (the Trofimov reaction) in the superbase systems МОН-DMSO, where М = Li, Na, K, makes it possible to prepare a wide series of substituted pyrroles in one preparative step.[1,13] While this reaction is mostly studied with unsubstituted acetylene the applicability of phenylacetylene, an available substituted acetylene, still remains poorly understood.[14] the reaction of oximes of aromatic ketones with phenylacetylene could open a short-cut to pyrroles with several aromatic substituents. Apart from extension of the basic knowledge about the scope and limitations of the pyrrole synthesis from ketoximes and acetylenes it was hoped to elaborate one-step preparative protocols for the synthesis of as yet hardly accessible di- and triphenylpyrroles
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