Some reactions with ω‐bromoacetophenone: Synthesis of Δ^αβ‐butenolide and its transformation into pyrrole derivatives

Abstract

o-Bromoacetophenone reacts with the sodium salt of ethyl cyanoacetate to afford a-cyano-P-phenyl-A".Pbutenolide. This butenolide undergoes azo coupling with diazotized aromatic amines (ArNHJ to afford the hydrazo derivatives. These hydrazo derivatives (Ar= Ph, were transformed into the corresponding 3(2H)-pyridazinone derivatives on stirring in methanol in the presence of potassium hydroxide. These latter compounds were converted into the cowesponding 3-cyano-2,5-dihydroxy-4-phenyl-N-arylpyrrole derivatives on reduction with zinc dust in refluxing acetic acid, presumably via reductive cleavage of the N-N bond of the pyridazine followed by recyclization via loss of ammonia.In the context of our search for new simple syntheses of azoles, azines, and their fused derivatives [ 1-41 utilizing readily available starting materials, we have previously reported [5] that phenacyl thiocyanate (la) reacts with ethyl cyanoacetate (depending on the reaction conditions) to afford the Knovenagel condensation product 2a in relatively low yield (Scheme 1). In an attempt to improve the yield of 2a, we attempted to preDedicated to Prof Shigeru Oae on the occasion of hls seventyfifth birthda?To whom correspondence should be addressed

A novel synthesis of some new benzoyl‐substituted heterocycles from 2‐benzoyl‐3‐phenylpent‐2‐ene‐1,5‐dinitrile

“…Pyrroles and fused pyrrole derivatives represent an interesting class of heterocyclic compounds due to their synthetic and pharmaceutical importance and different approaches for their synthesis have been developed [10,11]. In the last few years we have reported several syntheses of pyrrole derivatives [12,13]. In the present work we explore the synthetic potentialities of 2a to obtain some novel N-substituted pyrroles and pyrrolofused pyridazine.…”

Phenacyl esters of acetic acid derivatives and their application for the synthesis of 2‐oxo‐4‐phenyl‐5‐(phenylhydrazono)‐2,5‐dihydro‐furan‐3‐derivatives

“…Only some of the compounds 4 are described in the literature as a very intensive dyestuff [5][6][7][8]. These compounds were prepared by reaction of diazonium salt 3 with furanone 2 (Scheme 1) [5][6][7][8].…”

“…These compounds were prepared by reaction of diazonium salt 3 with furanone 2 (Scheme 1) [5][6][7][8]. Since the compounds 2 have only one place for coupling with diazonium salt, the result is not surprising.…”

Phenacyl Bromides Revisited: Facile Synthesis of Some New Pyrazoles, Pyridazines, and Their Fused Derivatives

“…In the context of this program, we have previously reported several syntheses starting from 2‐bromo‐1‐phenylethanone (ω‐bromoacetophenone) 2a (obtained from acetophenone 1 by bromination; Fig. ) . Some new pyrrole, pyrazole, and pyridazine derivatives were required for such biological studies.…”