A New Synthesis and Application of 1-Aryl-2,4-diones

Abstract

Methyl ketones or ethyl acetate react with aromatic abromo ketones in the presence of two equivalents of tert-butoxyor diethylaminomagnesium bromide in benzene (toluene) under reflux to produce 1-aryl-2,4-diones. The conversion, apparently, occurs via aldol condensation and subsequent [1,2]-sigmatropic rearrangement of the intermediate 3-bromo-2-hydroxy ketones. A number of fused aromatic and heteroaromatic phenols have been prepared by cyclodehydration of 1-aryl-2,4-diones.

The Chemistry of α-Haloketones and Their Utility in Heterocyclic Synthesis

“…The condensation of phenacyl halides with aldehydes has been used for the preparation of oxiranes 303 . The reaction proceeds via the cross aldol condensation mechanism ( Scheme 88 ) [ 549 , 550 , 551 , 552 , 553 , 554 , 555 ].…”

Synthesis of aromatic heterocycles

“…31 6-Hydroxybenzothiophenes have been synthesised by a procedure in which the benzene ring is annelated to a 2-substituted thiophene by acid catalysed cyclisation. 44 4-Chloro-1,2,3-dithiazole-5-thione, which is readily prepared from 4,5-dichlorodithiazolium chloride (Appel's salt) and hydrogen sulfide, reacts with diphenyldiazomethane to give the benzothiophene 35 by way of the isolable intermediate 34 In a continuation of their work on benzo[c]thiophenes, Cava and his group have described a synthesis of the bis(2-thienyl)-benzo[c]thiophene 36 from the phthalide 37. 46 They have also described a much improved synthesis of naphtho[2,3-c]thiophene 38 which makes use of a base catalysed Pummerer reaction.…”

The Chemistry of α‐Haloketones and Their Utility in Heterocyclic Synthesis

“…The condensation of phenacyl halides with aldehydes has been used for the preparation of oxiranes 303. The reaction proceeds via the cross aldol condensation mechanism (Scheme 88) [549][550][551][552][553][554][555]. Regiospecific cross aldol-type condensation have been demonstrated by the simultaneous addition of α-haloketones and aldehydes or ketones to a mixture of diethylaluminum chloride and zinc [556][557][558], or by means of Bu 3 SnAlEt 2 complex [559][560][561], titanium(II) chloride [562], Co(0) [563], Sm(II) [564], In(0) [565], CrCl 2 [566] or cobalt(0) trimethylphosphine complex [567,568] to give similar results of the kinetic crossed aldol products 305 (Scheme 89).…”