Synthesis and Characterisation of Some 2-[2(1-Phenyl-3-Thiophen-2-Yl-1h-Pyrazol-4-Yl)]-Vinyl Chromene-4-Ones

Abstract

ß-Diketone 5 is prepared by BakerVenkatram'an transformation of the ester 4, which is obtained by esterification of the acrylic acid 2 with 2-hydroxyacetophenone 3. The acid catalyzed cyclization of 5 yielded 2-[2(l-phenyl-3-thiophen-2-yl-l//-pyrazol-4-yl)]-vinyl chromene-4-one 6.

Hemicurcuminoids (1-styryl-1,3-diketones) – valuable multi-faceted building blocks for organic synthesis

“…Venkataraman et al used sodium amide in ester for this reaction; however in the later works potassium hydroxide in pyridine was more frequently used. 26–28 Conjugated (poly)enediones bearing an allyl substituent in the aromatic ring could be prepared using the t -BuOK/ t -BuOH system 29–31 or by using K 2 CO 3 in acetone 32 in good yields. The presence of two ortho -OH groups in the acetophenone molecule may lead to the formation of 3-cinnamoyl-2-styrylchromones 9 , bearing an enedione moiety, through double Baker–Venkataraman transformation and intramolecular cyclisation, which has been demonstrated by Waldvogel et al 33 by treatment of the corresponding ester with K 2 CO 3 in acetone under reflux.…”