G. Reddy, K. Rao
2006
Citations
0
Influential Citations
4
Citations
Journal
Heterocyclic Communications
Abstract
A simple and rapid synthesis of 4//-4-oxo-l-benzopyran-3-yl (4a-h) and 1,3-diarylpyrazol4-yl propanoic acids (5a-h) using Meldrum's acid (1) from the corresponding carboxaldehydes (2 & 3) is reported herein. Introduction A variety of pharmacological activities such as antifungal, antibacterial and anticoagulant activities have been reported for benzopyrans. 4-Oxo-l-benzopyran-3-carboxaldehydes are versatile intermediates and found their application in the synthesis of a variety of heterocycles bearing benzopyranone system and also functionalized benzopyranones'. These compounds undergo condensation reaction with active methylene compounds such as dimedone, malonic acid and phenylacetic acids forming the corresponding methylene derivatives. Pyrazole ring constitutes an important pharmacophore in a number of biologically active molecules. In view of their medicinal importance the synthesis of functionalized benzopyrans and pyrazoles is a subject of interest to many organic chemists. Recently some propanoic acids have been reported useful in the treatment of diabetes mellitus, hyperlipidemia impaired glucose tolerance, inflammatory diseases and arteriosclerosis. Meldrum's acid (2,2-dimethyl-4,6-dioxo-l,3-dioxane) is a versatile synthon with remarkable activity and is of tremendous use in organic synthesis. Araldehydes react with this in the presence of triethylamine-formic acid adduct to give arylpropanoic acids. However, this method has received little attention in the synthesis of heteroaryl propanoic acids. A lone example for the synthesis of benzopyran-3-yl propanoic acid was reported by Nohara et. al by refluxing benzopyran-3carboxaldehyde with malonic acid in pyridine at 110°C followed by hydrogenation of the corresponding benzopyranyl acrylic acid at 90°C using palladium black as catalyst. Where as pyrazol4-yl propanoic acid was prepared by Na-Hg reduction of the corresponding unsaturated ac id" . However, the reported methods for the synthesis of benzopyranyl and pyrazolyl propanoic acids involve multi steps and use of expensive reagents in the reduction step. In continuation of our work on library synthesis of various substituted benzopyrans and pyrazoles' we report herein a simple one step synthesis of title compounds using Meldrum's acid. (Scheme-1) Vol. 12, No. 6, 2006 A simple and rapid synthesis of 4H-4-oxo-l-benzopyran-3Yl and 1,3-diarylpyrazol-4-yl propanoic acids