Abstract

Y. L. N. Murthy¹, K. Srihari Varma² and CH. V. V. Satyanarayana Murthy²

Resorcinol (1) was acylated using acetic acid in the presence of fused ZnCl2 at 140-1500 C for 15 min with stirring. The reaction mixture is left for 1hr and then 100ml of 1:1 HCl was added to break the zinc chloride complex and within 5 minutes precipitation commenced. The precipitate was washed with very dilute HCl and water. A red precipitate was obtained; which was crystallized from 20% HCl to give resacetophenone (II) needles and characterized by comparing its spectral data (IR, NMR) with those reported in literture m.p. 145°C. Ahluwalia et al1 reported the synthesis of 2, 2-dimethyl chromans in very good yield by condensing polyphenol derivates with isoprene in presence of orthophosphoric acid as catalyst. In our attempts to modify the reaction conditions, PPA was found to be a better condensing agent compared to orthophosphoric acid to result in a more or less homogenous reaction mixture leading to the cyclic chroman derivatives in very good yields.2 A solution of Isopene in xylene was added dropwise during 8 hours to a mixture of resacetophenone and PPA in xylene with constant stirring at 30-35°C. Stirring was continued for further 1 hour. The reaction mixture was taken into reduced pressure to give a pale yellow gummy material. This on column chromatography over silica gel yielded the chroman in hexane / ethyl acetate cluates (96:4) and the unreacted resactophenone from hexane / ethyl acetate eluates. The resacetophenone (II) on nuclear prenylation2,3 with isoprene in the presence of PPA at room temperature resulted the formation of 2, 2-dimethyl-6-acetyl-7-hydroxy chroman (III) in 63% yield. (III) crystallized as colourless needles. The chroman (III) on condensation with substituted and unsubstituted benzaldehydes in the presence of 30% alcoholic alkali4 at room temperature resulted the formation of chalcone derivatives in good yield (85%). The thin layer chromatography (TLC) of these chalcones showed characteristic colours with methanol – sulphuric acid (9:1) as a spraying reagent. They also exhibited the characteristic colour test with antimony trichloride5. With the above procedure, compound (IV) was synthesized.

Synthesis; pyrimidine derivatives antimicrobial activity

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