Synthesis of hexasubstituted benzene derivatives from phloglucinol

Abstract

The synthesis of hexasubstituted benzene has been successfully performed by using phloroglucinol dehydrate as the starting material reacting with various acid chlorides (RCOCI; R = CH₃, Ph and C₇,H₁₅). The 1.3,5-triacy1-2,4,6-trihydroxy benzenc products were synthesized presumably through tripe O-acylation and then underwent Fries rearrangement to become tris(ortho-hydroxyaacyl) aromatic molecules ¹H-NMR spectroscopy suggested that the molecules were relatively flat induced by three strong intramolecular hydrogen bonds between the hydroxy groups and the adjacent carbonyl groups. The reaction with allyl bromide gave pentasubstituted benzene 68 in 35% yield. Compound 60 was modified into the ababab geometry by alkylations on the phenolic hydroxyl groups, giving compounds 69 and 71 in 65 and 18% yield, respectively. The addition on the ketone carbonyl was carried out by the reaction with phenylhydrazine yielding tris-hydrazone 72 in 18% yield. Compound 72 was found to form complexes with Fe(III) and Cu(II), evidenced by hypsochromic shift of the [Maximum wavelength]max of the complexes and the changes of the methyl and aromatic protons of the complexes relative to that of compound 72.