Six of new N-tert-butyl-N-substitutedbenzoyl-N-(2,4-dimethyl-2,3-dihydrobenzofuran)-7-carbohydrazide derivatives and five of new N-tert-butyl-N-substitutedbenzoyl-N-(5-methylchroman)-8-carbohydrazide derivatives were designed and synthesized from m-cresol. The synthesis highlighted that some kinds of reactions were ameliorated in methodology. An important feature is that 1-(3-allyl-2-hydroxy-4-methylphenyl)ethanone can easily be transformed into 1-(2,3-dihydro-2,4-dimethylbenzofuran-7-yl)ethanone just with concentrated sulfuric acid as catalyst. In addition, we found that 1-(5-methyl-2H-chromen-8-yl)ethanone could not be reduced to 1-(5-methylchroman-8-yl)ethanone directly by hydrogen with Pd/C as catalyst. It is an effective method for protecting 1-(5-methyl-2H-chromen-8-yl)ethanone with ethylene glycol to obtain 5-methyl-8-(2-methyl-1,3-dioxolan-2-yl)-2H-chromene and then reducing by hydrogen with Pd/C as catalyst to produce 1-(5-methylchroman-8-yl)ethanone in one step. Furthermore, SOCl2 can convert 2,3-dihydro-2,4- dimethylbenzofuran-7-carboxylic acid to 2,3-dihydro-2,4-dimethylbenzofuran-7-carbonyl chloride, but it is inefficient for transforming 5-methylchroman-8-carboxylic acid to the corresponding acyl chloride. Hence, different heterocycles on the benzene ring of benzoheterocyle moiety have influence on the reaction property of the corresponding acid.
Keywords: Dihydrobenzofuran, chroman, benzoheterocycle, diacylhydrazine, synthesis, insect growth regulator