BENZO[d]OXAZOLE DERIVATIVES FUNCTIONALIZED WITH REACTIVE GROUPS

Abstract

A series of compounds having a benzoxazole moiety in their structure have been synthesized starting from 6-hydroxy-2-methylbenzo[d]oxazole, whose preparation through the Beckmann rearrangement of resacetophenone oxime is described. First, substitution with bromine and chlorine of the aforementioned heterocyclic phenol using molecular bromine and N-chlorosuccinimide was shown to lead to the corresponding 5,7-dibromo-6-hydroxybenzo[d]oxazole and 5,7-dichloro-6-hydroxybenzo[d]oxazole, respectively. Next, these substrates were O-alkylated with 4-vinylbenzyl chloride, allyl bromide and propargyl bromide with a view of obtaining potential monomers that feature a benzoxazole moiety in their structure. In addition, O-alkylation of these hydroxybenzoxazoles with methyl bromoacetate afforded the related heteroaryloxyacetic esters, which could be considered as an entry toward carboxylic acid derivatives carrying a benzoxazole fragment. Furthermore, benzaldehydes and acetophenones bearing a benzoxazole ring system were obtained through the reaction of these hydroxybenzoxazoles with 3-chloromethyl-4-methoxybenzaldehyde and 3-chloromethyl-4-methoxyacetophe­none. Also, a pyrazoline–benzoxazole hybrid was synthesized from 6-hydroxy-2-methylbenzo[d]oxazole and a pyrazoline with a bromoacetyl substituent at N¹.