Chloroacetic acid reaction with salicylaldehyde

The analysis depicted for (64) reveals that the synthesis of benzofuran involves the conversion of salicylaldehyde into the corresponding aryloxyacetic acid by reaction with sodium chloroacetate in the presence of alkali, followed by heating with a mixture of acetic anhydride, acetic acid and sodium acetate (Expt 8.24). The ensuing cyclisation may be regarded as an internal Perkin reaction (Section 6.12.3, p. 1036) accompanied by a decarboxylative dehydration step. 

Condensation of salicylaldehyde and its derivatives with a variety of esters of chloroacetic acids in the presence of TBAB led to the synthesis of benzo[b]furans by means of a solid-liquid PTC reaction under the action of microwave irradiation [39]. This was a modification of one of the most popular routes to substituted benzo[b]furans, i.e. O-alkylation of O-hydroxylated aromatic carbonyl compounds with a-halogenated carbonyl compounds then intramolecular condensation. The mixture of aldehydes and chloroacetic acid esters were absorbed on potassium carbonate then irradiated in an open vessel in a domestic MW oven for 8-10 min (Eq. 26). 

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