Synthesis of New Benzofuran-2-Carboxylic Acid Derivatives

Table 1

Cyclization of ethyl 6-methoxy-4-nitro-2-formylphenoxyacetate (4).

Trial	Molar ratio; Ester 4/K2CO3	Reaction time (h)	Product 2c; Yield (%)*
1	1 : 1	3	—
2	1 : 1	3.5	52
3	1 : 1	4	60
4	1 : 1.3	3	59
5	1 : 1.3	3.5	64
6	1 : 1.3	4	73

∗The yield was calculated relative to the starting ester 4.