Metal carbenoid mediated ring opening of furan-2-yloxy derivatives. Stereoselective synthesis of 2,4-hexadienedioic acid and 6-aryl-1-oxo-2,4-hexadienoic acid derivatives

2-Methoxy- and 2-trimethylsilyloxyfuran undergo facile ring opening reaction upon treatment with metal carbenoid. Treatment of 2-methoxyfuran with ethyl diazoacetate and aryl-α-diazocarbonyl compounds under metal catalysis afforded (2Z,4E)-hexadienedioate and 6-aryl-6-oxo-(2Z,4E)-hexadienoates respectively. When 2-trimethylsilyloxyfuran was used, desilylation occurred to give directly the monoprotected (Z,E)-muconic acid and 6-aryl-6-oxo-(2Z,4E)-hexadienoic acids.