Example 1 Preparation of 2-methoxythiophene: In a reactor, 300 g of 2-bromothiophene (1.84 mol), 2.64 g of copper(I) bromide (CuBr, 1 mol%), 18.4 g of polyethylene glycol dimethyl ether (PEG DME 500, 2 mol%), and 660 g of a methanolic solution of sodium methanolate (30% concentration, precursor concentration of 30.6%) were added in sequence. The mixture was heated to 90 °C for the reaction and the progress of the reaction was monitored by gas chromatography (GC) until the conversion was >98% (total reaction time 8h). Upon completion of the reaction, the reaction mixture was slowly poured into 500 g of water and filtered through Decalite. Subsequently, the aqueous phase was extracted twice with methyl tert-butyl ether (MTBE, 150 g each time). The organic phases were combined and purified by vacuum fractional distillation to give a final 182 g of 2-methoxythiophene (1.59 mol, 86.4% yield) with a GC purity of >99% (% area).
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