A selective synthesis of 4-bromo-2-furancarboxaldehyde and its pinacolborane derivative

Abstract

A selective synthesis of ethylene acetal of 4-bromo-2-furancarboxaldehyde (4) and its pinacolborane derivative (5) is described. The synthesis was carried out using 2-furancarboxaldehyde (1) that was brominated to 4,5-dibromo-2-furancarboxaldehyde (2) in an emulsion of aluminum chloride and methylene chloride. The product was isolated, protected as ethylene acetal, and selectively debrominated to the ethylene acetal of 4-bromo-2-furancarboxaldehyde (4) in one step. This moiety was reacted with pinacolborane to give a reactive reagent of Suzuki coupling.

Perspectives on the synthesis and use of ageladine A

“…The Pictet-Spengler reaction uses 2-acetyl-aminohistamine [8] and 4,5-dibromo-1-SEM-pyrrol-2-carb-aldehyde [9] synthesized in a two-step synthesis starting with the bromination of pyrrol-2-carbaldehyde 25,26 and protection with trimethylsilylethoxymethyl chloride (SEMCl) 15. . This protecting group revealed itself as the most stable during the subsequent reactions steps and makes the chromatographic procedures easier, compared to the Boc-group.…”