5-Substituted-2-furaldehydes: a synthetic protocol utilizing an organozinc route.

Facile synthetic routes for the preparation of a wide range of 5-substituted 2-furaldehydes have been revealed. They were accomplished through either Pd-catalyzed cross-coupling reaction of various aryl- and heteroarylzinc halides with 5-bromo-2-furaldehyde or utilization of a new organozinc reagent, 5-(1,3-dioxolan-2-yl)-2-furanylzinc bromide, which was easily prepared by the direct insertion of highly active zinc to 2-(5-bromofuran-2-yl-1,3-dioxolane. Of special note is the uniqueness of using a new organozinc reagent, representing a first example of the direct synthesis of the corresponding organozinc halide. The subsequent coupling reactions in various types of reaction conditions led to the formation of somewhat different furan derivatives. It is also of significance that all of the cross-coupling reactions were carried out under mild conditions.