Over the past few decades, furopyridines have emerged as key structural subunits prevalent in a number of natural products and structural analogues associated with interesting biological activities. Consequently, considerable efforts have been devoted to the synthesis of these fused heterocyclic scaffolds. This review covers the main methodologies reported in the literature for the preparation of furopyridines.

The furopyridine framework was chosen as a target for a lithiation study, in order to define the most effective conditions leading to the total functionalization of the heterocycle. Consequently, a detailed procedure for successive regioselective lithiations/electrophilic trapping of furo[3,2-b]pyridines is described and afforded several polyfunctionalized derivatives in good overall yields. A Pd-catalyzed cross-coupling reaction is also described and easily yielded the 7,7'-bifuro[3,2-b]pyridine.

Successive Regioselective Metalations of Fused Heterocycles: Synthesis of Polyfunctionalized Furo[3,2-b]pyridines. -A series of title compounds is synthesized using different lithiation methods. Only in one case functionalization at the 5-position is successfully achieved by conversion of chloro derivative (VIII) with hexachloroethane [cf. (IX)]. In contrast, treatment of chloro-derivative (VIII) with other electrophiles leads to Cl-Li exchange as is shown for silyl derivative (X). Moreover, silyl derivative (XII) gives silyl ether (XIII) instead of the expected furopyridine. Interestingly, bifuropyridine (VI) is obtained by C-C coupling of two furopyridines under usual Stille conditions. -(JASSELIN-HINSCHBERGER, A.; COMOY*, C.; CHARTOIRE, A.; FORT, Y.; J. Org. Chem. 78 (2013) 11, 5618-5626, http://dx.doi.org/10.1021/jo400748n ; HECRIN, SRSMC, CNRS, Univ. Lorraine, F-54506 Vandoeuvre-les-Nancy, Fr.; Eng.) -S. Adam 41-180

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