The first tandem double palladium-catalyzed aminations: synthesis of dipyrido[1,2-a∶3′,2′-d]imidazole and its benzo- and aza-analogues

Abstract

A new strategy for the synthesis of the title compounds via a regio- and chemoselective one-pot inter- and intramolecular Buchwald-Hartwig amination of 2-chloro-3-iodopyridine with aminoazines and -diazines is reported.

Dipyrido[1,2-a;3′,4′-d]imidazole systems

“…Synthetic procedures for the construction of dipyridoimidazole motifs are very rare 10 and recent publications describe syntheses involving reaction of 2-aminopyridine derivatives with an appropriate dihalogenated pyridine system catalysed by palladium acetate or palladium acetate/copper (I) iodide in Buchwald-Hartwig type processes. 11,12 Alternatively, annelation of imidazo[1,2-a]pyridine systems has allowed the synthesis of some functionalised systems, albeit in low yield. 10,13,14 In all cases, further functionalisation of the heterocyclic core scaffolds to provide analogue systems has not been reported because, in part, the multi-step synthesis of functionalised dibrominated pyridine starting materials can be very difficult indeed.…”

Gold/Acid‐Co‐catalyzed Direct Microwave‐Assisted Synthesis of Fused Azaheterocycles from Propargylic Hydroperoxides

“…The heterocyclic core of tricycles 5 is of potential pharmacological relevance because of its intercalation ability with DNA. [14] The indole scaffold has been recognized as the fundamental nucleus for a large number of natural and synthetic products of biological significance. [15] Therefore, methods for the synthesis of new indole derivatives are highly appreciated.…”

Rapid synthesis of imidazo[4,5-b]pyridine containing polycyclics by means of palladium-catalyzed amidation of 2-chloro-3-nitropyridine

“…12 Finally, depending on the amide-containing heterocycle (monoor bicyclic compound), various imidazo pyridine-fused polycyclic compounds could be easily obtained in good yield. As typical examples given in Scheme 3, the preparation of the tricyclic imidazo pyridine 4h constituted an interesting 'umpolung approach' of the recently described 13 Buchwald reaction of 2-chloro-3-iodopyridine (instead of 1 in our method) and 2-aminopyridine (instead of 3-methoxypyridin-2(1H)-one (entry 8) in our example) leading to a common dipyrido imidazole system (compound 4h). Also, in another example involving an NH-amide bicycle (entry 9), the resulting tetracyclic compound 4i could be prepared in good overall yield.…”