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Polysubstituted furans were obtained with excellent yields via the electrophilic alkynylation of 1,3-dicarbonyl compoundsws with phenyl-or estersubstituted brominated alkynes. The reaction is catalyzed by the inexpensive and readily available catalyst, cobalt(II) chloride, and has a wide substrate scope. The C(sp) À C(sp 3 ) coupling occurs under mild conditions with short reaction times and does not require an inert atmosphere or ligands. It is proposed that the reaction proceeds through a chelation complex of cobalt(II) with the deprotonated 1,3-dicarbonyl compound.

Aw ide range of imidazo[1,2-a]pyridines are accessible from cheap and readily available 2-aminopyridines and 1,3-dicarbonyl compounds using au niqueC BrCl 3 /2-aminopyridine systemf or bromination at the a-carbon. 2-Aminopyridine is not only the substrate but also acts as abromination shuttle,t ransferringt he brominea tomf rom CBrCl 3 to the a-carbon of the 1,3-dicarbonyl.T he reaction mechanismi nvolvesaseries of reversible steps,i ncluding an addition reactionw ith cyclic transition state,t of orm ab romo-hemiaminal intermediate. Isolated yieldso fu pt o9 7% were obtained under mild conditions and at shortr eactiont imes in this transitionm etal-free,one-pot synthesis.

A versatile protocol for the synthesis of disubstituted 3-phenylimidazo[1,2-a]pyridines by coupling 2-aminopyridine with phenylacetophenones, phenylacetones, or β-tetralone has been developed. Isolated yields of up to 97% were obtained at 80 °C within 5 h. The 2-aminopyridine/CBrCl system acts as an α-bromination shuttle by transferring Br from CBrCl to the α-carbon of the carbonyl moiety. This triggers a series of steps with double C-N/C-N bond formation to the final product. The distinct advantages of this protocol include the use of commercially available inexpensive substrates, simplicity of a metal-free one-pot synthesis, and ease of scale-up to multigram quantities.

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