An efficient tandem process for the selective synthesis of 1,2‐annulated α‐fused quinoxalines using benzotriazole methodology by a modified Pictet–Spengler reaction is described. The approach involves the reaction of arylamines 4 with aromatic aldehydes 5 to furnish 6‐endo‐dig‐cyclized products. Dihydroquinoxalines 6 were selectively obtained by using AlCl3 in tetrahydrofuran (THF) at room temperature for two hours. However, after ten hours, quinoxalines 7 were obtained exclusively in excellent yields. A series of biologically important fluoro‐ and piperazenyl‐substituted quinoxalines were also synthesized. This developed methodology also provides access to a novel tandem synthesis of quinoxalinones 9.

Iodine has been recognized as an efficient, non-toxic, readily available and easy-to-handle electrophilic reagent to favour halocyclization reactions for the synthesis of novel iodofunctionalized heterocyclic molecules that serve as versatile intermediates in synthetic organic chemistry. This review presents numerous useful methodologies for the synthesis of O, N, S, and Se-heterocycles through electrophilic cyclization via the attack of an electrophile on the C(sp) bond of alkynes. The cyclization proceeds under mild reaction conditions and tolerates a wide variety of functional groups.

Synthesis of carbazoles using indoles as precursors through CH activation/annulation.

An efficient strategy for the synthesis of pyrrolo[1,2-a]quinolines and indolizines from pyranoquinolines via site-selective electrophilic cyclization and subsequent opening of pyran ring using silver/iodine under mild reaction conditions is described. This approach involves the preferential attack of the pyridyl nitrogen over aryl ring and leads to the formation of 5-endo-dig cyclized products. Quantum chemical calculations between C-N (ΔE(a) = 9.01 kcal/mol) and C-C (ΔE(a) = 31.31 kcal/mol) bond formation were performed in order to rationalize the observed site selectivity. Structure of the products were confirmed by the X-ray crystallographic studies. Iodo-substituted compounds generated by the electrophilic iodocyclization were further diversified via Pd-catalyzed cross-coupling reactions.

The fusion of fluorine in drug molecules through different fluorinating reagents remains a cornerstone in pharmaceutical chemistry. Progress in the field of deoxyfluorination through the development of novel reagents has...