I₂O₅-Mediated Iodocyclization Cascade of N-(1-Arylallyl)pyridine-2-amines with Concomitant C═C Bond Cleavage: A Synthesis of 3-Iodoimidazo[1,2-a]pyridines

Abstract

A facile method for the synthesis of 3iodoimidazo[1,2-a]pyridines has been successfully developed involving an I 2 O 5 -mediated iodocyclization cascade of N-(1arylallyl)pyridin-2-amines with concomitant CC bond cleavage. Preliminary mechanistic studies reveal that this protocol might undergo an oxidative cyclization/decarboxylation/iodination sequence in which I 2 O 5 is used as both an oxidant and an iodine source. The present protocol has advantages of wide substrate scope, simple operation, and metal-free conditions.

Transition‐Metal‐Catalyzed Carbohalogenative 1,2‐Difunctionalization of C−C Multiple Bonds

“…Instead, dehydration followed by two consecutive 1,2-iodine shifts pathway was postulated (Scheme 26). [41] This Au-catalyzed benzannulation-iodine transfer strategy was further extended in the synthesis of blue luminescent [7]helicenocarbazoles. Starting with symmetrical bis(indole)-1,3-diynes, diiodo-9H,9'H-1,4'-bicarbazoles were obtained by employing the previously optimized conditions.…”

“…Starting with symmetrical bis(indole)-1,3-diynes, diiodo-9H,9'H-1,4'-bicarbazoles were obtained by employing the previously optimized conditions. Subsequent Suzuki-Miyaura coupling with suitable boronic acids, the bis(iodocarbazoles) delivered final [7]helicenocarbazoles (Scheme 27). [42]…”

“…[2] Alongside construction of carbon-carbon bonds, the high abundance of carbon-halogen bonds as one of the most common functional groups present in wide range of natural products, [3] pharmaceutically active compounds, [4] agrochemicals [5] and molecules of material importance [6] and their synthetic utility as synthons in divergent complex molecular synthesis has attracted the organic chemists over the years to develop newer methodologies for straightforward generation of carbon-halogen bonds (Figure 1). Among the available protocols for carbon-halogen bond formation, synchronized to the numerous transition-metal-free strategies, [7] transition-metal-catalyzed selective CÀ X bond formation [8] in environmentally benign, operationally simple, atom and cost-effective manner has been an essential and challenging aspect of organic chemistry. [9] In the quest of atom and step economic access of highly functionalized organic molecules associated with the formation of new carbon-carbon and carbonheteroatom bonds, development of novel strategies for the efficient and straight forward difunctionalization of carbon-carbon multiple bonds have gained much popularity among the researchers from both academia and industry.…”

“…Plausible mechanism of Au-catalyze synthesis of iodocarbazoles via iodine-shift. Synthesis of[7]helicenocarbazoles.…”

Tungstate-Catalyzed Biomimetic Oxidative Halogenation of (Hetero)Arene under Mild Condition

“…13 C NMR (101 MHz,140.8,132.0,128.6,128.5,127.4,126.2,121.4,120.6,118.0,106.1 Methyl 2-amino-5-iodobenzoate (2-43) (Zhou and Song, 2018) was obtained as a brown solid (106 mg, 39% yield, 48% yield brsm; 28 mg starting material was recycled, 18% yield) according to General Procedure D for 17h. 13 C NMR (101 MHz, Chloroform-d) δ 167.3, 149.8, 142.2, 139.5, 118.8, 112.8, 75.9, 51.8 6-chloro-3-iodo-2-phenylimidazo[1,2-a] pyridine (2-47) (Zhou et al, 2019) was obtained as a yellow (172 mg, 97% yield) according to General Procedure D for 20 min. Product 2-47 was obtained (175 mg, 99% yield) without catalyst in a control experiment in 1h.…”