Efficient synthesis of 1-iodoalkynes via Al₂O₃ mediated reaction of terminal alkynes and N-iodosuccinimide

Abstract

An efficient Al2O3-mediated direct iodination of terminal alkynes was developed to afford 1-iodoalkynes.

γ-Aluminum Oxide-Mediated Iodination of Terminal Alkynes

“…As it was already shown in our recent work, [32] the iodination of phenylacetylene (1a) with N-iodosuccinimide (NIS) in the presence of neutral γ-aluminum oxide could produce 1-(iodoethynyl)benzene (3) in high yield (98%) (Scheme 1). When 2.4 equiv.…”

“…The mono-iodination of terminal alkynes in our previous work were carefully investigated. [32] Therefore, we devoted our efforts to the tri-iodination of terminal alkynes by varying the amount of iodine and the temperature of the reaction (Table 1). As shown in Table 1, the best conditions for the second step were the treatment of the reaction mixture of the first step with 1.…”

“…Besides, those selective iodinations did not occur without the activation of γ-Al 2 O 3 . [30][31][32] Although the specified mechanism for Al 2 O 3 mediated iodination reaction remains unclear, the should play a crucial role via activating the NIS and I 2 and influencing the chemoselectivity and yield of this new process.…”

“…Very recently, we have described the aluminum oxide-mediated iodination of terminal alkynes with N-iodosuccinimide to produce 1-iodoalkynes in moderate to high yields. [32] Based on this protocol, herein, we further evaluate the tri-iodination of terminal alkynes with the activation of γ-aluminum oxide and present an efficient approach for the preparation of 1,2,2-triiodovinyl derivatives in high yields via twice iodination of terminal alkynes.…”

Co-operative halogen bonds and nonconventional sp-C—H...O hydrogen bonds in 1:1 cocrystals formed between diethynylpyridines and N-halosuccinimides

“…Hypervalent iodine sources have also been used, as have oxidants, as co- ISSN 2053ISSN -2296 reactants (Liu et al 2017). Amongst the milder methods reported, several have focused on the application of N-iodosuccinimide in acetic acid (Yao et al, 2020a), with -alumina (Yao et al, 2020b), and in acetone with silver nitrate as catalyst (Hofmeister et al, 1984). Herein we report the unexpected isolation and characterization of the unreacted 1:1 cocrystals formed on rapid evaporation of mixtures of the diethynylpyridines 2,6-diethynylpyridine (26DEP) and 3,5-diethynylpyridine (35DEP), and the N-halosuccinimides N-bromosuccinimide (NBS) and N-iodosuccinimide (NIS) in acetone (Scheme 1).…”