One-Pot Synthesis of 1-Iodoalkynes and Trisubstituted Alkenes from Benzylic and Allylic Bromides

Abstract

1-Iodoalkynes are formed in moderate to high yields from readily accessible benzylic and allylic alkyl bromides by a one-pot homologation/double elimination procedure with iodoform (CHI(3)). The developed conditions include facile purification and avoid the use of an excess of triphenylphosphine (PPh(3)), as described in classical Corey-Fuchs iodoalkynylation conditions. Replacing CHI(3) with CHI(2)Cl allows the isolation of the corresponding gem-(Z)-chloro-(E)-iodoalkene in good yield and stereoselectivity. Moreover, the use of benzhydryl bromides as nucleophiles enables the synthesis of trisubstituted alkenes under similar reaction conditions.

Acetic Acid Promoted Direct Iodination of Terminal Alkynes with N-Iodosuccinimide: Efficient Preparation of 1-Iodoalkynes

“…The controllable electrophilic and nucleophilic properties make them as dual functionalized molecules, bringing about numerous applications in chemical transformations. 1,2 Significant progress has been made in the development of synthetic approaches for the construction of 1-iodoalkynes, including iodination of metal acetylides (Scheme 1, path a), 3 iodination of propiolic acid/trialkylsilylacetylides (path b), 4,5 a two-step homologation/iodination or elimination sequence from aldehydes or benzylic bromides (path c) 6,7 and direct iodination of terminal alkynes (path d). 8 Among these methods, the direct iodination of terminal alkynes is the most appealing strategy.…”

Synthesis of 5-Iodo-1,2,3-triazoles from Organic Azides and Terminal Alkynes­: Ligand Acceleration Effect, Substrate Scope, and Mechanistic Insights

“…We found that ethynylbenzene is fully converted into (iodoethynyl)benzene within 20 minutes in the absence of an azide, under otherwise identical conditions. After filtering the reaction mixture through Celite 16 and removing the solvent, we recorded the 13 C NMR spectrum. The chemical shift of C* in the alkyne undergoes a large upfield shift, diagnostic of the formation of the 1-iodoalkyne (Table 4).…”

A Quaternary Ammonium Salt Promoted Regioselective Iodination of Terminal Alkynes: A Convenient Access to 1‐Iodoalkynes in Aqueous Media

“…Traditional methods for the synthesis of 1‐iodoalkynes includes the iodination of pre‐formed metal acetylides ( path A , Scheme ), direct iodination of terminal alkynes ( path B , Scheme ) and a two‐step homologation/iodination sequence from an aldehyde (Corey‐Fuchs reaction) or benzylic bromides ( path C , Scheme ). Alternatively, they can also be prepared by the direct iodination of trimethylsilyl‐protected alkynes or halodecarboxylation of propiolic acids ( path D , Scheme ).…”