Fluorobenziodoxole−BF₃ Reagent for Iodo(III)etherification of Alkynes in Ethereal Solvent

Abstract

A combination of fluorobenziodoxole (FBX) and BF3 ⋅ OEt2 in cyclopentyl methyl ether promotes regio‐ and stereoselective addition of benziodoxole and methoxy groups to alkynes. This difunctionalization reaction tolerates a variety of functionalized internal and terminal alkynes to afford trans‐β‐alkoxyvinylbenziodoxoles, which represent versatile precursors to stereochemically well‐defined multisubstituted vinyl ethers. The reaction is proposed to involve cleavage of the I−F bond of FBX by BF3, followed by electrophilic activation of the alkyne by the resulting cationic IIII species that triggers the nucleophilic addition of the ethereal oxygen.

Ritter-type iodo(iii)amidation of unactivated alkynes for the stereoselective synthesis of multisubstituted enamides

“…Recently, we reported a trans -iodo( iii )etherification reaction of alkynes with BXT and alcohol or with BF 3 -activated fluorobenziodoxole (FBX) and dialkyl ether, which allowed for the stereoselective synthesis of multisubstituted vinyl ethers. 17 During this study, we failed in engaging primary and secondary amides as nucleophiles in place of alcohol, observing no desired enamide product. Given this result, we turned our attention to the use of nitrile and water to achieve the putative iodo( iii )amidation.…”

“…The magnitude of these bond orders, along with the geometry of the bent alkyne in the TS as revealed by the bond angles, illustrates that the C–I( iii ) bond formation is intrinsically much earlier than the C–N bond formation. Given this nature of the iodo( iii )functionalization TS, 17 it appears reasonable that the sterically undemanding nitrile nucleophile has preference toward the addition to the more hindered acetylenic carbon so that the steric repulsion between the bulky BX and t Bu groups can be minimized. The entire energy profile for the reaction between 4,4-dimethylpent-2-yne, BXT, and MeCN is provided in the ESI, † which supports kinetic control of the regioselectivity of the reaction.…”

Organohypervalent heterocycles

“…C-VBXs can be easily synthesized by coupling vinylboronic acids and suitable hypervalent iodine compounds, [511][512][513][514] whereas several synthetic methods have been reported recently for the synthesis of 'X-VBXs' through the addition reaction of S-, N-, O-, and Xnucleophiles to ethynylbenziodoxoles (EBXs). [515][516][517][518][519][520][521][522][523][524] A common approach for the preparation of X-VBXs starting from EBXs is outlined in Scheme 44.…”

Exploring New Reactions and Syntheses of Trivalent Iodine Compounds

“…26 Motivated by the general challenge of alkyne difunctionalization and inspired by Ochiaiʼs reagent system, we found that a combination of uorobenziodoxole (FBX) and BF 3 ･OEt 2 promotes iodo(III)etheri cation of alkynes in ethereal solvent (Scheme 16). 27 The reaction of 1─ phenyl─ 1─ propyne in diethyl ether afforded a β ─ ethoxy vinylbenziodoxole (VBX), while a β ─ methoxy analogue was obtained from the reaction performed in cyclopentyl methyl ether. By analogy with Ochiaiʼs system, BF 3 was assumed to abstract the uoride from FBX to generate a BX cation, which would then activate the alkyne.…”