Carbonyl–Olefin Metathesis Catalyzed by Molecular Iodine

Abstract

The carbonyl−olefin metathesis reaction could facilitate rapid functional group interconversion and allow construction of complicated organic structures. Herein, we demonstrate that elemental iodine, a very simple catalyst, can efficiently promote this chemical transformation under mild reaction conditions. Our mechanistic studies revealed intriguing aspects of the activation mode via molecular iodine and the iodonium ion that could change the previously established perception of catalyst and substrate design for the carbonyl−olefin metathesis reaction.

Iodonium-Catalyzed Carbonyl–Olefin Metathesis Reactions

“…This was an issue for other catalytic systems, including Schindler's iron 6a,c and Tiefenbacher supramolecular 8 catalysts as well as our tropylium and molecular iodine catalysts. 9,10 This reduces lengthy and problematic product purification, which clearly is an advantage of using NIS and ICl to promote COM reaction in comparison to previously developed catalysts.…”

“…Most notable examples include Lambert's hydrazine 4 and Franzen's tritylium 5 catalysts, followed by Schindler's 6 and Li's 7 iron-catalyzed reactions and Tiefenbacher's supramolecular system. 8 Last year, our group reported the application of two new catalytic systems, namely tropylium ion 9 and molecular iodine, 10 to facilitate the COM reaction. Most important-ly, these catalysts were proven to be effective for all different types of COM reactions, including the intramolecular cyclization, the intermolecular metathesis, as well as the olefin ring-opening metathesis (Scheme 1).…”

Ring-opening carbonyl–olefin metathesis of norbornenes

“…At the present time, however, this area is still in its infancy, and the generality of available catalytic platforms falls far short of what would be needed to realize many of the potential applications of this reaction. Recent exciting developments in the use of organocatalysts, 8,9 Lewis acids, [10][11][12][13][14][15][16][17][18][19][20][21] and Brønsted acids 22,23 notwithstanding, this area requires breakthrough advances in catalyst and strategy design if it is to approach the levels of utility realized by other mature catalytic processes.…”

Interrupted Carbonyl‐Alkyne Metathesis

“…Ring-closing carbonyl-olefin metathesis between carbonyl and olefin functional groups has emerged as a powerful strategy for carbon-carbon bond formation ( Figure 1A). [1][2][3][4][5] Several Lewis acids have been identified for their ability to catalyze this transformation, including FeCl 3 , [6] GaCl 3 , [7] I 2 , [8] trityl [9] and tropylium [10] tetrafluoroborate salts, resulting in a variety of cyclopentenes, cyclohexenes, polyaromatic hydrocarbons, and functionalized pyrrolines. Lewis acid-catalyzed carbonyl-olefin metathesis reactions proceed via an initial [2 + 2]-cycloaddition to form intermediate oxetanes and a subsequent retro [2 + 2]cycloaddition to result in the desired metathesis products.…”