AuCl₃‐Catalyzed Ring‐Closing Carbonyl–Olefin Metathesis

Abstract

Compared with the ripenesso fo lefin metathesis, exploration of the construction of carbon-carbon double bonds through the catalytic carbonyl-olefin metathesis reactionr emainss tagnant and has received scant attention. Herein, ah ighlye fficient AuCl 3 -catalyzed intramolecular ring-closing carbonyl-olefin metathesis reaction is described. This method features easily accessible starting materials, simple operation,good functional-group tolerance and short reaction times, and providest he target cyclopentenes, polycycles, benzocarbocycles, and N-heterocycle derivatives in good to excellent yields.Carbon-carbon double-bond formation is one of the useful and fundamentalr eactions in synthetic organic chemistry,p articularly in the synthesis of complex natural products, bioactive molecules, synthetic drugs, and functional organic materials. [1] Generally,c onventional wisdom states that the construction of the carbon-carbond ouble bond mostly relies on the olefination of carbonyl compounds ando lefin metathesis. Since the pioneering work by Wittig, Horner,a nd Emmons,t he synthesis of alkenes by the olefination of carbonyl compounds has evolveda so ne of the most efficient methods, whichu ses phosphorus, sulfur,a nd silicon ylides as highly polarizedn ucleophilic components to add to carbonyl derivatives. [2] Olefin metathesis is another more important approach to obtain olefins andh as brought about ah uge development of many applicationsi ns ynthetic organic chemistry,s ince the discovery of second-generationc atalysts consisting of well-defined metalcarbene complexes, which are mostly based on stable molybdenum or ruthenium. [3] Compared with the ripenesso fo lefin metathesis and Horner-Wadsworth-Emmons reactions, other double-bond metathesis reactions are much less developed, [4] but these metathesis reactions should hold great potential for complex molecular synthesis through one-step synthetict ransformation.Amongt hem, the hitherto elusive carbonyl-olefin metathesis may be the mostp owerful alternative to have appeared in some applications for the total synthesis of naturalp roducts and construction of complex molecules, as usually these molecules are difficult to synthesis by other methods. [5] However, the historical early reports based on photoinduced, stoichiometrica mounts of transition-metal-promotedand even metalalkylidene-mediated carbonyl-olefin metathesish ampered the practicality because of limitations for substrates bearing chromophores, harsh reaction conditions, competing polymerization,h igh cost, and environmental pollution. [6] The fundamental cause of the stagnancy aboutc arbonyl-olefin metathesis lies in:1 )the difficulties in establishing ac atalytic version due to the formation of ak inetically inert metal-oxo complex duringt he cycloreversion step;2 )potential side reactions such as polymerization, ene reaction, alkylation, and Prins reaction etc.;3)regenerationofs tartingc arbonyl-olefinpairs.Recently,t he real breakthrough has begun to dawn because of strategies and catalysts, such...

Hydrogen Bonding Networks Enable Brønsted Acid-Catalyzed Carbonyl-Olefin Metathesis

“…9 The COM reaction has been identified as an attractive replacement to overcome challenges in traditional approaches for the olefination of carbonyl groups, such as pre-functionalization of substrates, reagent synthesis, or the separation of by-products from reaction mixtures. 10 The majority of approaches towards COM reactions are based on Lewis acid catalysts, 11 ranging from transition metal salts such as FeCl3 first reported by Schindler et al 9c,12 and Li et al 9d and subsequently salts of Ga(III) by Schindler 13 and Bour, 9f AuCl3 by Lin et al 14 date, there have been only two reports on efficient Brønsted acid catalyzed COM reactions, with both of them employing elegant but very specially designed systems using fixation of the acid catalyst in a supramolecular capsule by the Tiefenbacher group 21 or within a fixed-bed in continuous flow system by Layva-Pérez and co-workers. 22 Simple generalized methods towards COM reactions that can operate homogeneously in bulk solvent have not been reported thus far.…”

“…9 The COM reaction has been identified as an attractive replacement to overcome challenges in traditional approaches for the olefination of carbonyl groups, such as pre-functionalization of substrates, reagent synthesis, or the separation of by-products from reaction mixtures. 10 The majority of approaches towards COM reactions are based on Lewis acid catalysts, 11 ranging from transition metal salts such as FeCl3 first reported by Schindler et al 9c,12 and Li et al 9d and subsequently salts of Ga(III) by Schindler 13 and Bour, 9f AuCl3 by Lin et al 14 or bimetallic systems such as AlCl3/AgSF6 and AlCl3/AgSF6 by Schindler 15 . Further, more specialized approaches harness the reactivity of hydrazines as organocatalysts as reported by the Lambert group 9a, 16 and a special photocatalytic strategy by the Glorius group.…”

Halogen Bond Catalysis on Carbonyl–OlefinRing‐ClosingMetathesis Reaction: Comparison with Lewis Acid Catalysis

“…[ 5 ] In recent years, considering that the transient coordination of Lewis acid with carbonyl oxygen will promote the cycloaddition reaction and cycloreversion reaction, Lewis acid has become the main catalyst for carbonyl–olefin metathesis. [ 6 ] Compared with metal alkylidene catalysts, the reaction catalyzed by Lewis acid mainly depends on the coordination between the catalyst and the substrate, thus avoiding the formation of metal‐oxygen bonds. [ 7 ]…”

Hydrogen Bonding Networks Enable Brønsted Acid‐Catalyzed Carbonyl‐Olefin Metathesis**

“…and Li et al [12d] . and subsequently salts of Ga III by Schindler [16] and Bour, [12f] AuCl 3 by Lin et al [17] . or bimetallic systems such as AlCl 3 /AgSF 6 and AlCl 3 /AgSF 6 by Schindler [18] .…”