Ionization of gold (γ-methoxy)vinyl complexes generates reactive gold vinyl carbene complexes

Abstract

Highly reactive cationic gold vinyl carbene/allylic cation complexes are generated in solution via γ-ionization of gold vinyl complexes.

Gold Sulfonium Benzylide Complexes Undergo Efficient Benzylidene Transfer to Alkenes

“…Largely absent from the discussion of the mechanisms of gold to alkene carbene transfer are the potential insights gained from analysis of carbene transfer from well‐defined carbene complexes in the condensed phase . Recent efforts in this area have led to the identification of a small number of well‐defined gold carbene complexes that undergo carbene transfer to alkenes ( A – C ) . However, extracting detailed mechanistic information relevant to catalysis from these stoichiometric carbene transfer processes is complicated by the (1) excessive stabilization of the carbene complex, (2) in situ generation of the carbene complex with strong Lewis acids under cryogenic conditions, and/or (3) the extreme facility of carbene transfer …”

“…[4,[14][15][16][17][18][19] Largelya bsentf rom the discussion of the mechanisms of gold to alkene carbenet ransfer are the potentiali nsights gained from analysiso fc arbene transferf rom well-defined carbene complexes in the condensed phase. [20][21][22] However,e xtracting detailed mechanistic information relevant to catalysis from these stoichiometric carbene transfer processes is complicated by the (1) excessive stabilization of the carbene complex, (2) in situ generation of the carbene complex with strong Lewis acids underc ryogenic conditions, and/or( 3) the extreme facility of carbene transfer. [20][21][22] However,e xtracting detailed mechanistic information relevant to catalysis from these stoichiometric carbene transfer processes is complicated by the (1) excessive stabilization of the carbene complex, (2) in situ generation of the carbene complex with strong Lewis acids underc ryogenic conditions, and/or( 3) the extreme facility of carbene transfer.…”

“…[2,3] Recent efforts in this area have led to the identification of as mall number of well-defined gold carbene complexes that undergo carbene transfer to alkenes (A-C). [20][21][22] As an alternative to free gold carbene complexes, we sought to identify gold carbenoid complexest hat would spontaneously and reversibly generate reactive gold carbene complexes in solution under mild conditions, [23] thereby allowing kinetic and mechanistic analysiso fc arbene transfer processes from otherwise inaccessible gold carbene complexes.A lthoughasmall number of gold(I)c arbenoid complexes that undergo carbene transfer to alkenesh aveb een identified (e.g., D-F; Figure1), [17,19,24] only imidazolium sulfonyl complex F does so in solution withoutL ewis acid activation. [20][21][22] As an alternative to free gold carbene complexes, we sought to identify gold carbenoid complexest hat would spontaneously and reversibly generate reactive gold carbene complexes in solution under mild conditions, [23] thereby allowing kinetic and mechanistic analysiso fc arbene transfer processes from otherwise inaccessible gold carbene complexes.A lthoughasmall number of gold(I)c arbenoid complexes that undergo carbene transfer to alkenesh aveb een identified (e.g., D-F; Figure1), [17,19,24] only imidazolium sulfonyl complex F does so in solution withoutL ewis acid activation.…”

“…[20][21][22] However,e xtracting detailed mechanistic information relevant to catalysis from these stoichiometric carbene transfer processes is complicated by the (1) excessive stabilization of the carbene complex, (2) in situ generation of the carbene complex with strong Lewis acids underc ryogenic conditions, and/or( 3) the extreme facility of carbene transfer. [20][21][22] As an alternative to free gold carbene complexes, we sought to identify gold carbenoid complexest hat would spontaneously and reversibly generate reactive gold carbene complexes in solution under mild conditions, [23] thereby allowing kinetic and mechanistic analysiso fc arbene transfer processes from otherwise inaccessible gold carbene complexes.A lthoughasmall number of gold(I)c arbenoid complexes that undergo carbene transfer to alkenesh aveb een identified (e.g., D-F; Figure1), [17,19,24] only imidazolium sulfonyl complex F does so in solution withoutL ewis acid activation. [18,25,26] However carbene transferf rom F requiresf orcingc onditions and as tabilizing C1 anisyl group for spontaneous activation and undergoes irreversible carbene formation, all of whichw ould complicate kinetic andm echanistic analysiso fc arbene transfer.…”

Formation of Cyclopropanes via Activation of (γ-Methoxy)alkyl Gold(I) Complexes with Lewis Acids

“…2,3 There has likewise been a considerable effort directed toward understanding the structure and behavior of cationic gold carbene complexes 4 and toward the synthesis of well-defined gold carbene complexes that undergo carbene transfer to alkenes. 5,6 Despite the prevalence of gold to alkene carbene transfer, the intimate mechanisms of these transformations remain unclear. Both computation 7−10 and experiment 7 point to mechanisms for gold to alkene carbene transfer initiated by nucleophilic attack of the alkene on the electrophilic carbene carbon, but within this framework of electrophilic cyclopropanation, 11 a number of alkene-and carbene-dependent mechanisms have been postulated.…”