17103-83-2Relevant articles and documents
Structure and Reactivity of Half-Sandwich Rh(+3) and Ir(+3) Carbene Complexes. Catalytic Metathesis of Azobenzene Derivatives
Tindall, Daniel J.,Werlé, Christophe,Goddard, Richard,Philipps, Petra,Farès, Christophe,Fürstner, Alois
, p. 1884 - 1893 (2018)
Traditional rhodium carbene chemistry relies on the controlled decomposition of diazo derivatives with [Rh2(OAc)4] or related dinuclear Rh(+2) complexes, whereas the use of other rhodium sources is much less developed. It is now shown that half-sandwich carbene species derived from [Cp?MX2]2 (M = Rh, Ir; X = Cl, Br, I, Cp? = pentamethylcyclopentadienyl) also exhibit favorable application profiles. Interestingly, the anionic ligand X proved to be a critical determinant of reactivity in the case of cyclopropanation, epoxide formation and the previously unknown catalytic metathesis of azobenzene derivatives, whereas the nature of X does not play any significant role in 'OH insertion reactions. This perplexing disparity can be explained on the basis of spectral and crystallographic data of a representative set of carbene complexes of this type, which could be isolated despite their pronounced electrophilicity. Specifically, the donor/acceptor carbene 10a derived from ArC( - N2)COOMe and [Cp?RhCl2]2 undergoes spontaneous 1,2-migratory insertion of the emerging carbene unit into the Rh-Cl bond with formation of the C-metalated rhodium enolate 11. In contrast, the analogous complexes 10b,c derived from [Cp?RhX2]2 (X = Br, I) as well as the iridium species 13 and 14 derived from [Cp?IrCl2]2 are sufficiently stable and allow true carbene reactivity to be harnessed. These complexes are competent intermediates for the catalytic metathesis of azobenzene derivatives, which provides access to α-imino esters that would be difficult to make otherwise. Rather than involving metal nitrenes, the reaction proceeds via aza-ylides that evolve into diaziridines; a metastable compound of this type has been fully characterized.
Epoxides and aziridines from diazoacetates via ylide intermediates.
Doyle,Hu,Timmons
, p. 933 - 935 (2001)
An effective methodology is reported for stereospecific epoxidation and aziridination via carbonyl ylide intermediates using rhodium(II) acetate catalyzed reactions of phenyl- and styryldiazoacetates with aldehydes, ketones, or imines.
Well-Defined, Versatile and Recyclable Half-Sandwich Nickelacarborane Catalyst for Selective Carbene-Transfer Reactions
Wang, Linghua,Perveen, Saima,Ouyang, Yizhao,Zhang, Shuai,Jiao, Jiao,He, Gang,Nie, Yong,Li, Pengfei
supporting information, p. 5754 - 5760 (2021/03/08)
Catalytic carbene-transfer reactions constitute a class of highly useful transformations in organic synthesis. Although catalysts based on a range of transition-metals have been reported, the readily accessible nickel(II)-based complexes have been rarely used. Herein, an air-stable nickel(II)-carborane complex is reported as a well-defined, versatile and recyclable catalyst for selective carbene transfer reactions with low catalyst loading under mild conditions. This catalyst is effective for several types of reactions including diastereoselective cyclopropanation, epoxidation, selective X?H insertions (X = C, N, O, S, Si), particularly for the unprotected substrates. This represents a rare example of carborane ligands in base metal catalysis.
Bis(imino)pyridine iron complexes for catalytic carbene transfer reactions
Wang, Ban,Howard, Isaac G.,Pope, Jackson W.,Conte, Eric D.,Deng, Yongming
, p. 7958 - 7963 (2019/09/06)
The bis(imino)pyridine iron complex, for the first time, is developed as an effective metal carbene catalyst for carbene transfer reactions of donor-acceptor diazo compounds. Its broad catalytic capability is demonstrated by a range of metal carbene reactions, from cyclopropanation, cyclopropenation, epoxidation, and Doyle-Kirmse reaction to O-H insertion, N-H insertion, and C-H insertion reactions. The asymmetric cyclopropanation of styrene and methyl phenyldiazoacetate was successfully achieved by the new chiral bis(imino)pyridine iron catalyst, which delivers a new gateway for the development of chiral iron catalysis for metal carbene reactions.
