28294-36-2Relevant academic research and scientific papers
Stable group 8 metal porphyrin mono- And bis(dialkylcarbene) complexes: Synthesis, characterization, and catalytic activity
Che, Chi-Ming,Huang, Jie-Sheng,Low, Kam-Hung,Wan, Qingyun,Wang, Hai-Xu,Zhang, Jun-Long,Zhou, Cong-Ying
, p. 2243 - 2259 (2020/03/11)
Alkyl-substituted carbene (CHR or CR2, R = alkyl) complexes have been extensively studied for alkylcarbene (CHR) ligands coordinated with high-valent early transition metal ions (a.k.a. Schrock carbenes or alkylidenes), yet dialkylcarbene (CR2) complexes remain less developed with bis(dialkylcarbene) species being little (if at all) explored. Herein, several group 8 metal porphyrin dialkylcarbene complexes, including Fe- and Ru-mono(dialkylcarbene) complexes [M(Por)(Ad)] (1a,b, M = Fe, Por = porphyrinato dianion, Ad = 2-adamantylidene; 2a,b, M = Ru) and Os-bis(dialkylcarbene) complexes [Os(Por)(Ad)2] (3a-c), are synthesized and crystallographically characterized. Detailed investigations into their electronic structures reveal that these complexes are formally low-valent M(ii)-carbene in nature. These complexes display remarkable thermal stability and chemical inertness, which are rationalized by a synergistic effect of strong metal-carbene covalency, hyperconjugation, and a rigid diamondoid carbene skeleton. Various spectroscopic techniques and DFT calculations suggest that the dialkylcarbene Ad ligand is unique compared to other common carbene ligands as it acts as both a potent σ-donor and π-acceptor; its unique electronic and structural features, together with the steric effect of the porphyrin macrocycle, make its Fe porphyrin complex 1a an active and robust catalyst for intermolecular diarylcarbene transfer reactions including cyclopropanation (up to 90% yield) and X-H (X = S, N, O, C) insertion (up to 99% yield) reactions.
Hypervalent-iodine(iii) oxidation of hydrazones to diazo compounds and one-pot nickel(ii)-catalyzed cyclopropanation
Liu, Haixuan,Wei, Yunyang,Cai, Chun
, p. 674 - 678 (2016/01/12)
A one-pot process for the catalytic cyclopropanation of various alkenes with unsubstituted hydrazones is described. Iodosobenzene (Ph = O) was found to be a competent oxidant of hydrazones to diazo compounds. Ni(OH)2 was chosen as an effective and cheap metal catalyst. The cyclopropane products can be generated efficiently (5 min-4 h) in moderate to good yields (42-91%) under mild (80°C) and neat conditions.
DIKETIMINATO CU(I) AND CO(I) CARBENE CATALYSTS, AND CYCLOPROPANATION METHODS USING THEM
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Page/Page column 47-48, (2008/06/13)
The present invention described herein employs employs Cu(I) complexes of an electron-rich, bidentate N,N-donor ligand (P-diketiminates) that react with both heteroatomcontaining a-substituted diazomethanes and ary1diazomethanes to yield a unique metal-carbene complex stabilized by two metal fragments that selectively reacts with alkenes. These examples are the first of isolable Cu-carbene complexes that react with alkenes to give cyclopropanes. Furthermore, electron-rich, bidentate N,N-donor ligands can be designed to impart stereo- and enantio-selectivity in the cyclopropanation of alkenes with diazoalkanes.
Discrete bridging and terminal copper carbenes in copper-catalyzed cyclopropanation
Dai, Xuliang,Warren, Timothy H.
, p. 10085 - 10094 (2007/10/03)
The Cu(I)/ β-diketiminate [Me2NN]Cu(η2- ethylene) (2) catalyzes the cyclopropanation of styrene with N 2CPh2 to give 1,1,2-triphenylcyclopropane in 67% yield. Addition of N2CPh2 to 2 equiv of 2 allows for the isolation of the dicopper carbene {[Me2NN]Cu}2(μ- CPh2) (3) in which the diphenylcarbene moiety is symmetrically bound between two [Me2NN]Cu fragments (Cu-C = 1,922(4) and 1.930(4) A) with a Cu-Cu separation of 2.4635(7) A. In toluene-d8 solution, 3 reversibly dissociates a [Me2NN]Cu fragment to give [Me2NN]Cu(toluene) and the terminal carbene [Me2NN]Cu= CPh2, Dicopper carbene 3 reacts with 3 equiv of styrene to give 1,1,2-triphenylcyclopropane and 2 equiv of [Me2NN] Cu(η2-styrene) within minutes, DFT studies with simplified ligands indicate a stronger Cu-C π-back-bonding interaction from two Cu(I) centers to the carbene acceptor orbital in a dicopper carbene than that present in a monocopper carbene. Nonetheless, the terminal carbene [Me 3NN]Cu=CPh2 (8) that possesses a p-methyl group on each β-diketiminato N-aryl ring may be isolated and exhibits a shortened Cu-C distance of 1,834(3) A, The stoichiometric cyclopropanation of styrene by 8 in 1,4-dioxane is first-order in both copper carbene 8 and styrene with activation parameters ΔH? = 10,4(3) kcal/mol and ΔS? = -32,3(9) cal/mol·K. In 1,4-dioxane, 8 decomposes to Ph 2C=CPh2 via first-order kinetics with activation parameters ΔH? = 21(1) kcal/mol and ΔS? = -8(3) cal/mol·K. Arene solutions of thermally sensitive terminal carbene 8 decompose to [Me3NN]-Cu(arene), which reacts with 8 still present in solution to give the more thermally stable {[Me3NN]Cu} 2-(μ-CPh2).
Effects of Aryl Substituents on Electron-Transfer-Mediated Photochemical Addition of Alcohol to 1,1,2-Triarylcyclopropanes
Tomioka, Hideo,Inoue, Osamu
, p. 1404 - 1406 (2007/10/02)
Direct irradiation of 1,1,2-triarylcyclopropanes in alcohol resulted in the formation of all possible products arising from trimethylene biradicals, while DCB-sensitised irradiation gave a novel "anti-Markownikoff" addition product of alcohol almost exclusively.In order to get insight into the nature and fate of intermediates in the reactions, the effects of nucleophiles and aryl substituents are examined.
THE PHILICITY OF A TRIPLET CARBENE: ADDITIONS OF DIPHENYLCARBENE TO STYRENE SUBSTRATES
Tomioka, Hideo,Ohno, Kumiko,Izawa, Yasuji,Moss, Robert A.,Munjal, Ramesh C.
, p. 5415 - 5418 (2007/10/02)
Triplet diphenylcarbene adds to ring-substituted styrenes as an ambiphile, reacting more rapidly with electron-rich or electron-poor styrenes than with styrene itself.
