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101.
Chunguang HanYoshi Yamano Fumitoshi KakiuchiKazuhiko Nakamura Daisuke Uemura 《Tetrahedron》2011,67(49):9622-9626
An oxidative cleavage of allyl vic-diols to aldehydes catalyzed by a Grubbs carbene complex using a co-oxidant has been established for the first time, with good yields. The utility of this selective cleavage reaction was demonstrated through the use of two huge marine molecules, symbiodinolide and N-p-BrBz palytoxin. 相似文献
102.
Alcohol‐Induced C−N Bond Cleavage of Cyclometalated N‐Heterocyclic Carbene Ligands with a Methylene‐Linked Pendant Imidazolium Ring
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Dr. Wei Zhong Dr. Zhaofu Fei Dr. Rosario Scopelliti Prof. Dr. Paul J. Dyson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12138-12144
Reaction of the pentamethylcyclopentadienyl rhodium iodide dimer [Cp*RhI2]2 with 1,1′‐diphenyl‐3,3′‐methylenediimidazolium diiodide in non‐alcohol solvents, in the presence of base, led to the formation of bis‐carbene complex [Cp*Rh(bis‐NHC)I]I (bis‐NHC=1,1′‐diphenyl‐4,4′‐methylenediimidazoline‐5,5′‐diylidene). In contrast, when employing alcohols as the solvent in the same reaction, cleavage of a methylene C?N bond is observed, affording ether‐functionalized (cyclometalated) carbene ligands coordinated to the metal center and the concomitant formation of complexes with a coordinated imidazole ligand. Studies employing other 1,1′‐diimidazolium salts indicate that the cyclometalation step is a prerequisite for the activation/scission of the C?N bond and, based on additional experimental data, a SN2 mechanism for the reaction is tentatively proposed. 相似文献
103.
104.
Asymmetric,Three‐Component,One‐Pot Synthesis of Spiropyrazolones and 2,5‐Chromenediones from Aldol Condensation/NHC‐Catalyzed Annulation Reactions
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Dr. Lei Wang Sun Li Dr. Pankaj Chauhan Dr. Daniel Hack Arne R. Philipps Dr. Rakesh Puttreddy Prof. Dr. Kari Rissanen Prof. Dr. Gerhard Raabe Prof. Dr. Dieter Enders 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5123-5127
A novel one‐pot, three‐component diastereo‐ and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β‐unsaturated pyrazolones, which react with a second equivalent of enal through an N‐heterocyclic carbene (NHC)‐catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1,3‐diketones, 2,5‐chromenediones are available through [2+4] annulation. 相似文献
105.
Investigation of N‐Heterocyclic Carbene‐Supported Group 12 Triflates as Pre‐catalysts for Hydrosilylation/Borylation
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Matthew M. D. Roy Dr. Michael J. Ferguson Dr. Robert McDonald Prof. Dr. Eric Rivard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18236-18246
N‐Heterocyclic carbene (NHC) complexes of Cd and Hg triflates (OTf) were prepared and their attempted conversion into rare cadmium and mercury hydrides was explored. In contrast to zinc, which forms stable [ZnH]+ complexes with NHCs, the heavier Cd and Hg congeners could not be formed; the increased instability of Cd‐H and Hg‐H units was rationalized with the aid of computations. It was also discovered that the dimeric adduct [IPr?Cd(μ‐OTf)2]2 (IPr=[(HCNDipp)2C:]; Dipp=2,6‐iPr2C6H3) is an active precatalyst for the hydrosilylation and hydroborylation of hindered aldehydes and ketones. The related zinc congener was inactive as a catalyst highlighting a distinct advantage of using heavy Group 12 metals to promote catalytic hydrosilylation/borylation. 相似文献
106.
Wojciech Czardybon Wojciech Sokol John Warkentin Nick Henry Werstiuk 《Journal of Physical Organic Chemistry》2008,21(1):41-46
Synthesis of a bicyclic 2,2‐dioxa oxadiazoline (6,7‐diaza‐1‐methoxy‐5‐methyl‐2,8‐dioxabicyclo[3.2.1]oct‐6‐ene) is reported. Its thermolysis at 27°C is about 200 times as fast as the thermolysis of a monocyclic oxadiazoline model system. Presumably, a cyclic dioxa carbonyl ylide is formed initially and the ylide then undergoes a bond scission to afford either a dioxacarbene or a dialkylcarbene or it cyclizes to an oxirane. A small fraction of a dialkylcarbene was trapped as the product of addition to dimethyl acetylenedicarboxylate (DMAD). Computations of the barriers to the loss of N2 from the oxadiazolines and to the formation of the carbenes from the carbonyl ylide resulting from thermolysis of the bicyclic oxadiazoline are compared to corresponding barriers for a similar monocyclic oxadiazoline. The rate acceleration is accounted for in terms of geometric factors. The complex products from the decomposition of the bicyclic oxadiazoline were not studied. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
107.
108.
Miqueu K Despagnet-Ayoub E Dyer PW Bourissou D Bertrand G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(23):5858-5864
Density functional calculations are reported for complexes of general formula [(carbene)RhClL(2)] featuring model phosphino- and aminocarbenes. Both the cis and trans isomers of the rhodium(I) eta(1)-complexes (1-9) were investigated, and the influence of the rhodium co-ligands (L=ethylene, phosphine, or carbon monoxide) was evaluated. In the case of phosphinocarbenes and carbon monoxide as a ligand, a somewhat unusual coordination mode was observed, in which a significant intramolecular Cl-->C(carbene) interaction is present. The propensity of phosphino- and aminocarbenes to behave as four electron donors was also investigated both structurally and energetically on the related eta(2)-complexes 10-18. These results as a whole emphasize the structural versatility of phosphino- compared with aminocarbene complexes. 相似文献
109.
110.
Lingling Peng 《Journal of organometallic chemistry》2011,696(1):118-122
[RuCl2(p-cymene)]2 efficiently catalyzes the rearrangement of 2-aryl-2-(phenylthio)penta-3,4-dienyl 2,2,2-trichloroacetimidate to afford (Z)-2,2,2-trichloro-N-(4-aryl-1-(phenylthio)penta-2,4-dien-2-yl)acetamide. Ru carbene is assumed as the reactive intermediate in this rearrangement. 相似文献