530-48-3Relevant articles and documents
1,3-Dialkyl- and 1,3-Diaryl-3,4,5,6-tetrahydropyrimidin-2-ylidene Rhodium(I) and Palladium,(II)Complexes: Synthesis, Structure, and Reactivity
Mayr, Monika,Wurst, Klaus,Ongania, Karl-Hans,Buchmeiser, Michael R.
, p. 1256 - 1266 (2004)
The synthesis of novel 1,3-diaryl- and 1, 3-dialkylpyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and their rhodium(I) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (7), bromo-(cod) (1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (8) (cod = η4-1,5-cyclooctadiene, mesityl = 2,4,6-trimethylphenyl), chloro(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (9), and chloro-(cod) [1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (10) were prepared by reaction of [{Rh(cod)Cl}2] with lithium tert-butoxide followed by addition of 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium bromide (3), 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (4), 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium bromide (6), and 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P21/n, and 8 in the monoclinic space group P21. Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)-rhodium (11), and dicarbonyl-chloro[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene] rhodium (12). The wavenumbers v(CO I)/v(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/ 1976 and 2063/1982 cm-1, respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(I) bis-NHC complexes [Ag(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)2] AgBr2 (13) and [Ag{1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene] 2]AgBr2 (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene) 22+ (Ag2Br2-Cl4 4-)1/2 (15) and Pd[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)2]-Cl 2 (16). Complex 15 crystallizes in the monoclinic space group P2 1/c, and 16 in the monoclinic space group C2/c. The catalytic activity of 15 and 16 in Heck-type reactions was studied in detail. Both compounds are highly active in the coupling of aliphatic and aromatic vinyl compounds with aryl bromides and chlorides with turnover numbers (TONs) up to 2 000 000. Stabilities of 15 and 16 under Heck-couplings conditions were correlated with their molecular structure. Finally, selected kinetic data for these couplings are presented.
A Boratafulvene
Heitkemper, Tobias,Na?, Leonard,Sindlinger, Christian P.
, p. 20055 - 20060 (2021)
Structurally authenticated free B-alkyl boroles are presented and electronic implications of alkyl substitution were assessed. Deprotonation of a boron-bound exocyclic methyl group in a B-methyl borole yields the first 5-boratafulvene anion—an isomer to boratabenzene. Boratafulvene was structurally characterized and its electronic structure probed by DFT calculations. The pKa value of the exocyclic B?CH3 in a set of boroles was computationally approximated and confirmed a pronounced acidic character caused by the boron atom embedded in an anti-aromatic moiety. The non-aromatic boratafulvene reacts as a C-centered nucleophile with the mild electrophile Me3SnCl to give a stannylmethyl borole, regenerating the anti-aromaticity. As nucleophilic synthons for boroles, boratafulvenes thus open an entirely new avenue for synthetic strategies toward this highly reactive class of heterocycles. Boratafulvene reacts as a methylene transfer reagent in a bora-Wittig-type reaction generating a borole oxide.
Substituent effects on sulfonate ester based olefinations
Hawkins,Lewis,Raw
, p. 981 - 984 (1990)
The anions of sulfonate esters derived from acidic alcohols olefinate carbonyl compounds. The dependence of the yield and stereochemistry of olefination on the sulfonate ester's alkoxy substituent are consistent with a mechanism were apicophilic alkoxy groups promote olefination via 10-S-5 intermediate 3.
INTERCONVERSIONS OF TITANOCENE-METHYLENE COMPLEXES
Heisteeg, B. J. van de,Schat, G.,Akkerman, O. S.,Bickelhaupt, F.
, p. 6493 - 6496 (1987)
The Tebbe-type reagent Cp2Ti(X)CH2MgX (X=Br, Cl) (2) in diethyl ether/benzene gave, on evaporation of the solvent and solution in toluene, Cp2(Br)TiCH2MgCH2Ti(Br)Cp2 (3).Both compounds differ dramatically in their spectral properties and reactivities.Compound 3 reacts with ethers to give Cp2TiCH2Ti(Cp2)CH2 (4), with PMe3 to give Cp2(MeP3)Ti=CH2 (5) and with benzophenone to give 1,1-diphenylethene.Analogous derivatives were obtained from Cp'2TiCl2 (Cp'=MeC5H4).
Dynamic Isotope Dilution as a General Method for Ascertaining Partition of Photochemical Pathways Potentially Utilizing Nondiscernible Intermediates: Application to a New Reaction
Zimmerman, Howard E.,Carpenter, Clint W.,Weber, Andrew M.
, p. 1073 - 1075 (1985)
-
Convenient Access to Gallium(I) Cations through Hydrogen Elimination from Cationic Gallium(III) Hydrides
Peverati, Roberto,Powell, Douglas R.,Wehmschulte, Rudolf J.
, p. 12441 - 12445 (2019)
Although gallium hydrides XnGaH3-n (X = monoanionic substituent) are usually stable compounds, cationic arene-solvated species [H2Ga(arene)2]+ spontaneously eliminate dihydrogen at room temperature to afford the arene-solvated gallium(I) compounds [Ga(PhF)2][CHB11Cl11] (1) and [Ga(Ph3CH)][B(C6F5)4] (3). A key requirement appears to be the presence of a weakly coordinating anion. Use of the more basic triflimide anion, [NTf2]-, reverses the stability, i.e., the gallium(III) hydride H2GaNTf2 (4) is more stable than the gallium(I) compound GaNTf2 (5). The experimental results are supported by DFT calculations. Compounds 1 and 3 can be used as catalysts for the oligomerization of 2,4,4-trimethyl-1-pentene and the hydrosilylation of benzophenone and 1-hexene.
Siletanylmethyllithium: An ambiphilic organosilane
Kozytska, Mariya V.,Dudley, Gregory B.
, p. 3047 - 3049 (2005)
The adjacent centres of electrophilicity and nucleophilicity lead to interesting chemical reactivity in the title reagent. The Royal Society of Chemistry 2005.
Syntheses and characterization of palladium(II) complexes with tridentate N-heterocyclic carbene ligands containing aryloxy groups and their application to Heck reaction
Yagyu, Takeyoshi,Oya, Shoko,Maeda, Masunobu,Jitsukawa, Koichiro
, p. 154 - 155 (2006)
Two palladium(II) complexes with tridentate N-heterocyclic carbene ligands containing aryloxy groups were prepared and characterized by X-ray crystallographic method. They showed good performance for Heck reaction. Copyright
Direct Allylic C(sp3)?H and Vinylic C(sp2)?H Thiolation with Hydrogen Evolution by Quantum Dots and Visible Light
Huang, Cheng,Ci, Rui-Nan,Qiao, Jia,Wang, Xu-Zhe,Feng, Ke,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
supporting information, p. 11779 - 11783 (2021/04/21)
Direct allylic C?H thiolation is straightforward for allylic C(sp3)?S bond formation. However, strong interactions between thiol and transition metal catalysts lead to deactivation of the catalytic cycle or oxidation of sulfur atom under oxidative condition. Thus, direct allylic C(sp3)?H thiolation has proved difficult. Represented herein is an exceptional for direct, efficient, atom- and step-economic thiolation of allylic C(sp3)?H and thiol S?H under visible light irradiation. Radical trapping experiments and electron paramagnetic resonance (EPR) spectroscopy identified the allylic radical and thiyl radical generated on the surface of photocatalyst quantum dots (QDs). The C?S bond formation does not require external oxidants and radical initiators, and hydrogen (H2) is produced as byproduct. When vinylic C(sp2)?H was used instead of allylic C(sp3)?H bond, the radical-radical cross-coupling of C(sp2)?H and S?H was achieved with liberation of H2. Such a unique transformation opens up a door toward direct C?H and S?H coupling for valuable organosulfur chemistry.
Electrochemical fluorosulfonylation of styrenes
Jiang, Yi-Min,Wu, Shao-Fen,Yan, Hong,Ye, Ke-Yin,Yu, Yi,Yuan, Yaofeng
supporting information, p. 11481 - 11484 (2021/11/16)
An environmentally friendly and efficient electrochemical fluorosulfonylation of styrenes has been developed. With the use of sulfonylhydrazides and triethylamine trihydrofluoride, a diverse array of β-fluorosulfones could be readily obtained. This reaction features mild conditions and a broad substrate scope, which could also be conveniently extended to a gram-scale preparation.
