- Negishi cross-coupling reaction catalyzed by an aliphatic, phosphine based pincer complex of palladium. biaryl formation via cationic pincer-type Pd IV intermediates
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The aliphatic, phosphine-based pincer complex [(C10H 13-1,3-(CH2P(Cy2)2)Pd(Cl)] (1) is a highly active Negishi catalyst, enable to quantitatively couple various electronically activated, non-activated, deactivated, sterically hindered and functionalized aryl bromides with various diarylzinc reagents within short reaction times and low catalyst loadings. Experimental observations strongly indicate that a molecular mechanism is operative with initial chloride dissociation of 1 and formation of the cationic T-shaped 14e- complex [(C10H13-1,3-(CH2P(C6H 11)2)2)Pd]+ (B), which undergoes oxidative addition of an aryl bromide (Ar′Br) to yield the cationic, penta-coordinated aryl bromide pincer complexes of type [(C10H 13-1,3-(CH2P(Cy2)2)Pd(Br) (aryl′)]+ (C) with the metal center in the oxidation state of +IV and the aryl unit in cis position relative to the aliphatic pincer core. Subsequent transmetalation with Zn(aryl)2 result in the cationic diaryl pincer complexes of type [(C10H13-1,3-(CH 2P(Cy2)2)Pd(aryl)(aryl′)]+ (D), which reductively eliminate the coupling products, thereby regenerating the catalyst. The neutral square planar aryl pincer complex - a possible key intermediate in the catalytic cycle - was found to be reversibly formed in the reaction mixture but is not involved in the catalytic mechanism. Similarly, palladium nanoparticles as the catalytically active form of 1 could have been excluded. The Royal Society of Chemistry 2011.
- Gerber, Roman,Blacque, Olivier,Frech, Christian M.
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experimental part
p. 8996 - 9003
(2011/10/31)
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- Anthracenylporphyrins
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We report the synthesis and characterization of meso-anthracenylporphyrins with zinc and nickel metal centers. A variety of novel aryl and alkyl meso-substituted anthracenylporphyrins were synthesized via step-wise Suzuki cross-coupling reactions using an
- Davis, Mia,Senge, Mathias O.,Locos, Oliver B.
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experimental part
p. 1472 - 1484
(2011/02/28)
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- Picosecond Laser Spectroscopy of Intramolecular Heteroexcimer Systems. Time-resolved Fluorescence Studies of p-(CH3)2NC6H4-(CH2)n-(9-Anthryl), p-(CH3)2NC6H4-(CH2)n-(1-Pyrenyl) Systems and 9,9'-Bianthryl
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In order to elucidate the details of elementary processes of photochemical charge transfer and heteroexcimer formation processes, and also in order to compare the obtained results with those of transient absorption spectral measurements, we have examined
- Migita, Masahito,Okada, Tadashi,Mataga, Noboru,Sakata, Yoshiteru,Misumi, Soichi,et al.
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p. 3304 - 3311
(2007/10/02)
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- Photochemical Reactions of Aromatic Compounds. XXXVI. The Photoreactions of Anthracene with Some Selected Tertiary Aromatic Amines in Polar Media
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The photoreaction of anthracene witn N,N-dimethylaniline in acetonitrile gave 9-(p-dimethylaminophenyl)-9,10-dihydroanthracene in a good yield, along with 9,10-dihydroanthracene and 9,9',10,10'-tetrahydro-9,9'-bianthryl.This photoreaction was found to depend on the polarity of the solvent as well as on its protic or aprotic nature.With N,N-dimethyl-m-toluidine, a similar 1 : 1 adduct was obtained, while the reduced anthracenes were mainly formed in the photoreactions with N,N-dimethyl-o- and p-toluidines.The mechanisms were discussed in terms of the dissociation into the ion radical as well as their reactivities.
- Yasuda, Masahide,Pac, Chyongjin,Sakurai, Hiroshi
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p. 2352 - 2355
(2007/10/02)
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