- Polycationic ligands in gold catalysis: Synthesis and applications of extremely π-acidic catalysts
-
Very often ligands are anionic or neutral species. Cationic ones are rare, and, when used, the positively charged groups are normally appended to the periphery of the ligand. Here, we describe a dicationic phosphine with no spacer between the phosphorus atom and the two positively charged groups. This structural feature makes its donor ability poorer than that of phosphites and only comparable to extremely toxic or pyrophoric compounds such as PF 3 or P(CF3)3. By exploiting these properties, a new Au catalyst has been developed displaying a dramatically enhanced capacity to activate π-systems. This has been used to synthesize very sterically hindered and naturally occurring 4,5-disubstituted phenanthrenes. The present approach is expected to be applicable to the development and improvement of many other transition metal catalyzed transformations that benefit from extremely strong π-acceptor ligands. The mechanism of selected catalytic transformations has been explored by density functional calculations.
- Carreras, Javier,Gopakumar, Gopinadhanpillai,Gu, Liangu,Gimeno, Ana,Linowski, Pawel,Petu?kova, Jekaterina,Thiel, Walter,Alcarazo, Manuel
-
p. 18815 - 18823
(2014/01/06)
-
- Cyclopentindene (Benzopentalene) and Pentalene: Pyrolytic Formation from 3-Phenyl- and 3-Vinyl-phthalic Anhydrides
-
Pyrolysis of 3-phenylphthalic anhydride at 900 deg/0.02 mm gives cyclopentindene, characterized by 1H n.m.r. at -70 deg and by formation of a cyclopentadiene adduct and of a dimer at room temperature.Pyrolysis of 3,4-, 3,5- and 3,6-diphenylphthalic anhydrides also gives much cyclopentindene by loss of the additional phenyl group. 3,4-diphenylphthalic anhydride forms triphenylene as the major product.The pyrolysate from 3-vinylphthalic anhydride contains the known dimer of pentalene, and phenylacetylene.Pyrolyses of 3-(1-naphthyl)phthalic anhydride and of 4-phenylphenanthrene-2,3-dicarboxylic anhydride are described.
- Brown, Roger F. C.,Choi, Neil,Eastwood, Frank W.
-
p. 185 - 198
(2007/10/02)
-
- The mechanism of the photooxidation of 1-(9-phenanthryl)-4-phenyl-1-buten-3-yne
-
Irradiation of 1-(9-phenanthryl)-4-phenylbutenyne (1) in aprotic solvents containing oxygen gives two products, namely a photocyclization product, 1-phenyltriphenylene 3, as is usually formed from diarylbutenynes, and photooxidation product (2), derived f
- Arendonk, R. J. F. M. van,Laarhoven, W. H.
-
p. 263 - 267
(2007/10/02)
-