Substituent Effects and Charge Delocalization Mode in Chrysenium, Benzo[<i>c</i>]phenanthrenium, and Benzo[<i>g</i>]chrysenium Cations: A Stable Ion and Electrophilic Substitution Study
作者:Kenneth K. Laali、Takao Okazaki、Subodh Kumar、Sergio E. Galembeck
DOI:10.1021/jo001268b
日期:2001.2.1
disubstituted chrysenes Ch (5- methyl- 3, 2-methoxy- 19, 2-methoxy-11-methyl- 20, 2-methoxy-5-methyl- 21, and 9-methyl-4H-cyclopenta[def]chrysene 22), monosubstituted benzo[c]phenanthrenes BcPh (3-methoxy- 23, 3-hydroxy- 24), and monosubstituted benzo[g]chrysenes BgCh (12-methoxy- 25; 12-hydroxy- 26) were generated in FSO3H/SO2ClF or FSO3H-SbF5 (4:1)/SO2ClF and studied by low-temperature NMR at 500 MHz. The methoxy
Intramolecular gold(III) catalysed Diels–Alder reaction of 1-(2-furyl)-hex-1-en-5-yn-3-ol derivatives: a short and generalised route for the synthesis of hydroxyphenanthrene derivatives
作者:Khokan Samanta、Gandhi K. Kar、Achintya K. Sarkar
DOI:10.1016/j.tetlet.2012.01.018
日期:2012.3
Gold(III) catalysed intramolecular Diels–Alder reaction of various 1-(2-furyl)-hex-1-en-5-yn-3-ol derivatives has been studied to synthesise hydroxyphenanthrenes and other polynuclear aromatic hydroxyl compounds. The required precursors were synthesised by indium mediated propargylation of suitable β-furyl-α,β-unsaturated aldehydes.
Ir-catalyzed borylation of [4]helicene under different reaction conditions was studied for the first time. The results indicate that monoborylation proceeds to give a mixture of 2- and 3-borylated products in good yields (up to 74 % isolated yield). It was possible to shift the selectivity in favor of the 3-borylated product by using sterically demanding ligands. The monoborylated [4]helicenes were further
Exploiting the π-Acceptor Properties of Carbene-Stabilized Phosphorus Centered Trications [L<sub>3</sub>P] <sup>3+</sup>: Applications in Pt(II) Catalysis
Reaction of tris(dimethylaminocyclopropenium) substituted phosphine 1 with K2PtCl4 afforded the bench stable complex 3 which upon treatment with Ag[CB11H6Cl6] turned out to be an excellent catalyst for the transformation of a variety of ortho-biaryl substituted alkynes into polycyclic homo- and heteroarenes of different size, shape, and curvature through a 6-endo-dig cyclization. This constitutes the first example ever reported of using a P-1-centered trication as ligand in catalysis. The strong pi-acceptor character of 1 that derives from its three positive charges substantially increases the intrinsic pi-acidity of Pt in complex 1.PtCl2 and dramatically enhances its ability to activate pi-systems toward nucleophilic attack. As a consequence, a remarkable acceleration of the model transformation is observed when compared with other classical pi-acceptor ligands such as P(OPh)(3) or P(C6F5)(3). Moreover, the employment of 1 as ligand also expands the scope of this reaction to previously inaccessible substitution patterns. Kinetic studies and deuterium labeling experiments as well as density functional theory (DFT) calculations were performed in order to explain these findings.