Highly Efficient Route to Fused Polycyclic Aromatics via Palladium-Catalyzed Aryne Annulation by Aryl Halides
作者:Zhijian Liu、Richard C. Larock
DOI:10.1021/jo0619534
日期:2007.1.1
Polycyclic aromatic and heteroaromatic hydrocarbons have been synthesized in high yield by two different processes involving the Pd-catalyzed annulation of arynes. The first process involves a Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides. The second process utilizes a Pd-catalyzed double annulation of arynes by simple aryl halides. Both processes appear to involve
Dioxomolybdenum(VI)-Catalyzed Reductive Cyclization of Nitroaromatics. Synthesis of Carbazoles and Indoles
作者:Roberto Sanz、Jaime Escribano、María R. Pedrosa、Rafael Aguado、Francisco J. Arnáiz
DOI:10.1002/adsc.200600384
日期:2007.3.5
Reductive cyclization of nitrobiphenyls and nitrostyrenes to carbazoles and indoles, respectively, is carried out by triphenylphosphine under mild conditions catalyzed by a dichlorodioxomolybdenum(VI) complex. A one-pot procedure for the synthesis of regioselectively functionalized indoles has been developed from commercially available o-nitrobenzaldehydes and phosphoranes.
Various nitro-substituted aryl and heteroaryl iodides undergo an iodine-magnesium exchange reaction when treated with PhMgCl leading to nitro-containing magnesium organometallics. These Grignard reagents display an excellent stability at temperatures below -40 degrees C and do not undergo electron-transfer reactions. They react as expected with various electrophiles.
Aryl to Aryl Palladium Migration in the Heck and Suzuki Coupling of <i>o</i>-Halobiaryls
作者:Marino A. Campo、Haiming Zhang、Tuanli Yao、Abdellatif Ibdah、Ryan D. McCulla、Qinhua Huang、Jian Zhao、William S. Jenks、Richard C. Larock
DOI:10.1021/ja069238z
日期:2007.5.1
A novel 1,4-palladium migration between the o- and o'-positions of biaryls has been observed in organopalladium intermediates derived from o-halobiaryls. The organopalladium intermediates generated by this migration have been trapped either by a Heck reaction employing ethyl acrylate or by Suzuki cross-coupling using arylboronic acids. This palladium migration can be activated or deactivated by choosing the appropriate reaction conditions. Chemical and computational evidence supports the presence of an equilibrium that correlates with the C-H acidity of the available arene positions.