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.
[GRAPHICS]PtO2- and H2PtCl6-catalyzed hydrosilylation of internal aryl alkynes having a para or an ortho substituent with triethylsilane are discussed and compared. The regioselectivity of the H-Si bond addition was found to be controlled by the ortho substituent rather than the nature of the platinum catalyst. Arylallcynes with an ortho substituent, regardless of its electronic nature, directed the silyl substituent mainly to the a-position. PtO2 proved to be a versatile and powerful catalyst compared to H2PtCl6 since it prevents the alkyne reduction.