Commercially available liquid enol ethers and acetates as gaseous alkyne equivalents in cationic Rh(I)/BINAP-catalyzed chemo- and regioselective formal cross-alkyne cyclotrimerizations
作者:Hiromi Hara、Masao Hirano、Ken Tanaka
DOI:10.1016/j.tet.2009.02.047
日期:2009.6
A cationicrhodium(I)/BINAPcomplex catalyzes partial intramolecular [2+2+2] cycloadditions of 1,6- and 1,7-diynes with enol ethers or a ketene acetal giving substituted benzenes in good yields. The same catalyst also catalyzes complete intermolecular [2+2+2] cycloadditions of two different monoynes with enol acetates giving tri- and tetrasubstituted benzenes in good yields with complete regioselectivity
e under catalysis by PdCl2(PhCN)2. The same imines were formed almost quantitatively by noncatalyzed reaction of the azide with the corresponding vinylic ethers. The rate of the catalyzed reaction was found to be first order each in the allylic ether and in the azide. Easiness of the imine formation from the allylic ethers depended on the nature of azide, decreasing in the order of N3SO2Me>N3CO2Me>N3Ph