Journal of Molecular Catalysis A-Chemical, Vol.190, No.1-2, 9-25, 2002
Synthesis of six-membered cyclic siloxanes via enyne metathesis with a ruthenium catalyst generated in situ
The catalytic system in situ generated by combination of [RuCl2(p-cymene)](2) as a ruthenium source, 1,3-bis(mesityl)imidazolinium chloride (MesH(2)ImCl) as a bulky electron-releasing carbene precursor and cesium carbonate as a base, is shown to be an efficient catalyst for the metathesis reaction of propargylic allylsilyl ethers R-1-C=CCR2-O-SiMe2-CH2CH=CH2. The metathesis products, the cyclic siloxanes, were obtained after complete conversion of the enynes in 67-87% isolated yields. These six-membered ring compounds contain the 1,3-diene unit that is used in Diels-Alder reaction and give access to heterobicyclic derivatives. The resulting cyclic siloxanes are selectively opened under oxidative conditions with H2O2 to afford allylic diols, with fluoride to form conjugated triene and under hydrogenation conditions with Pd/C catalyst to give a tetrasubstituted alkene. (C) 2002 Elsevier Science B.V. All rights reserved.