[WBr2(CO)2(diene)]/AlCl2Et mixts. promote metathesis of cis-2-pentene to give 2-butene and 3-hexene. For diene = norbornadiene, the reaction is catalytic, and is accompanied by cis to trans isomerization of the 2-pentene, whereas for diene = 1,5-cyclooctadiene or cyclooctatetraene, the metathesis is essentially stoichiometric. The same complexes catalyze the metathesis of trans-2-pentene to give 2-butene and 3-hexene, but at approx. twice the rate obsd. for the cis-alkene. [WBr2(CO)2(diene)]/AlCl2Et mixts. also catalyze the metathesis of 1,7-octadiene to give cyclohexene and ethene. The intermediacy of metal carbene derivs. in such reactions is supported by the reactions of [WBr2(CO)2(norbornadiene)] with alkylating agents SiMe4 and MeMgBr which give methane, whereas [WBr2(CO)2(norbornadiene)] and AlCl2Et in the absence of alkenes gave virtually stoichiometric amts. of ethane.
Alkene metathesis catalyzed by [WBr2(CO)2(diene)]/AlCl2Et
VASAPOLLO, Giuseppe;
1989-01-01
Abstract
[WBr2(CO)2(diene)]/AlCl2Et mixts. promote metathesis of cis-2-pentene to give 2-butene and 3-hexene. For diene = norbornadiene, the reaction is catalytic, and is accompanied by cis to trans isomerization of the 2-pentene, whereas for diene = 1,5-cyclooctadiene or cyclooctatetraene, the metathesis is essentially stoichiometric. The same complexes catalyze the metathesis of trans-2-pentene to give 2-butene and 3-hexene, but at approx. twice the rate obsd. for the cis-alkene. [WBr2(CO)2(diene)]/AlCl2Et mixts. also catalyze the metathesis of 1,7-octadiene to give cyclohexene and ethene. The intermediacy of metal carbene derivs. in such reactions is supported by the reactions of [WBr2(CO)2(norbornadiene)] with alkylating agents SiMe4 and MeMgBr which give methane, whereas [WBr2(CO)2(norbornadiene)] and AlCl2Et in the absence of alkenes gave virtually stoichiometric amts. of ethane.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
