Metathesis of silicon-containing olefins

Article abstract of DOI:10.1016/0304-5102(92)80152-7

The behaviour of various olefins containing Si-C, Ge-C, Si-Si, Si-H, Si-O-Si and Si-O-C bonds has been studied in the presence of rhenium on alumina metathesis catalysts. Monovinyl-, allyl-, and butenylsilanes bearing alkyl, alkenyl, aryl, aralkyl, silacycloalkyl, siloxane and hydride substituents, as well as unsaturated silacarbon heterocycles, mono- and diallylgermanes, were used as substrates. Heterogeneous Re₂O₇/Al₂O₃-SnBu₄ and Re₂O₇/Al₂O₃-PbEt₄ catalysts showing good activity in metathesis were examined. Except for hydrides, allyl- and butenylsilanes or germanes were active in metathesis regardless of the nature of the substituents at the metal atom. On the other hand, all of the vinylsilanes used were practically inactive in the reaction. Except for vinyl derivatives, metathesis of di- and polyalkenylsilanes, disilanes, disiloxanes and germanes occurred via both intermolecular and intramolecular pathways. These were used to develop a novel effective synthetic method for producing linear 1,4-bis(triorganylsilyl)-(or germyl-) but-2-enes (including those with ferrocenyl substituents at the silicon) and six-membered mono- and disilacycloalkenes, as well as silaspirane structures. It was shown that α-olefin co-metathesis with allylsilanes (followed by protodesilylation) is a convenient method for increasing the length of an α-olefin hydrocarbon chain.