On the relationship between structure and reaction rate in olefin ring-closing metathesis

In the RCM reactions of a series of simple α,ω-dienes, the relative order of reactivity has been unambiguously detd. showing that cyclohexene forms faster than cyclopentene or cycloheptene. 1,5-Hexadiene inhibits the RCM of 1,7-octadiene; 1,5-hexadiene cannot progress to the RCM product (cyclobutene) but forms an unexpectedly stable cyclic η2-complex