this system showed >80% formation of polymeric products with cyclic oligomers
(C 16 , C 24 , C 3 , and C 40 ) of cyclooctane.
4.3.1 Metathesis of Cyclooctane
Precatalyst 27 has shown surprising results in the metathesis of cyclooctane and
cyclodecane with broad distribution of lower and higher macrocyclic alkanes.
Cyclopentane, cyclohexane, and cycloheptane were found to be inactive under
similar condition [79].
For example, the cyclooctane metathesis using 27 has shown exceptional distribution of macrocyclic alkanes in the range of C 12 to C 40 without any polymeric
products [79], wherein the cyclooctane undergoes similar mechanism with C–H
bond activation followed by β-H elimination to give W-methylidene hydride and
cyclooctene. The cyclooctene undergoes ring-opening–ring-closing metathesis
reactions (RO-RCM) via the backbiting of terminal double bond to give
1,9-cyclohexadecadiene. This on hydrogenation gives the cyclohexadecane
(Scheme 21). In a similar manner, macrocyclic alkanes (C 24 , C 32 , C 40 ) are generated via RO-RCM of cyclooctene.
Scheme 21 Proposed mechanism for metathesis of cyclooctane into cyclohexadecane
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M.K. Samantaray et al.