Toluene/methane, cross metathesis

Scheme 36 (a) H/D exchange, (b) alkane hydrogenolysis, (c) alkane metathesis, (d) cross-metathesis of toluene/ethane, (e) cross-metathesis of propane/methane. 

This reaction can be exploited to carry out the cross-metathesis of toluene and ethane to give ethylbenzene and xylenes (Scheme 36(d)) or that of methane and propane to yield two ethanes (Scheme 36(0)). ... 

Cross metathesis between two different alkanes represent one of the most difficult challenges in organic chemistry [53]. In 2001, Basset et al. first demonstrated the possibilities of sigma bond metathesis between two different alkanes [55]. In 2004, this same group has reported the cross metathesis between ethane and toluene [81] and methane and propane [82]. Silica-supported tantalum hydride catalyst [(=SiO)2TaH] [(=SiO)2TaH3] was employed for cross-metathesis reaction between toluene and ethane at 250°C. Under static condition, it produced mainly ethyl benzene and xylenes as major product along with propane and methane (Scheme 24). 

Scheme 25 Possible mechanism of cross metathesis of toluene and methane with silica-supported tantalum tris-hydride...

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