Question

The following conversion, carried out in the presence of Grubbs catalyst and ethylene gas, involves a cascade of metathesis reactions. Draw a reaction sequence that illustrates how the reactant is converted to the product Z, and indicate where each labeled atom in the reactant ends up in Z.

Short answer

Answer

Step-by-step solution

Grubb’s catalyst

Grubb’s catalyst is a complex catalyst containing a ruthenium transition metal connected to a carbene group. The pi-bond between carbon and ruthenium is the site of the catalytic activity. This catalyst allows trans-alkylidenation reaction among olefins. It is also used as a catalyst for ring-closing metathesis (RCM).

Consider the activity of the Grubb’s catalyst in the given compound.

Trans-alkyldenation

Grubb’s catalyst allows the exchange of substituents between the complex olefin and ethylene molecule. This is followed by a ring-opening reaction to form the required compound.