Question

The Robinson Annulation Lab.

Question 1. Using arrow formalisms, write out the full mechnism of the reaction. (The Robinson Annulation)

Answer 1

The first step in the process is the Michael Addition to an α,β-unsaturated ketone, such as methyl vinyl ketone (ethyl vinyl ketone is shown above):

The newly formed enolate intermediate must first tautomerize for the conversion to continue:

The subsequent cyclization via Aldol Addition is followed by a condensation to form a six-membered ring enone:

The Robinson Annulation can also proceed under acidic catalysis, with the entire process occurring in one pot, as shown below. The use of a precursor of the α,β-unsaturated ketone, such as a β-chloroketone, can reduce the steady-state concentration of enone and decrease the side reaction of polymerization..