Question

Question: Show how the following starting material is converted to the given product by a series of two pericyclic reactions. Account for the observed stereochemistry.

Short answer

Answer

Step-by-step solution

Electrocyclic reaction

The reactions that involve the conversion of a pi bond of a conjugated system to a sigma bond or vice-versa are named electrocyclic reactions.

Conjugated systems involving an even number of pi electrons undergo conrotation, while conjugated systems with an odd number of pi electrons undergo disrotation under thermal conditions.

Preparation of the given product

The conversion of the starting material to the given product involves two main steps:

• 8 pi electrocyclic ring-opening (conrotatory) and
• 6 pi electrocyclic ring-opening (conrotatory).

The reactions are shown below.

Reactions involved in the formation of the product