Q27E - Organic Chemistry (Mcmurry)

Question

Two sequential pericyclic reactions are involved in the following furan synthesis. Identify them, and propose a mechanism for the transformation.

Step-by-Step Solution

Answer

To identify the two pericyclic reactions which involved in the furan synthesis can be stated.

Step 1: Statement for the first reaction

The involvement for the first pericyclic reaction is the cycloaddition (4+2) reaction. There is only one electron pair of alkyne which takes place in reaction but is not involved in the carbonyl group. The alkyne’s KOMO and diene’s LUMO are best for bonding and occurred by suprafacial pathways under thermal conditions.

Step 2: Statement for the second reaction

The second pericyclic reaction which involved in reverse cycloaddition (4+2) reaction process. It can be occurred with a pathway of suprafacial under thermal condition. Phenyl cyanide elimination will leads to the product.