Chapter 24, Problem 24.27P

Interpretation Introduction

Interpretation:

We mentioned in the chapter opener (p. 1198) that tetrodotoxin has been synthesized using a Diels–Alder reaction. The one incorporated in the synthesis by M. Isobe involved the following diene and dienophile. The curved arrow notation for the specified reaction is to be drawn.

Concept introduction:

The Diels-Alder reaction is the cycloaddition of diene and dienophile. The diene has a pair of conjugate double and contributes its $\text{4π}$ electrons. The dienophile has single double bond and contributes its $\text{2π}$ electrons. These six electrons must flow in a cyclic fashion. Three curved arrows are drawn cyclically to account for the movement of six electrons. The reaction proceeds through a cyclic transition state, which makes it a pericyclic reaction. Therefore, the Diels-Alder reaction is called $\text{[4+2]}$ cycloaddition.