# Enhanced Reactivity for the Wagner-Jauregg Reaction Under Aqueous Conditions

## TL;DR

This paper improves the Wagner-Jauregg reaction by enabling it to work efficiently under mild, aqueous conditions, making it a more practical tool for chemical synthesis.

## Contribution

The study introduces aqueous, low-temperature conditions that enhance the reaction's selectivity and yield for the Diels–Alder-ene product.

## Key findings

- Aqueous conditions enable the Wagner-Jauregg reaction to proceed at lower temperatures with high selectivity.
- Electron-poor dienes can now be used effectively in the reaction under optimized conditions.
- The study clarifies the influence of steric and electronic factors on product selectivity in [4 + 2]-cycloadditions.

## Abstract

The Wagner-Jauregg
reaction produces up to four new carbon–carbon
bonds and eight new stereocenters, but limitations, such as high requisite
temperatures, a restricted substrate scope, and significant undesired
polymer formation, have resulted in this reaction receiving minimal
attention. While generally considered a subtype of the Diels–Alder
reaction, in which a styrenyl diene is employed in a tandem double-Diels–Alder
reaction, a second, structurally distinct, stereochemically complex
product can also be produced by the Wagner-Jauregg reaction, resulting
from a Diels–Alder-ene cascade. Very few attempts to improve
reaction conditions, expand substrate scope, or optimize product selectivity
have been published. Through reaction optimization, supplemented by
density functional theory calculations, we have explored the role
of diene, dienophile, and solvent in controlling both the yields and
product selectivity. This has led to the discovery of lower-temperature,
aqueous reaction conditions that can produce the Diels–Alder-ene
product, even with electron-poor dienes, with high selectivity and
good yield. This work expands the understanding of the steric and
electronic factors influencing product selectivity in [4 + 2]-cycloadditions
and upgrades the reaction from a historical curiosity to a practical
synthetic tool.