The Diels-Alder reaction: doomed to academic praise only?
SOFIE SEGHERS1, JORIS W. THYBAUT2, CHRISTIAN V. STEVENS1*
*Corresponding author
1. SynBioC Research Group, Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Belgium
2. Laboratory for Chemical Technology, Department of Materials, Textiles, and Chemical Engineering, Faculty of Engineering and Architecture, Ghent University, Belgium
Abstract
The Diels-Alder reaction is universally acknowledged for its atom-efficient and simple access to molecular complexity. This textbook example of a green reaction forms one of the most efficient routes towards six-membered rings. However, a large gap is noticed between the relevance and versatility in the academic world, implying a small scale, and industrial use. Obviously, the current developed Diels-Alder procedures are failing to make their way into industry. This perspective paper will gave a critical overview of the most important bottlenecks of Diels-Alder reactions. Flow chemistry, a key research area for green engineering, is a powerful tool to facilitate a safe transfer of Diels Alder processes to the industrial environment.
INTRODUCTION
A unique and powerful chemistry was discovered in 1928,(1) which has been studied vigorously ever since. The Diels-Alder (DA) reaction is a prominent type of pericyclic processes, that is, a reaction that takes place in a single step, without intermediates, via cyclic redistribution of bonding electrons. In this [4+2]cycloaddition, two new σ-bonds are introduced to form a six-membered ring. Typically, a mixture of endo- and exo-isomers is obtained. The endo products, however, are mostly obtained as the major products due to favourable secondary orbital interactions (2).
The DA reaction gained a strong position in organic synthesis at an astonishing speed. The widespread acknowledged utility rests on its broad scope and the ability to form six-membered rings and molecules which are otherwise difficultly accessible, such as bridged bicyclic compounds. However, a large gap is noticed between the relevance and versatility in the academic world, implying a small scale, and industrial use. Obviously, the current developed Diels-Alder procedures are failing to make their way into industry. The insurmountable bar ...
