Diels-Alder Reaction
The Diels-Alder reaction is a conjugate addition reaction of a conjugated diene to an alkene (the di enophile) to produce a cyclohexene. The simplest example is the reaction of 1,3-butadiene with ethene to form cyclohexene
The analogous reaction of 1,3-butadiene with ethyne to form 1,4-cyclo hexadiene is also known:
Since the reaction forms a cyclic product, via a cyclic transition state, it can also be described as a “cyclo addition”. The reaction is a concerted process:
Due to the high degree of regio- and stereoselectivity (due to the concerted mechanism), the Diels-Alder reaction is a very powerful reaction and is widely used in synthetic organic chemistry. The reaction usually thermodynamically favourable due to the conversion of 2 --bonds into 2 new stronger -bonds. The two reactions shown above require harsh reaction conditions, but the normal Diels-Alder reaction is favoured by electron withdrawing groups on the electrophilic dienophile and by electron donating groups on the nucleophilic diene.
examples of the components are shown below:
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