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5697231 
Book/Book Chapter 
4.5 - Retrograde Diels–Alder Reactions 
Sweger, RW; Czarnik, AW 
1991 
Pergamon 
Oxford 
Comprehensive Organic Synthesis 
551-592 
The retro Diels-Alder (Rda) reaction is a π2s+σ2s+σ2s electrocyclic process that, as the name implies, is the reverse of the familiar Diels–Alder cycloaddition reaction. A kinetic study of the prototypical Rda reaction, conversion of cyclohexene to 1,3-butadiene and ethylene (equation 1), has been studied in the temperature range of 541–629°C.1 Some early observations of Rda reactions were made in 1906 by Albrecht, who reported that the DA adducts of cyclopentadiene with benzoquinone dissociate at their melting points,2 and in 1929 by Diels and Alder, who reported the dissociation of a furan-maleic anhydride adduct at its melting point.3 Alder used the reaction as a test to differentiate between acetylenedicarboxylic ester adducts of cyclopentadiene and of cyclohexadiene;4 heating the latter adduct eliminates ethylene, while heating the former yields only the starting diene and dienophile (the Alder-Rickert rule). Perhaps the earliest use of the Rda reaction in a synthetic mode was in the preparation of acetylenedicarbonyl chloride,5 in which an anthracene adduct was used as a removable acetylene protecting group. Use of the Rda reaction in achieving selective synthetic conversions has been reviewed several times to date. 
Fleming, Ian