Retro-Diels-Alder Reactions of Masked Cyclopentadienones Catalyzed by Heterogeneous Brønsted Acids

• Published in: Advanced synthesis & catalysis 2010-12, Vol.352 (18), p.3419-3430
• Main Authors: Demuynck, Anneleen L. W., Levecque, Pieter, Kidane, Aklilu, Gammon, David W., Sickle, Eugene, Jacobs, Pierre A., De Vos, Dirk E., Sels, Bert F.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Cyclopentadiene; cyclopentenones; Derivatives; heterogeneous catalysis; Optimization; retro-Diels-Alder reaction; Screening; Synthesis; Zeolites
• ISSN: 1615-4150; 1615-4169; 1615-4169
• DOI: 10.1002/adsc.201000571

The zeolite H‐Beta catalyzes the retro‐Diels–Alder reaction of a range of cyclopentadiene cyclo‐adducts at moderate temperatures and ambient pressure, in the presence of an active dienophile. The active catalyst was identified and optimum reaction conditions established after screening a range of zeolites in the retro‐Diels–Alder reaction of the cyclopentadiene adduct of cyclopentenone. Our results suggest that retro‐Diels–Alder reactions of tricyclodecadienones are catalyzed by Brønsted acids and the high catalytic performance of H‐Beta catalysts can be ascribed to the optimal balance between the number of acid sites and their strength as well as to the accessibility of these sites. The methodology was then applied to a series of alkyl derivatives of cyclopentadienylcyclopentenones to provide a viable alternative synthetic route to 4‐alkylcyclopentenones and the versatility of the approach was demonstrated by the successful cycloreversion of N‐cyclohexyl‐2‐azanorborn‐5‐ene.