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- Title
2-[(1E,3E)-4-Arylbuta-1,3-dien-1-yl]-4H-chromen-4-ones as Dienes in Diels-Alder Reactions - Experimental and Computational Studies.
- Authors
Albuquerque, Hélio M. T.; Santos, Clementina M. M.; Lima, Carlos F. R. A. C.; Santos, Luís M. N. B. F.; Cavaleiro, José A. S.; Silva, Artur M. S.
- Abstract
The synthesis and reactivity of 2-[(1E,3E)-4-arylbuta-1,3-dien-1-yl]-4H-chromen-4-ones as dienes in Diels-Alder (DA) reactions with several electron-poor and electron-rich dienophiles under microwave irradiation was studied. The optimized reaction conditions were achieved with N-methylmaleimide as the dienophile and Sc(OTf)3 (OTf = triflate) as a Lewis acid under microwave-assisted and solvent-free conditions. The Lewis acid improved the reaction yields as it prevented the adducts obtained from undergoing a second DA reaction; thus, the formation of a bisadduct was avoided. The α,β:γ,δ-diene of the starting chromones was the most reactive, and the computational results confirmed the experimental findings. Theoretical calculations also provided a rationale for the unexpected lack of reactivity shown by some dienophiles. The adducts prepared were dehydrogenated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ); however, the aza adducts were sensitive to the highly energetic reaction conditions necessary for the aromatization.
- Subjects
RING formation (Chemistry); HETEROCYCLIC compounds; MICROWAVE chemistry; LEWIS acids; DIELS-Alder reaction
- Publication
European Journal of Organic Chemistry, 2017, Vol 2017, Issue 1, p87
- ISSN
1434-193X
- Publication type
Article
- DOI
10.1002/ejoc.201601072