Asymmetric organocatalytic anthrone additions to activated alkenes
2011; Elsevier BV; Volume: 67; Issue: 14 Linguagem: Inglês
10.1016/j.tet.2011.02.032
ISSN1464-5416
AutoresAlex Zea, Andrea‐Nekane R. Alba, Natalia Bravo, Albert Moyano, Ramón Rios,
Tópico(s)Oxidative Organic Chemistry Reactions
ResumoAsymmetric organocatalytic additions of anthrones to activated alkenes are discussed. The reaction between anthrone or dithranol and α,β-unsaturated aldehydes is catalyzed by diphenylprolinol trimethylsilyl ether in toluene at −40 °C, giving the Michael adducts with good yields and enantioselectivities. Bifunctional amino-thioureas efficiently catalyze the additions of anthrones to both nitroalkenes and maleimides, and high enantioselectivities can be achieved in both instances at room temperature. In the case of nitroalkenes, a Michael addition takes exclusively place. Anthrone generally gives Diels–Alder cycloadducts in the reaction with maleimides, while dithranol affords the Michael adducts. Transition state working models in which the bifunctional catalyst binds simultaneously to the alkene and to the anthrone enolate account for the stereochemical outcome of these additions.
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