The cycloaddition reactions of unsaturated esters with cyclopentadiene on γ-alumina

Pagni, Richard M.; Kabalka, George W.; Hondrogiannis, George; Bains, Satinder; Anosike, Peter; Kurt, Robert

doi:10.1016/s0040-4020(01)80418-x

Cited by 30 publications

(16 citation statements)

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“…Hydrogen bonding has also been reported to play an important role,71p,71q as shown in the relationship between the acceptor number (AN) of the solvent and the Diels−Alder reaction rates 12m,12o…”

Section: The Role Of Water and Catalystmentioning

confidence: 99%

Recent Advances in Lewis Acid Catalyzed Diels−Alder Reactions in Aqueous Media

et al. 2001

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Recently the aqueous medium has attracted the interest of organic chemists, and many, sometimes surprising, discoveries have been made. Among the organic reactions investigated in aqueous medium, the Diels−Alder cycloaddition has been the most widely studied because of its great importance [a] (left) was born in Perugia in 1936. He received his laurea in Industrial Chemistry from the University of Milano in 1963. He then moved as research associate to the University of Perugia, where he became full professor of Organic Chemistry in 1975. He was a postdoctoral co-worker at the University of La Jolla -California. His current research interests are in the fields of enantioselective synthesis and organic reactions in water. Oriana Piermatti (second from left) was born in Valtopina (Perugia) in 1968. She received her laurea in Chemistry in 1991 and her Ph.D. in 1996 at the University of Perugia, working with Prof. Fringuelli on the stereoselective synthesis of β-hydroxy acids. She is currently working as a post-doctoral research fellow on the synthesis of new chiral auxiliaries and catalysts and their application in asymmetric synthesis. Ferdinando Pizzo (second from right) was born in Viterbo in 1951. He received his laurea in 1975. In 1986 he spent a year with E. Wenkert at the University of California at S. Diego working on the metal decomposition of 2-diazoacylfurans. He is now associate professor at the University of Perugia. His current research is the study of reactivity and stereoselectivity of organic reactions in water. Luigi Vaccaro (right) was born in Cava dei Tirreni (Salerno) in 1972. He studied at the University of Napoli Ϫ Federico II where he received his laurea in 1996. In the same year, he joined the group of Prof. Fringuelli at the University of Perugia, where he obtained his Ph.D. in 1999, working on organic reactions in water. He is undertaking postdoctoral research on Lewis acid catalysis in water at the University of Perugia.MICROREVIEWS: This feature introduces the readers to the authors' research through a concise overview of the selected topic. Reference to important work from others in the field is included.

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Section: The Role Of Water and Catalystmentioning

confidence: 99%

Recent Advances in Lewis Acid Catalyzed Diels−Alder Reactions in Aqueous Media

et al. 2001

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“…Other factors that have been studied with the aim of increasing the rate and stereoselectivity of Diels-Alder reactions include external pressure [19], ultrasound irradiation [20], and catalytic effects exercised by clays [21], alumina [22], silica gels [23], microporous organic crystals [24], antibodies [25], cyclodextrins [26,27], and supramolecular assemblies [28,29]. By far the most effective enhancements of rate and selectivity are induced by Lewis acids [30][31][32][33].…”

Section: Figmentioning

confidence: 99%

Diels-Alder Reactions in Micellar Media

Otto¹,

Engberts

2001

Surfactant Science

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I. INTRODUCTION TO DIELS-ALDER REACTIONS The Diels-Alder reaction is a [4+2]cycloaddition in which a diene (four-π component) reacts with a dienophile (two-π component) to provide a six-membered ring (Fig. 1). Six new stereocenters are formed in a single reaction step. Because the conformations of the double bonds are usually fully retained, the reaction is stereospecific and consequently the absolute configuration of the two newly formed asymmetric centers can be controlled efficiently. The Diels-Alder reaction is of great value in organic synthesis and is a key step in the construction of compounds containing six-membered rings [1]. A historic account of this important conversion has been published by Berson [2]. Homo Diels-Alder reactions involve only hydrocarbon fragments. If the diene or dienophile possesses heteroatoms in any of the positions a-f (Fig. 1), heterocyclic ring systems are formed (hetero Diels-Alder reactions). Normal electron demand Diels-Alder reactions are promoted by electron-donating substituents in the diene and electron-withdrawing substituents in the dienophile. The opposite situation applies for inverse electron demand Diels-Alder reactions. Neutral Diels-Alder reactions are accelerated by both electron-withdrawing and electron-donating substituents.

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“…Pagni et al 25 , em 1993, estudaram a reação entre acrilato de metila (1) e ciclopentadieno (2) sobre aluminas de várias atividades, ressaltando que a proporção massa:massa entre os reagentes e a alumina causa mudança significativa na diastereosseletividade endo:exo da reação (Tabela 2). Os resultados apresentados na Tabela 2 mostram que quando a proporção massa:massa entre os reagentes e a alumina é inferior a 1:2,5, a razão endo:exo permanece praticamente constante, enquanto que quando a massa de reagentes torna-se inferior à massa de alumina, a razão endo:exo passa a acompanhar o aumento da proporção massa:massa.…”

Section: Produtos Porcentagem (%)unclassified

“…No ano seguinte, Dols et al 31 estudaram a reação entre 4-acetoxiciclopentenona (22) e ciclopentadieno (2), na presença de diferentes ácidos de Lewis. A subseqüente eliminação induzida por base do grupo β-acetóxi a partir dos adutos (23) ou (24) levou à triciclo enona (25), conforme Esquema 8. É interessante notar que a rota aparentemente mais direta para o produto (25) seria através da cicloadição entre ciclopentadienona e ciclopentadieno, entretanto, esta não foi a escolhida, pois o dienófilo utilizado nesse caso, ciclopentadienona, tem forte tendência a polimerizar.…”

Section: Reações De Diels-alder Em Condições Homogêneasunclassified

“…Exemplificando, na presença de cloreto de alumínio, a reação ocorreu rapidamente, fornecendo diretamente o produto (25) com 61% de rendimento. Entretanto, com um ácido de Lewis mais fraco, como cloreto de zinco, obtiveram-se os adutos (23) e (24) na proporção de 3:1, os quais após o tratamento com uma solução 1 mol.L -1 de hidróxido de potássio forneceram o produto (25). A proporção maior do aduto (23) pode ser racionalizada, em termos de efeito estérico, ou seja, o estado de transição que leva ao aduto (24) apresenta maior impedimento estérico do que foi aquele encontrado em 23 Outros dienos menos reativos do que o ciclopentadieno, tais como cicloexadieno e 2,3-dimetilbutadieno, foram testados, porém nessas reações houve a necessidade do emprego de altas pressões, além do uso de ácidos de Lewis.…”

Section: Reações De Diels-alder Em Condições Homogêneasunclassified

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