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Alcaide B.,Grupo de Lactamas y Heterociclos Bioactivos | Almendros P.,Institute Quimica Organica General | Fernandez I.,Complutense University of Madrid | Del Campo T.M.,Grupo de Lactamas y Heterociclos Bioactivos | Naranjo T.,Grupo de Lactamas y Heterociclos Bioactivos
Chemistry - A European Journal | Year: 2015

The divergent behavior of two homologue allenals, namely, 2-(buta-2,3-dienyloxy)- and 2-(propa-1,2-dienyloxy)benzaldehydes, as cyclization substrates is described. 2-(Buta-2,3-dienyloxy)benzaldehydes suffers a formal allenic carbocyclization reaction to afford chromenes, whereas 2-(propa-1,2-dienyloxy)benzaldehydes react to yield chromones. The formation of chromenes is strictly a formal hydroarylation process divided into two parts, namely, allenic Claisen-type rearrangement and oxycyclization. An unknown N-heterocyclic carbene (NHC)-catalyzed allenic hydroacylation reaction must be invoked to account for the preparation of chromones. ortho-Allenylbenzaldehydes bearing either electron-donating substituents or electron-withdrawing substituents worked well to afford both the hydroarylation and hydroacylation products. This unexpected difference in reactivity can be rationalized by means of density functional theory calculations. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Alcaide B.,Grupo de Lactamas y Heterociclos Bioactivos | Almendros P.,Institute Quimica Organica General | Luna A.,Grupo de Lactamas y Heterociclos Bioactivos | Gomez-Campillos G.,Grupo de Lactamas y Heterociclos Bioactivos | Torres M.R.,Complutense University of Madrid
Journal of Organic Chemistry | Year: 2012

Lactam-tethered allenols, readily prepared from α-oxolactams, were used as starting materials for divergent reactivity with selenenylating reagents. Either oxycyclization (spirocyclic selenolactams) or ring expansion (selenoquinolones) can be achieved through the choice of both reagents and substrates. The biological activity of some of the synthesized heterocycles has additionally been evaluated in four human cancer cell lines. © 2012 American Chemical Society.


Alcaide B.,Grupo de Lactamas y Heterociclos Bioactivos | Almendros P.,Institute Quimica Organica General | Alonso J.M.,Grupo de Lactamas y Heterociclos Bioactivos
Molecules | Year: 2011

The last decade has witnessed dramatic growth in the number of reactions catalyzed by gold complexes because of their powerful soft Lewis acid nature. In particular, the gold-catalyzed activation of propargylic compounds has progressively emerged in recent years. Some of these gold-catalyzed reactions in alkynes have been optimized and show significant utility in organic synthesis. Thus, apart from significant methodology work, in the meantime gold-catalyzed cyclizations in alkynol derivatives have become an efficient tool in total synthesis. However, there is a lack of specific review articles covering the joined importance of both gold salts and alkynol-based compounds for the synthesis of natural products and derivatives. The aim of this Review is to survey the chemistry of alkynol derivatives under gold-catalyzed cyclization conditions and its utility in total synthesis, concentrating on the advances that have been made in the last decade, and in particular in the last quinquennium. © 2011 by The Authors.

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