Raquel P. Herrera

Crossed Intramolecular Rauhut−Currier-Type Reactions via Dienamine Activation

The intramolecular Rauhut-Currier reaction creates a carbon-carbon bond between two tethered Michael acceptors. Previous asymmetric versions have relied on 1,4-additions of chiral nucleophilic catalysts. Herein, we investigate a novel strategy that involves the formation of electron rich dienamines as key intermediates. Our methodology provides an efficient entry to the iridoid framework.

Enantioselective α-and γ-alkylation of α,β- unsaturated aldehydes using dienamine activation

The enantioselective alkylation of α,β-unsaturated aldehydes with stabilized carbocations as electrophiles via the activation as dienamine intermediates is described. This unique application of dienamine catalysis allows for the first enantioselective γ-alkylation of linear α,β-unsubstituted enals.

Organocatalytic Enantioselective Henry Reactions

A large number of interesting organocatalytic enantioselective protocols have been explored and successfully applied in the last decade. Among them, the Henry (nitroaldol) reaction represents a powerful carbon-carbon bond-forming procedure for the preparation of valuable synthetic intermediates, such as enantioenriched nitro alcohols, which can be further transformed in a number of important nitrogen and oxygen-containing compounds. This area of research is still in expansion and a more complex version of this useful process has recently emerged, the domino Michael/Henry protocol, affording highly functionalized cycles with multiple stereogenic centers.

On the Mechanism of Arene‐Catalyzed Lithiation: The Role of Arene Dianions—Naphthalene Radical Anion versus Naphthalene Dianion

The use of lithium and a catalytic amount of an arene is a well-established methodology for the preparation of organolithium reagents that manifest greater reactivity than the classical lithium-arene solutions. In order to rationalize this conduct, the participation of a highly reduced species, the dianion, is proposed and its reactivity explored. Studies of kinetics and of distribution of products reveal that the electron-transfer (ET) reactivity profile of dilithium naphthalenide in its reaction with organic chlorides excludes alternative mechanisms of halogen-lithium exchange. The process generates organolithium compounds. The dianion thus emerges along with the radical anion as a suitable candidate for catalytic cycles in certain processes. Endowed with a higher redox potential than its radical anion counterpart, dilithium naphthalene displays a broader spectrum of reactivity and so increases the range of substrates suitable for lithiation. The reaction of dilithium naphthalene with THF is one example of the divergent reactivity of the radical anion and the dianion, which has been the source of apparent misinterpretation of results in the past and has now been appropriately addressed.

Isatin as a Strategic Motif for Asymmetric Catalysis

We thank the Ministry of Science and Innovation (CTQ2010-19606-C02-01) and Aragon Government (E-10) for financial support of our research. R.H. and S.M. thank the Iranian Government for their fellowships and financial support.

On the mechanism of the naphthalene-catalysed lithiation: the role of the naphthalene dianion

Abstract Kinetic and distribution product studies on naphthalene-catalysed lithiation reactions of chlorinated precursors have shown the probable participation of a naphthalene dianion (dilithium naphthalene) as the very active electron carrier agent in the chlorine–lithium exchange process.

The Role of the Indole in Important Organocatalytic Enantioselective Friedel-Crafts Alkylation Reactions

With the development of catalytic asymmetric methodologies directed to the synthesis of biologically active molecules during the last years, organocatalysis has emerged as a powerful tool. The organocatalytic approach is comple- mentary to transition metal-based catalysis within the field of asymmetric synthesis and several research groups have achieved great aims in this area by the first time. The enantioselective Friedel-Crafts alkylation reaction of indoles is a powerful and direct method for preparing enantiomerically pure 3- or 2-substituted indolyl compounds and a number of organocatalyzed syntheses of these indolyl substrates have been developed in recent years. Due to the abundance of indole moieties in enantiomerically pure biologically interesting natural compounds asymmetric strategies have arisen as impor- tant processes of synthesis. These important alkylation processes including the addition of indole to � ,� -unsaturated car- bonyl compounds, nitroalkenes and imines as well as their applications will be discussed in this review.

Thiourea catalyzed organocatalytic enantioselective Michael addition of diphenyl phosphite to nitroalkenes

Bifunctional thiourea catalyzes the enantioselective Michael addition reaction of diphenyl phosphite to nitroalkenes. This methodology provides a facile access to enantiomerically enriched β-nitrophosphonates, precursors for the preparation of synthetically and biologically useful β-aminophosphonic acids. DFT level of computational calculations invoke the attack of the diphenyl phosphite to the nitroolefin by the Re face, this give light to this scarcely explored process update in the literature. The computational calculations support the absolute configuration obtained in the final adducts.

Multicomponent reactions : concepts and applications for design and synthesis

• Illustrates the crucial role and the important utility of multicomponent reactions (MCRs) to organic syntheses • Compiles novel and efficient synthetic multicomponent procedures to give readers a complete picture of this class of organic reactions • Helps readers to design efficient and practical transformations using multicomponent reaction strategies • Describes reaction background, applications to synthesize complex molecules and drugs, and reaction mechanisms

On the dichotomy of the SN2/ET reaction pathways: an apparent SN2 reactivity in the reaction of naphthalene dianion with alkyl fluorides

Abstract Dilithium naphthalene (Li2C10H8) displays a SN2 reactivity profile in its reaction with alkyl fluorides (n-, s- and t-octyl fluoride). SN2 seems to be the dominant mechanism operating with primary alkyl fluorides, which presumably turns into competition with ET as we move to secondary and tertiary alkyl fluorides. Significantly, lithium naphthalene (LiC10H8) seems to have also an important nucleophilic component when reacting with alkyl fluorides, in contrast to the previously proposed general ET process valid for all alkyl halides. These results explain the observed distribution of products and are reinforced by a complete analysis of the products originated by the reaction with 6-halohexenyl radical probes, whose main alkylation products are described here for the first time.