Enrique Aguilar

Gold-Catalyzed Intermolecular Hetero-Dehydro-Diels-Alder Cycloaddition of Captodative Dienynes with Nitriles : A New Reaction and Regioselective Direct Access to Pyridines

For the first time, nitriles are used as 2pi electron component in a gold-catalyzed intermolecular hetero-dehydro-Diels-Alder cycloaddition with captodative enynes leading to the regioselective formation of pyridines.

First Highly Regio‐ and Diastereoselective [3+2] Cycloaddition of Chiral Nonracemic Alkenyl Fischer Carbene Complexes with Diazomethane Derivatives: Preparation and Synthetic Applications of Enantiomerically Pure Δ2‐Pyrazolines

Enantiomerically pure orthogonally N,N′-diprotected azaprolines 1 and 2,4-diaminoalcohols 2 are readily accessible by [3+2] cycloaddition of (−)-8-phenylmenthol-derived alkenyl Fischer carbene complexes 3 with diazomethane derivatives.

First highly regio- and diastereoselective synthesis of Δ2-pyrazolines by [3+2] cycloaddition of chiral non-racemic Fischer carbene complexes with nitrilimines

Abstract [3+2] Cycloaddition of Fischer carbene complexes with nitrilimines is described for the first time. The “one-pot” conversion of Fischer carbenes into enantiomerically pure Δ 2 -pyrazolines with high regio- and diastereoselectivity is presented as an expeditious route to these compounds.

Catalytic intermolecular hetero-dehydro-Diels-Alder cycloadditions: regio- and diasteroselective synthesis of 5,6-dihydropyridin-2-ones.

A novel catalyzed intermolecular heterodehydro-Diels-Alder reaction between push-pull 1,3-dien-5-ynes and aldimines or silylaldimines is reported. The sequence is promoted both by gold(I) or silver(I) catalysts and leads to the diastereo- and regioselective formation of 5,6-dihydropyridin-2-ones.

First highly regio- and diastereoselective [3+2] cycloaddition of chiral nonracemic Fischer carbene complexes with azomethine ylides: an enantioselective synthesis of (+)-rolipram.

A new procedure for the synthesis of 1,3,4-trisubstituted and 1,4-disubstituted pyrrolidin-2-one derivatives in an enantioselective fashion is reported. The 1,3-dipolar cycloaddition of (+/-)-menthol and (-)-8-phenylmenthol derived Fischer alkoxy alkenyl carbene complexes with in situ generated functionalized azomethine ylides gives the corresponding cycloadducts as chelated tetracarbonyl Fischer carbene complexes. Only one regioisomer is detected in all cases, and the diastereoselectivity of the reaction is very high when (-)-8-phenylmenthol derived carbenes are employed. Oxidation and further transformation of the cycloadducts provide an easy access to pyrrolidin-2-ones. The anti-inflammatory and antidepressant drug (+)-Rolipram is readily prepared in four steps in a 20% overall yield by taking advantage of this newly developed methodology.

α,β-Unsaturated Fischer Carbene Complexes vs. 1,3-Dipoles: Reactions with Nitrones and Nitrilimines

The reaction of tert-butylalkynyl chromium Fischer carbene complex 1 with nitrones 2 affords β-enamino-ketoaldehydes 4 by the light-promoted rearrangement of the corresponding [3+2] cycloadduct carbene complexes 3. On the other hand, [3+2] cycloaddition of chiral nonracemic Fischer alkenyl carbene complexes 19 with nitrilimines 10 yields enantiomerically pure Δ2-pyrazolines with high regio- and diastereoselectivity.

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

1,3-Dien-5-ynes have been extensively used as starting materials for the synthesis of a wide number of different carbo- and heterocycles. The aim of this review is to give an overview of their utility in organic synthesis, highlighting the variety of compounds that can be directly accessed from single reactions over these systems. Thus, cycloaromatization processes are initially commented, followed by reactions directed toward the syntheses of five-membered rings, other carbocycles and, finally, heterocycles. The diverse methodologies that have been developed for the synthesis of each of these types of compounds from 1,3-dien-5-ynes are presented, emphasizing the influence of the reaction conditions and the use of additional reagents in the outcome of the transformations.

Competitive Pathways in the Reaction of Lithium Oxy‐ortho‐quinodimethanes and Fischer Alkoxy Alkynyl Carbene Complexes: Synthesis of Highly Functionalised Seven‐Membered Benzocarbocycles

Up to four different outcomes have been found for the reaction between 1-oxy-ortho-quinodimethanes (oQDMs) and alkoxy alkynyl Fischer carbene complexes (FCCs). The product formed depends on the structure of both reagents and on the reaction solvent. The pathways can be topologically classified as a [4C+2C], a [3(2C+O)+3C], and two different [4C+3C] processes and, in all these sequences, 1-oxy-oQDMs behave as enolates or as vinylogous enolates. The reaction of Choy and Yangs unsubstituted oQDM 1 with tungsten alkynyl FCCs is solvent controlled; thus, selective formation of benzocycloheptenones can be achieved in THF, whereas exclusive synthesis of benzocycloheptene ketals is reached in diethyl ether. On the other hand, THF is the solvent of choice to form benzocycloheptene ketals when an alkyl or aryl group is placed at position 1 of the oQDM in its reaction with tungsten carbene complexes; however, a pyranylidene carbene complex is formed when a chromium carbene complex is used. Alternatively, the presence of bulky alkoxy groups in the FCC component favours a Diels-Alder aromatisation sequence, which leads to 1-naphthyl FCCs. Furthermore, the isolation and the characterisation of several deuterated compounds by labelling experiments have provided some insight into the reaction pathways, and mechanisms consistent with those findings have been established and several reaction intermediates have been identified.

Synthesis and reactivity of β-amino-α,β-unsaturated oxa- and thiazolines

Abstract A simple and efficient route to masked β-amino-α,β-unsaturated acids 3 by reaction of metalated oxa- and thiazolines with nitriles has been developed. The reactivity of 3 has also been explored.

Regioselective synthesis of oxepinones and azepinones by gold-catalyzed cycloisomerization of functionalyzed cyclopropyl alkynes.

A regioselective synthesis of oxepinones and azepinones in good to excellent yields from alkynylcyclopropanecarboxylic acid derivatives is described. This novel cycloisomerization cascade process consists of a nucleophilic addition followed by a cyclopropane ring-opening, where both donor and acceptor groups are required as substituents of the cyclopropane ring.