Luis Casarrubios

RCM in indoles. A new entry to the mitosene skeleton

Abstract The RCM metathesis reaction catalyzed by Grubbs’ ruthenium catalyst is used with a series of 1,2-disubstituted indoles leading with excellent yields to tricyclic compounds. When applied to 1-allyl-2-vinylindoles this methodology allows a new entry to the mitosene skeleton.

Indole and Quinoline Synthesis via Intramolecular Pauson-Khand Reactions of Enamines and Allylamines

Syntheses of indoles and quinolines based upon the Pauson-Khand reaction is described. The starting materials are an aromatic ethynylenamine and ethynylallylamine, which are obtained via Sonogashira coupling. Also, an aromatic ynamine is used for an attempt to synthesize indole.

New protocol for the catalytic Pauson-Khand reaction induced by molecular sieves

Abstract The catalytic Pauson–Khand reaction is favoured in the presence of molecular sieves. This easy protocol probably involves the adsorption of carbon monoxide by the zeolites, making it possible to effect the reaction in the absence of CO atmosphere.

Synthesis of aromatic natural product frameworks using enyne metathesis

Abstract Enynes, easily obtained by the Sonogashira coupling reactions of aromatic iodides, undergo, with good yields, enyne metathesis using the Grubbs catalyst. The resulting dienes are interesting carbo- and heterocycles which can give complex natural frameworks by Diels–Alder reactions. Thus, an estradiol type skeleton is obtained in two steps from the corresponding enynes. An example of a metathesis-Diels–Alder cascade one-pot process is reported.

Preparation of 3,4-enynoindoles via directed lithiation and application to the synthesis of 3,4-carbocycloindoles

Lithiation at C4 of the indole nucleus is readily directed by several functional groups. The 4-substituted indoles thus obtained are transformed into suitable substrates for metathesis reactions. Ring-closing metathesis effected on these compounds lead to skeletons related to several indole alkaloids.

Tandem RCM-Pauson–Khand reaction for access to tricycles in one stepElectronic supplementary information (ESI) available: spectral data and 1H-NMR and 13C-NMR spectra for compounds 8, 10, 11, 14a and 14b. See http://www.rsc.org/suppdata/ob/b3/b302277c

Starting from conveniently designed dienynes complexed to cobalt, a tandem RCM-intramolecular Pauson-Khand reaction yields tricyclic compounds. The methodology allows the synthesis of 6,5,5 and 7,5,5 systems.

Synthesis of ferrocene tethered open and macrocyclic bis-β-lactams and bis-β-amino acid derivatives

New bioorganometallic ferrocene derivatives are synthesized through a Diversity Oriented Synthesis strategy. Easily available ferrocene bisimines have been transformed into open ferrocenyl bis-beta-lactams. These compounds have demonstrated to be versatile synthons used in further transformations into new ferrocene bis-beta-amino acids. Carefully selected substituents submitted to ring closing metathesis (RCM) and Cu-catalyzed oxidative alkyne coupling conditions have also allowed the conversion of open substrates into ferrocenic macrocyclic bis-beta-lactams.

Synthesis, cytotoxic activities and proposed mode of binding of a series of bis([(9-oxo-9,10-dihydroacridine-4-carbonyl)amino]alkyl) alkylamines.

A series of bis([(9-oxo-9,10-dihydroacridine-4-carbonyl)amino]alkyl) alkylamines have been prepared and their antiproliferative properties have been tested against HT-29 cell lines. Compounds 6b and 6d showed an interesting cytotoxic profile and were subjected to further cytotoxic evaluation, DNA binding properties and molecular modelling studies. The evaluation of the cytotoxic activity of compounds 6b and 6d against pairs of cisplatin-sensitive and -resistant ovarian tumour cells shows that both compounds may be endowed with interesting antitumour properties because they are able to circumvent cisplatin resistance in A2780cisR, CH1cisR and Pam 212-ras tumour cells. On the other hand, DNA binding data indicate that compounds 6b and 6d are able to intercalate stronger than acridine within the double helix. Both compounds displace ethidium bromide with an efficiency ten times higher than acridine from several linear double-stranded DNAs and induce 43 degrees unwinding in supercoiled pBR322 DNA while acridine unwinds pBR322 DNA by only 24 degrees. Altogether these data indicate that the significant conformational changes induced by compounds 6b and 6d in the double helix are due to a bis-intercalative DNA binding mode. We propose that binding to DNA through bisintercalation might be at least in part responsible for the remarkable cytotoxic properties of these acridine derivatives. The complex of 6b with d(GCGCGC)(2) in the four possible orientations that the ligand can adopt when binding to the DNA hexamer have been modelled and subjected to molecular dynamics simulations with the aim of evaluating the binding preferences of this bisintercalating agent into the DNA molecule. The predictions suggest that 6b binds to d(GCGCGC)(2) with a parallel orientation of the chromophores relative to each other and with a preference for binding through the minor groove of the hexamer. The possible relevance of these findings to the process of bisintercalation and the antitumour profile of these compounds is discussed in this paper.

Diastereoselective Pauson–Khand reactions on aromatic substrates

Abstract The synthesis of several natural products’ frameworks is carried out by means of a diastereoselective intramolecular Pauson–Khand reaction promoted by molecular sieves. Diastereoselectivity is achieved only if a coordinating group is present at a convenient distance from the alkene moiety. Naphthalenes can be obtained directly under refluxing toluene conditions.

A Click Approach to Polymetallic Chromium(0) and Tungsten(0) Fischer‐Carbene Complexes and Their Use in the Synthesis of Functionalized Polymetallic MetalCarbene Complexes

Alkynylamino Cr(0) and W(0) Fischer carbenes undergo a CuAAC reaction with a diverse range of di-, tri-, and tetra-azides to produce polymetallic chromium(0) and tungsten(0) (Fischer)-carbene complexes in good-to-excellent yields. This method is simple, versatile, and is suitable for the preparation of a diverse range of structures with a high level of symmetry. Moreover, the resulting polymetallic carbene complexes are suitable partners for the peripheral functionalization of the metal nuclei, whilst retaining the metal fragment. This fact has been demonstrated in a simultaneous Pauson-Khand reaction, which, in some cases, allows for the generation of four bicyclic [5,5] rings on the periphery of a tetrametallic molecule in a process that involves the formation of 12 new C-C bonds, with four simultaneous CO-insertion processes. The electrochemistry of the polymetallic Fischer carbenes show completely independent behavior for each nucleus, as well as an anomalous observation of the reversible oxidation of the allyl substituents, which has not been reported before in this class of chemistry.