Miguel Tomas

Pyridine Activation via Copper(I)-Catalyzed Annulation toward Indolizines

The copper(I)-catalyzed regioselective [3 + 2] cyclization of pyridines toward alkenyldiazoacetates leading to functionalized indolizine derivatives is reported. A broad range of pyridine derivatives (including quinoline and isoquinoline) is compatible with this cyclization reaction. The process represents the first successful example of metal-catalyzed cyclization of a π-deficient heterocyclic system with alkenyldiazo compounds.

Cu(I)-catalyzed regioselective synthesis of polysubstituted furans from propargylic esters via postulated (2-furyl)carbene complexes.

Polysubstituted furan derivatives are regioselective obtained from (bis-alkynyl)methyl carboxylates in the presence of catalytic amounts of copper(I) salts. This multistep process is consistent with the intermediacy of a copper(I) (2-furyl)carbene complex which is intercepted by suitable trapping reagents.

Asymmetric C2-C3 Cyclopentannulation of the Indole Ring

Chiral nonracemic alkynyl(alkoxy)carbene complexes of tungsten(0) undergo the [3 + 2] cyclization toward alpha-methylindoles and 1,6-dimethyl-1,2,3,4-tetrahydropyridine to provide 2,3-indoline-fused cyclopentenone and 2,3-piperidine-fused cyclopentenone skeletons, respectively, with very high enantiomeric purities (96-99% ee).

Cesium fluoride induced desilylation reaction of immonium salts derived from vinylogous amides

Abstract The cesium fluoride induced desilylation reaction of immonium salts derived from amides, thioamides and vinylogous amides provides access to reactive azomethine ylides in synthetically useful yields.

Regioselective Synthesis of 4,6,7-Trisubstituted Benzofurans from Furfural Imines and Nonheteroatom Stabilized Alkynylcarbene Complexes

Nonheteroatom stabilized chromium alkynylcarbene complexes 3,6, generated in situ from Fischer cabene complexes 1, smoothly react with furan-2-ylmethanimines 4 to provide substituted 7-aminobenzofurans 5 in moderate to good yields. The procedure involves the construction of the arene ring by a regioselective [3+3] carbocyclization reaction.

The first [4 + 3] annulation of Fischer carbene complexes with azadienes: facile synthesis of azepines

The reaction of 3-iminoprop-1-enylamines 1 with pentacarbonyl(1-methoxyprop-2-enylidene)chromium(0) complexes leads stereoselectively to substituted 5H-6,7-dihydroazepines in high yields; the process takes place at low temperature and is thought to involve a tandem imine cyclopropanation–Cope rearrangement.

Carbene and silicon routes toward a simple nitrile ylide. Spectroscopic, kinetic, and chemical characterization

Trimethylsilylmethyl-tri?at (I) reagiert mit Acetonitril und Thiophenol (III) zu dem Phenylthio-silylimidat (IV), das mit Silber- fluorid zum Methylnitril-Ylid (V) gespalten wird.

Direct Access to β-Oxodiazo Compounds by Copper(II)-Catalyzed Oxidative Rearrangement of Stabilized Vinyl Diazo Derivatives

The copper(II)-catalyzed reaction of alkenyldiazo compounds with iodosylbenzene leading to β-oxodiazo derivatives is reported. This process occurs via an unprecedented 1,2-shift of the diazoacetate function. A selection of the synthetic applications of a representative member of this new class of functionalized diazo derivatives in the regioselective synthesis of substituted 1,4-dicarbonyl compounds is also reported.

One-pot, two-step synthesis of substituted anthraquinones from chromium(0) alkynyl carbenes and isobenzofurans.

The reaction of alkynyl Fischer carbenes and isobenzofurans gives rise to the corresponding [4 + 2] cycloadducts. The newly formed carbene adducts are suitable for benzannulation processes in the presence of tert-butylisocyanide or carbon monoxide to yield a variety of new highly substituted polycyclic structures having the anthraquinone framework. The whole two-step process is conducted in a one-pot fashion from easily available 1,4-dihydro-1,4-epoxynaphthalenes.

Stereoselective cyclopropanation of 1-azadienes with Fischer carbene complexes

1-Aza-1,3-dienes, including a 1-aza-1,3,5-triene, are cyclopropanated by pentacarbonyl(methoxy)phenylchromium to give trans-cyclopropaneimines stereoselectively; their transformation into cyclopropane aldehydes and five-membered heterocycles is also described.