Angeles Lorenzo

Iminophosphorane-mediated annelation of a pyridine ring into a preformed pyridine one: synthesis of naphthyridine, pyrido[1,2-c]pyrimidine and pyrido[1,2-c]quinazoline derivatives

Abstract Aza Wittig-type reaction of iminophosphoranes 2 and 6, prepared from 4- and 3-formylpyridines by sequential treatment with ethyl azido acetate and triphenylphosphine, with isocyanides leads to 2,7-naphthyridine, 4, 1,7-naphthyridine 7 and 2,6-naphthyridine 8 respectively. Iminophosphoranes 10 and 22 undergo pyrido annelation by reaction with isocyanates, carbon dioxide, carbon disulfide and acyl chlorides to give pyrido[1,2-c]pyrimidine 11–14 and pyrido[1,2-c]quinazoline derivatives 23–26.

Pyrido annelation reaction by a tandem aza Wittig/electrocyclic ring-closure strategy: Preparation of pyrazolo[4,3-c]- and pyrazolo[3,4-c]pyridine derivatives.

Abstract The aza Wittig-type reaction of iminophosphorane 3 , prepared from 5-formyl-1-phenylpyrazole by sequential treatment with ethyl azidoacetate and triphenylphosphine, with isocyanates, ketenes, aldehydes and carbon disulfide leads to the functionalized pyrazolo[4,3-c]pyridines 5,7,9 and 11 respectively. Iminophosphorane 15 , prepared from 4-formyl-1-phenylpyrazole, under goes pyrido annelation by reaction with ketenes to give the isomeric pyrazolo[3,4-c]pyridines 22 in modest yields.

New synthetic applications of vinyliminophosphoranes based on the reactivity of the vinyl side chain

Abstract New reactions of vinyliminophosphoranes involving either the β-carbon atom of the vinyl side chain as nucleophilic center or the α-carbon as electrophilic center are described

Bis(iminophosphorane)-mediated 1,2,4-triazolo-annulation on imidazole and benzimidazole rings. Preparation of imidazo [1,2-b]-1,2,4-triazoles and 1,2,4-triazolo [1,5-a] benzimidazoles

Aza Wittig-type reactions of bis(iminophosphoranes) derived from 1,2-diaminoimidazole and 1,2-diaminobenzimidazole with isocyanates and aroyl chlorides afforded imidazo[1,2-b]-1,2,4-triazoles or 1,2,4-triazolo[1,5-a]benzimidazoles, respectively

Fused mesoionic heterocycles: synthesis of 1,2,4-triazolo(4,3-b)-1,2,4-triazole derivatives

Abstract A number of mesoionic compounds derivatives of the bicyclic system 1,2,4-triazolo(4,3-b)-1,2,4-triazole have been prepared from 4-amino-1-methyl-3,5-bis(methylthio)-1,2,4-triazolium iodide and aryl isothiocyanates.

Preparation and thermal behaviour of 1-substituted 2-dicyanomethylene-1,2-dihydropyridines: Synthesis of 2-pyridyl malononitriles.

Abstract 1-Substituted 2-methylthio-4,6-diphenylpyridinium iodides ( 2 ) react with malononitrile under the influence of bases to give 1-substituted 1,2-dihydropyridines ( 3 ), which by thermal treatment can be converted into 2-pyridyl malononitriles (4).

Preparation and reactivity of mesoionic 1,2,4-triazolo-[4,3-b]-1,2,4-triazole derivatives

Abstract A number of mesoionic compounds (2) derivatives of the 1,2,4-triazolo[4,3- b ]-1,2,4-triazole ring system have been prepared from 4-amino-1 -methyl -3,5-bis(methylthio)- 1,2,4-triazolium cation and aryl isothiocyanates. Compounds ((2) react with methyl iodide to give the methiodides ((3) which undergo ring opening to the monocyclic compounds ((4) through sulfur extrusion under thermal conditions. Methiodides ((3) by sequential treatment with malononitriIe and hydrochloric acid lead to the pyrazolo[5,1- c ]-1,2,4-triazole (6).

An anomalous intramolecular conjugate addition of N-protected imidazoles to vinyliminophosphoranes promoted by tetrabutylammonium fluoride. X-Ray crystal structure of 5-ethoxycarbonyl-5-(triphenylphosphoranylidene-amino)-5,6-dihydroimidazo[2,1-α]isoquinoline

Abstract An anomalous intramolecular conjugate addition of N-SEM protected imidazoles to vinyliminophosphoranes proceeds efficiently in the presence of tetrabutylammonium fluoride (TBAF) to afford the corresponding fused imidazoles. The crystal and molecular structure of 4 have been solved by X-Ray analysis. The crystal packing is governed by weak C-H…X (X=O, N or aromatic π system) hydrogen interactions because the absence of more polarized donor groups to form hydrogen bonds.