Enrique Aller

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

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.