Fotoacoplamiento y fotorreducción de iminas. Aplicaciones sintéticas y estudio mecanístico

Autor: Ortega Martínez-Losa, María; 

Tipo de documento: Tesis

Director/es: Campos García, Pedro JoséRodríguez Barranco, Miguel Angel

Universidad: Universidad de La Rioja

Año: 2005 

Texto completo open access 

Resumen: In the present work the photochemistry of imines has been studied, particularly, the photocoupling and photoreduction reactions to yield 1,2-diamines and monoamines, respectively. In this sense, it is worthy to underline that these nitrogen compounds are very important in the field of biological, medicinal and synthetic applications. At a first step, a new one-pot method for the synthesis of 1,2-diamines has been developed. This methodology, which involves the photoreduction of imines using catalytic amounts of zinc as a photosensitizer, allows an efficient synthesis and selective separation of meso and d,l compounds on a multigram scale. Subsequently, it has been studied the photoreduction of different imines bearing a hydrogen atom, alkyl or aryl groups leads to the corresponding monoamines through a new and versatile approach that is compatible with the environment. Moreover, we have modulated, for the first time, the photoreduction of aldimines to obtain secondary amines as reaction products instead of vicinal diamines. Likewise, the irradiation of a variety of bifunctional imines has demonstrated that photoreduction of the carbon-nitrogen double bond is chemoselective in the presence of other functional groups such as ester and cyano groups. Interestedly, the reduction of chiral imino esters led to enantiopure amino esters that can be easily converted into the corresponding a-amino acids, thus providing a new method for the synthesis of this kind of compound. Finally, different studies to elucidate the mechanism of this reaction were carried out. In this context, we were proposed that the photoreduction process (with o without coupling) involves the formation of triplets species which progress giving radical species by hydrogen abstraction of the alcoholic solvent.