Síntese de compostos N-heterocíclicos via fotocatálise
Resumen
Heterocycles belong to a privileged class of organic compounds that play a
prominent role in chemistry and biology. There is an extensive literature about
methodologies for the synthesis of these substances, showing their importance.
In the last decade, photocatalysis has undergone a substantial expansion driven
by the search for new ways to achieve molecule activation and the growing
interest in the development of more sustainable methodologies. In view of this
scenario, our group has sought to contribute to the progress of photocatalyzed
methodologies, applying photocatalysis to synthesize N-heterocyclic
compounds. In this study, three photocatalytic methodologies were developed,
one employing photoredox catalysis and the others employing photocatalysis by
energy transfer. The first one is described as a cascade cyclization reaction
initiated by alkyl radicals generated via photocatalyzed deamination by visible
light. Under mild reaction conditions, the developed method provides a series of
benzazepinones with a wide substrate scope, good functional group tolerance
and good yields. In the second methodology, the synthesis of
cyclobutanequinolinones was achieved through [2+2] cycloaddition reactions by
energy transfer. The method has also a wide substrate scope, tolerates structural
variations well and produces a large variety of cyclobutane derivatives with yields
ranging from 27-99%, and with excellent regio- and diastereoselectivity. The third
methodology was developed using 1,3-enynes in photocatalyzed reactions. It is
a highly sustainable methodology which employs a metal-free catalyst (1,2,3,5-
tetrakis(carbazol-9-yl)-4,6-dicyanobenzene) (4CzIPN), blue LED as activation
source and a dimethylcarbonate solvent. (DMC). By this method, a series of 1,3-
diene quinolinone derivatives were obtained in excellent yields.
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