We report herein the photoinduced isomerization of a
series of
arylidene heterocycles 1. The photoreaction mechanism
was investigated by a combined UV–vis/photo-NMR spectroscopic
study, and we showed that Ar-TZDs exhibit a positive P-type photochromism,
which limits their isomerization efficiency. By exploring the solvatochromism
in a series of solvents, the conditions favoring the conversion toward
one or the other stereoisomer have been studied, in particular by
choosing the appropriate wavelengths. Finally, the extension of this
photoisomerization study was proposed with a convenient preparation
of various fused heterocyclic quinolines in good overall yields.
Optically active amphiphilic compounds derived from N-methylephedrine, N-methylprolinol, or cinchona derivatives possessing bromide or chiral lactate counterions were efficiently used as protective agents for rhodium(0) nanoparticles. The full characterization of these surfactants and the obtained nanocatalysts was performed by means of different techniques. These spherical nanoparticles, with sizes between 0.8-2.5 nm depending on the stabilizer, were evaluated in the hydrogenation of model substrates in neat water as a green solvent. The rhodium catalysts showed relevant kinetic properties, but modest enantiomeric excess values of up to 13 % in the hydrogenation of ethyl pyruvate. They were also investigated in the hydrogenation of disubstituted arenes, such as m-methylanisole, providing interesting catalytic activities and a preferential cis selectivity of around 80 %; however, no asymmetric induction was observed.
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