| dc.description.abstract | Morita Baylis-Hillman (MBH) reaction a carbon-carbon bond forming reaction
between an α,β-unsaturated carbonyl and aldehydes or activated ketones in the presence
of a nucleophilic catalyst. The MBH reaction is an atom-economical method of rapid
increase of molecular complexity. The development of this process has received
considerable attention in recent years. This dissertation presents the development of a
new catalytic system for the symmetric and asymmetric MBH reaction. The new system
for the racemic version of this reaction was accomplished employing a 1:1:1 ratio of
catalytic amounts (10 mol%) of MgI2, TMEDA and DMAP and proved to be highly
effective. For the asymmetric version was developed a highly enantio-selective system
based on Fu’s planar chiral DMAP derivative (II) with ee´s up to 98%. Abnormal MBH
adducts are obtained employing either ethyl 2,3-butadienoate or ethyl propiolate in good
yields, in the presence if MgI2 and either a tertiary amine or phosphine as the
nucleophile. The α,β-unsaturated carbonyls where prepared by a modified direct α-
methylenation using paraformaldehyde, diisopropylammonium trifluoroacetate, and
catalytic acid or base with excellent yields for several carbonyls compounds.
The Negishi cross-coupling reaction is the Pd or Ni-catalyzed stereoselective
cross-coupling or organozincs and aryl-, alkenyl-, or alkynyl halides. Enantioselective
Negishi cross-coupling of aryl zincs and α-bromo ketones was accomplished employing
a NCN Pincer complex as the catalyst with ee´s up 99%. The required pincer complexes
have been prepared by the oxidative addition of pincer ligands with palladium or nickel.
Additionally, It has been developed a direct and highly active, (NCN)-Pd
catalytic system for the α-arylation of ketones with a variety of aryl bromides using the
air and moisture stable [t-BuPheBox-Me2]PdBr (XVI) as the catalyst. The adducts are
obtained in excellent yields (92% average for 20 examples) in only 1 hour using 1 mol%
of catalyst loading. Perhaps more importantly, the work described here shows that XVI
is highly reactive, highly selective, even on substrates bearing challenging functional
groups such alkenes. | en |
