We report the development of a stereoselective
method for the allylation
of ketones utilizing N-substituted allyl equivalents
generated from a chiral allenamide. By choice of the appropriate ligand
for the Cu-catalyst, high linear selectivity can be obtained with
good diastereocontrol. This methodology allows access to chiral γ-hydroxyaldehyde
equivalents that were applied in the synthesis of chiral γ-lactones
and 2,5-disubstitued tetrahydrofurans.
We report the development of a stereoselective method
for the allylation
of ketones utilizing N-substituted allyl equivalents generated from
a chiral allenamide. By employing N-heterocyclic carbenes as ligands
for the Cu catalyst, good branched selectivity can be obtained with
high diastereocontrol. This methodology allows access to a catalytically
generated, polarity-reversed (umpolung) allyl nucleophile to enable
the preparation of chiral 1,2-aminoalcohol synthons containing a dissonant
functional group relationship.
Chiral γ-lactones are prevalent
organic architectures found
in a large array of natural products. In this work, we disclose the
development of a modified catalytic system utilizing a commercially
available Cu-phosphite catalyst for the diastereoselective reductive
coupling of chiral allenamides and ketones to afford chiral γ-lactone
precursors in 80:20 to 99:1 dr.
Herein, we report the development of a Cu-catalyzed enantioselective
borylative aminoallylation of aldehydes using a N-substituted allene
to access boryl-substituted 1,2-aminoalcohol synthons for diversification
to chiral heteroatom-rich organic compounds. The reported reaction
provides access to several different substitution patterns of chiral
1,2-aminoalcohol products from the same readily available starting
materials with high diastereo- and enantioselectivity.
The Suzuki–Miyaura cross-coupling reaction of 2-bromo-1,3-bis(trifluoromethyl)benzene with arylboronic acids was evaluated and determined to suffer from the formation of large amounts of boronic acid homocoupling products in conjunction with dehalogenation. Homocoupling product formation in this process likely occurs through a rare protonolysis/second transmetalation event rather than by the well-established mechanism requiring the involvement of O2. The scope of this boronic acid homocoupling reaction was investigated and shown to predominate with electron-deficient arylboronic acids. Finally, a good yield of cross-coupling products could be obtained by employing dicyclohexyl(2′,6′-dimethoxybiphenyl-2-yl)phosphine (SPhos) as the ligand.
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