22 research outputs found
Synthesis of Enantioenriched α,α-Dichloro- and α,α-Difluoro-β-Hydroxy Esters and Amides by Ruthenium-Catalyzed Asymmetric Transfer Hydrogenation
A mild and convenient approach was
developed to prepare a series
of α,α-dihalogeno β-hydroxy esters or amides by
using commercially available Noyori’s complex [RuCl(<i>p</i>-cymene)(<i>R</i>,<i>R</i>)-TsDPEN]
as a catalyst (S/C = 100−200) in the asymmetric transfer hydrogenation
of the corresponding ketones. Moderate to high yields (up to 99%)
and excellent enantioselectivities (up to >99% ee) were achieved
for
a series of variously substituted dichloro and difluoro β-hydroxy
esters and amides
Ruthenium-Catalyzed [2 + 2 + 2] Cycloaddition Reaction Forming 2‑Aminopyridine Derivatives from α,ω-Diynes and Cyanamides
A novel, efficient,
and mild synthetic route for the preparation
of 2-aminopyridines via ruthenium-mediated [2 + 2 + 2] cycloaddition
of α,ω-diynes and cyanamides has been developed. This
atom-economical catalytic process demonstrated remarkable regioselectivities
to access pyridine derivatives of high synthetic utility
HNTf<sub>2</sub>‑Catalyzed Regioselective Preparation of Polysubstituted Naphthalene Derivatives Through Alkyne–Aldehyde Coupling
We report herein
the preparation of polysubstituted naphthalene
derivatives by the original Brønsted-acid-catalyzed benzannulation
reaction of phenylacetaldehydes with alkynes. This reaction, which
was usually performed with Lewis acids under thermal activation, is
efficiently promoted by 15 mol % of triflimide (HNTf<sub>2</sub>)
at room temperature under metal-free and mild reaction conditions
and leads with a perfect regioselectivity to a wide variety of diversely
functionalized naphthalenes in 41–78% yield. A catalytic cycle
is proposed together with some further applications of this catalytic
system in the related benzannulation transformations of epoxide and
acetal derivatives
Access toward Fluorenone Derivatives through Solvent-Free Ruthenium Trichloride Mediated [2 + 2 + 2] Cycloadditions
An efficient and
practical route for the preparation of highly
substituted fluorenones and analogues via solvent-free ruthenium trichloride
mediated [2 + 2 + 2] cycloaddition of α,ω-diynes and alkynes
has been developed. This green chemistry approach involves a solventless
and atom-economical catalytic process to generate densely functionalized
fluorenones and related derivatives of high synthetic utility
Enantioselective Synthesis of 1-Aryl-tetrahydroisoquinolines through Iridium Catalyzed Asymmetric Hydrogenation
Asymmetric hydrogenation of 1-aryl-3,4-dihydroisoquinolines using the [IrCODCl]<sub>2</sub>/(<i>R</i>)-3,5-diMe-Synphos catalyst is reported. Under mild reaction conditions, this atom-economical process provides easy access to a variety of enantioenriched 1-aryl-1,2,3,4-tetrahydroisoquinoline derivatives, which are important pharmacophores found in several pharmaceutical drug candidates, in high yields and enantiomeric excesses up to 99% after a single crystallization
Synthesis and Antiproliferative and Metabolic Evaluations of Novel Securinine Derivatives
New securinine analogues have been
prepared by semisynthesis. Two
series were developed using either Suzuki or Sonogashira cross coupling
reactions. The <i>in vitro</i> cytotoxicity of the compounds
was assayed against HCT-116 colon cancer cells. The most potent derivatives
showed promising growth inhibition on four tumoral cell lines giving
a valuable insight on the structure–activity relationship (SAR)
of securinine. Moreover, high antiproliferative effect against A-375
(melanoma) was observed with IC<sub>50</sub> up to 60 nM
Palladium-Catalyzed Efficient Enantioselective Synthesis of Chiral Allenes: Steric and Electronic Effects of Ligands
Asymmetric synthesis of chiral allenes
starting from prochiral
substrates under mild reaction conditions promoted by Pd-SYNPHOS catalyst
is reported. This protocol provides an efficient access to various
enantioenriched aryl- and alkyl- substituted allenes, which are versatile
building blocks of high utility to both organic and medicinal chemists,
in excellent isolated yields (up to 96%) and high enatiomeric ratio
values (up to 95:5). In addition, a comparative study using several <i>C</i><sub>2</sub>-symmetric atropisomeric diphosphine ligands
revealed the overwhelming impact of the steric and electronic properties
of the ligands for the catalytic efficiency of this process
Enantioselective Rhodium-Catalyzed Synthesis of α-Chloromethylene-γ-Butyrolactams from <i>N</i>-Allylic Alkynamides
The first enantioselective cycloisomerization with intramolecular halogen migration of various 1,6-enynes promoted by a cationic Rh-Synphos catalyst is reported. This method provides an efficient route to enantiomerically enriched γ-butyrolactam derivatives, which are important core scaffolds found in numerous natural products and biologically active molecules. Good yields and enantiomeric excesses up to 96% are achieved
Heck Coupling Using a Vinyliodo-MIDA Boronate: An Efficient and Modular Access to Polyene Frameworks
A simple Heck coupling between an
alkenyl iodo-boronate and a variety
of terminal olefins is disclosed. This method gives access to a wide
range of dienic moieties including valuable bis-functionalized dienes.
The synthetic potential of the coupling reaction is demonstrated by
a short and modular preparation of several tetraenic compounds
Palladium(0)-Catalyzed Dearomative [3 + 2] Cycloaddition of 3‑Nitroindoles with Vinylcyclopropanes: An Entry to Stereodefined 2,3-Fused Cyclopentannulated Indoline Derivatives
The palladium(0)-catalyzed
diastereoselective dearomative cyclopentannulation
of 3-nitroindoles with vinylcyclopropanes is described. This straightforward
and highly atom-economical method leads to a wide range of functionalized
indolines in good yields and diastereoselectivities and represents
an unprecedented entry toward the valuable 2,3-fused cyclopentannulated
indoline scaffold