16 research outputs found
Triflic Acid Catalyzed Oxidative Lactonization and Diacetoxylation of Alkenes Using Peroxyacids as Oxidants
A clean and efficient diacetoxylation reaction of alkenes
catalyzed
by triflic acid using commercially available peroxyacids as the oxidants
has been developed. This method was also applied in oxidative lactonizations
of unsaturated carboxylic acids in good to high yields
Aerobic Acetoxyhydroxylation of Alkenes Co-catalyzed by Organic Nitrite and Palladium
An
aerobic acetoxyhydroxylation of alkenes cooperatively catalyzed
by organic nitrite and palladium at room temperature using clean and
cheap air as the sole oxidant has been developed. Various vicinal
diols, diacetoxyalkanes, and dihalogenoalkanes have been synthesized.
The gram-scale synthesis has also been approached. Vicinal difluorination
and dichlorolation products have also been achieved via this reaction
Organopromoted Selectivity-Switchable Synthesis of Polyketones
In this work, an
organopromoted metal-free pharmaceutical-oriented
selectivity-switchable benzylic oxidation was developed, affording
mono-, di-, and trioxygenation products, respectively, using oxygen
as the oxidant under mild conditions. This process facilitates dioxygenation
of 2,6-benzylic positions of heterocycles, which could be inhibited
by heterocycle chelation to the metal cocatalysts. Enantiopure chiral
ketones could also be prepared. The noninvolvement of transition metals
and toxins avoids metal or hazardous residues, consequently ensuring
a final-stage gram-scale synthesis of Lenperone
Direct Wittig Olefination of Alcohols
A base-promoted
transition metal-free approach to substituted alkenes
using alcohols under aerobic conditions using air as the inexpensive
and clean oxidant is described. Aldehydes are relatively difficult
to handle compared to corresponding alcohols due to their volatility
and penchant to polymerize and autoxidize. Wittig ylides are easily
oxidized to aldehydes and consequently form homo-olefination products.
By the strategy of simultaneously in situ generation of ylides and
aldehydes, for the first time, alcohols are directly transferred to
olefins with no need of prepreparation of either aldehydes or ylides.
Thus, the di/monocontrollable olefination of diols is accomplished.
This synthetically practical method has been applied in the gram-scale
synthesis of pharmaceuticals, such as DMU-212 and resveratrol from
alcohols
Transition-Metal-Free Hydrogenation of Aryl Halides: From Alcohol to Aldehyde
A transition-metal-
and catalyst-free hydrogenation of aryl halides,
promoted by bases with either aldehydes or alcohols, is described.
One equivalent of benzaldehyde affords an equal yield as that of 0.5
equiv of benzyl alcohol. The kinetic study reveals that the initial
rate of PhCHO is much faster than that of BnOH, in the ratio of nearly
4:1. The radical trapping experiments indicate the radical nature
of this reaction. Based on the kinetic study, trapping and KIE experiments,
and control experiments, a tentative mechanism is proposed. As a consequence,
a wide range of (hetero)Âaryl iodides and bromides were efficiently
reduced to their corresponding (hetero)Âarenes. Thus, for the first
time, aldehydes are directly used as hydrogen source instead of other
well-established alcohol–hydrogen sources
Synthesis of Highly Functionalized Indoles and Indolones via Selectivity-Switchable Olefinations
Highly
functionalized indoles and indolones were prepared via selectivity-switchable
mono- or diolefinations. The Julia olefination of the products followed
by a Brønsted acid-prompted cyclization afforded indolones, whereas
the indoles were obtained by a sequential Wittig olefination and electrocyclization.
This method opens divergent access to highly functionalized nitrogen-containing
bicyclic or tricyclic heterocycles
Transalkylation via C–N Bond Cleavage of Amines Catalyzed by Super Organophotoreductant CBZ6
The super organoreductant CBZ6-catalyzed tandem transalkylation–cyclization
using amines as traceless radical donors and stabilizer is reported.
The later-stage breaking of an N–C bond enables the transalkylation
with a secondary amine as the leaving moiety. A wide range of tertiary
amines were used as alkyl radical donors for the C1–C8 alkyls.
This traceless stabilizer also enabled the transalkylation with methyl
radical, which is normally not possible because of the instability
of methyl radical
Direct Alkylation of Amines with Alcohols Catalyzed by Base
A base-catalyzed/promoted
transition-metal-free direct alkylation
of amines with alcohols has been developed, giving the desired amines
in generally high yields from either aromatic or aliphatic alcohols.
On the basis of the <sup>1</sup>H NMR and in situ IR (React-IR) monitoring
experiments, isotope-labeling experiments, as well as control experiments,
a novel “hemiaminal” model is proposed to understand
the mechanism, which explains the formation of the “extra”
aldehyde in the reaction
Pharmaceutical-Oriented Selective Synthesis of Mononitriles and Dinitriles Directly from Methyl(hetero)arenes: Access to Chiral Nitriles and Citalopram
A pharmaceutical-oriented, transition-metal-free,
cyanide-free
one-step direct transformation of methylarenes to aryl nitriles is
described. For the dimethylarenes, the selectivity can be well-controlled
to form mononitriles or dinitriles. Enantioenriched nitriles can also
be synthesized by this method. As a pharmaceutically practical method,
the antidepressant drug citalopram was synthesized from cheap and
commercially abundant <i>m</i>-xylene on a gram scale in
high yield, avoiding transition-metal residues and toxic cyanides
Ru-Catalyzed Rearrangement of <i>N</i>‑Methyl Isoxazolidines to <i>N</i>–H 1,3‑Oxazinanes: A Strategy of Self-Hydride Transferring Cleavage of N–O Bonds
A strategy of ruthenium-catalyzed
self-hydride transferring cleavage
of N–O bonds was designed and utilized in a cascade 1,3-dipolar
cyclization of alkenes and <i>N</i>-methyl nitrones followed
by an <i>N</i>-demethylative rearrangement, furnishing synthetically
useful <i>N</i>–H 1,3-oxazinanes