6 research outputs found
Cobalt-Promoted Dimerization of Aminoquinoline Benzamides
A method
for aminoquinoline-directed, cobalt-promoted dimerization of benzamides
has been developed. Reactions proceed in ethanol solvent in the presence
of MnÂ(OAc)<sub>2</sub> cocatalyst and Na<sub>2</sub>CO<sub>3</sub> base and use oxygen as a terminal oxidant. Bromo, iodo, nitro, ether,
and ester moieties are compatible with the reaction conditions. Cross-coupling
of electronically dissimilar aminoquinoline benzamides proceeds with
modest yields and selectivities
Cobalt-Catalyzed Direct Carbonylation of Aminoquinoline Benzamides
A method for direct carbonylation
of aminoquinoline benzamides
has been developed. Reactions proceed at room temperature in trifluoroethanol
solvent, use oxygen from air as an oxidant, and require MnÂ(OAc)<sub>3</sub> as a cocatalyst. Benzoic and acrylic acid derivatives can
be carbonylated by carbon monoxide affording imides in good yields.
Halogen, nitro, ether, cyano, and ester functional groups are tolerated.
The directing group can be removed under mild conditions affording
phthalimides
Cobalt-Catalyzed, Aminoquinoline-Directed Coupling of sp<sup>2</sup> C–H Bonds with Alkenes
A method
for cobalt-catalyzed, aminoquinoline-directed <i>ortho</i>-functionalization of sp<sup>2</sup> C–H bonds
with alkenes has been developed. Reactions proceed at room temperature
in trifluoroethanol solvent, use oxygen from air as an oxidant, and
require MnÂ(OAc)<sub>3</sub> as a cocatalyst. Benzoic, heteroaromatic,
and acrylic acid aminoquinoline amides react with ethylene as well
as mono- and disubstituted alkenes affording products in good yields.
Excellent functional group tolerance is observed; halogen, nitro,
ether, and unprotected alcohol functionalities are compatible with
the reaction conditions
Tetrahydro-1,3-oxazepines via Intramolecular Amination of Cyclopropylmethyl Cation
An efficient synthesis of tetrahydro-1,3-oxazepines
was developed
involving the regioselective intramolecular amination of cyclopropylmethyl
cation. The cation was generated by the abstraction of one imidate
group in bis-imidate bearing a carbocation-stabilizing substituent.
Using 1,1,2,3-tetrasubstituted cyclopropane substrates, highly diastereoselective
intramolecular amination to <i>trans</i>-tetrahydro-1,3-oxazepines
was achieved. The resulting tetrahydro-1,3-oxazepines were transformed
to the homoallylamine derivatives in high yields
Cobalt-Catalyzed, Aminoquinoline-Directed Functionalization of Phosphinic Amide sp<sup>2</sup> C–H Bonds
In
this paper, we introduce arylphosphinic acid aminoquinoline
amides as competent substrates for cobalt-catalyzed sp<sup>2</sup> C–H bond functionalization. Specifically, the feasibility
of their coupling with alkynes, alkenes, and allyl pivalate has been
demonstrated. Reactions are catalyzed by simple CoÂ(NO<sub>3</sub>)<sub>2</sub> hydrate in ethanol or mixed dioxane/<i>t</i>BuOH
solvent in the presence of MnÂ(OAc)<sub>3</sub>·2H<sub>2</sub>O additive, sodium pivalate, or acetate base and use oxygen from
the air as an oxidant. Directing group removal affords ortho-functionalized <i>P</i>,<i>P-</i>diarylphosphinic acids
Semisynthesis of Libiguin A and Its Analogues by Trans-Lactonization of Phragmalin
Libiguins are limonoids with highly
potent sexual activity enhancing
effects, originally isolated from the Madagascarian Meliaceae species Neobeguea mahafalensis, where they exist in only
minute quantities. Their low natural abundance has hampered mapping
of their biological effects. Here we describe an approach to the semisynthesis
of libiguin A and its close analogues <b>1</b>–<b>3</b> starting from phragmalin, which is a limonoid present in
high amounts in a commercially cultivated Meliaceae species, Chukrasia tabularis, allowing the preparation of
libiguins in appreciable quantities