β,β-tripyrrin-bridged earring porphyrins were synthesized through Suzuki-Miyaura cross coupling reactions. These porphyrinoids have multiple cavities and can accommodate two or three metal ions per molecule. The structures of the porphyrins have been elucidated by x-ray diffraction analysis, and feature curved π planes. The electronic spectra of the porphyrins exhibit near-infrared (NIR) absorptions and metal insertion leads to red-shifted and intensified absorption features. Electrochemical analysis and transient absorption measurements indicated that the porphyrins exhibit effective electronic communication between their central and peripheral moieties.
Ar eaction sequence of regioselective peripheral bromination, Suzuki-Miyaura coupling with 2-borylated thiophene or pyrrole,and oxidative ring-closure with FeCl 3 allowed the synthesis of heterole-fused earring porphyrins 4Pd and 9Pd from the parent earring porphyrin 1.Differently pyrrole-fused porphyrins 5H and 6H and their Pd II complexes 5Pd and 6Pd were also synthesized.T he structures of 4Pd, 5H, 6Pd,a nd 8Pd have been revealed by X-rayanalysis to be slightly twisted owingtoconstraints imposed by heterole-fused structures. 5Pd exhibits an intensified band at 1505 nm, while 4Pd and 9Pd displays mall but remarkably red-shifted absorption bands reaching around 2200 nm.
Enantioselective transformations
of olefins are among the most
important strategies for the asymmetric synthesis of organic compounds.
Chemo-, diastereo-, and stereoselective control of reactions with
internal acyclic alkenes for the construction of functionalized acyclic
alkanes still remain a persistent challenge. Here, we report a palladium-catalyzed
asymmetric regiodivergent Heck-type diarylation of internal acyclic
alkenes. The 1,2-diarylation of two accessible acyclic alkenes, cinnamyl
carbamates and enamides with diazonium salts and aromatic boronic
acids, furnishes products containing vicinal stereogenic centers via
the stereospecific formation of carbonyl coordination-assisted transient
palladacycles. Moreover, the asymmetric migratory diarylation of enamides
enables the formation of incontiguous stereocenters by an interrupted
diastereoselective 1,3-chain-walking process. This protocol streamlines
access to highly functionalized multisubstituted enantioenriched carbamates
and amine derivatives which are embedded in the key biologically active
motifs.
Herein
we report a Pd-catalyzed C–N bond cleavage strategy
for the cycloaddition of pyrrolidines with azlactones or butenolides
to construct the azepines. Leverage of the readily accessible 3-alkylidenepyrrolidine
can serve as an effective precursor for zwitterionic salts. The in
situ formation of an allyl-palladium intermediate through the cleavage
of inert, cyclic C–N bonds leads to a cascade [5 + 2] cycloaddition,
which allows for the diverse synthesis of azepine scaffolds with good
functional group tolerance and 100% atom economy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.