Aromatic triazoles have been frequently used as π-conjugated linkers in intramolecular electron transfer processes. To gain a deeper understanding of the electron mediating function of triazoles, we have synthesized a family of new triazole-based electron donor-acceptor conjugates. We have connected porphyrins and fullerenes through a central triazole moiety – (ZnP-Tri-C60) – each with a single change in their connection through the linker. An extensive photophysical and computational investigation reveals that the electron transfer dynamics – charge separation and charge recombination – in the different ZnP-Tri-C60 conjugates reflect a significant influence of the connectivity at the triazole linker. Except for m4m-ZnP-Tri-C60 17, the conjugates exhibit through-bond electron transfer with varying rate constants. Since the through-bond distance is nearly equal in the ZnP-Tri-C60 conjugates, the variation in charge separation and charge recombination dynamics is mainly associated with the electronic properties of the conjugates, including orbital energies, electron affinity, and the energies of the excited states. The changes of the electronic couplings are, in turn, a consequence of the different connectivity patterns at the triazole moieties.
The bis-tetrahydroisoquinoline (bis-THIQ) natural products have been studied intensively over the past four decades for their exceptionally potent anticancer activity, in addition to strong Gram-positive and Gram-negative antibiotic character. Synthetic strategies toward these complex polycyclic compounds have relied heavily on electrophilic aromatic chemistry, such as the Pictet–Spengler reaction, that mimics their biosynthetic pathways. Herein, we report an approach to two bis-THIQ natural products, jorunnamycin A and jorumycin, that instead harnesses the power of modern transition-metal catalysis for the three major bond-forming events and proceeds with high efficiency (15 and 16 steps, respectively). By breaking from biomimicry, this strategy allows for the preparation of a more diverse set of nonnatural analogs.
An insertion of arenes
into both imides and anhydrides via reactive
aryne intermediates is presented. The reaction is performed under
exceptionally mild conditions, and the corresponding ketoamide products
are amenable to derivatization to deliver a variety of synthetically
useful motifs such as quinolones, indoles, and ketoanilines.
A catalytic method for the decarboxylative coupling of 2-(azaaryl)carboxylates with aryl halides is described. The decarboxylative cross-coupling presented is mediated by a system catalytic in both palladium and copper without requiring stoichiometric amounts of organometallic reagents or organoboronic acids. This method circumvents additional synthetic steps required to prepare 2-azaaryl organometallics and organoborates as nucleophilic coupling partners, which are prone to protodemetallation and protodeborylation and produce potentially toxic byproducts.
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