Site-Selective C-H Functionalization of (Hetero)Arenes via Transient, Non-Symmetric Iodanes.

A strategy for C-H functionalization of arenes and heteroarenes has been developed to allow site-selective incorporation of various anions, including Cl, Br, OMs, OTs, and OTf. This approach is enabled by generation of reactive, non-symmetric iodanes by combining anions and bench-stable PhI(OAc). The utility of this mechanism is demonstrated via -selective chlorination of medicinally relevant arenes, as well as site-selective C-H chlorination of heteroarenes.

Ketyl radical reactivity via atom transfer catalysis.

Single-electron reduction of a carbonyl to a ketyl enables access to a polarity-reversed platform of reactivity for this cornerstone functional group. However, the synthetic utility of the ketyl radical is hindered by the strong reductants necessary for its generation, which also limit its reactivity to net reductive mechanisms. We report a strategy for net redox-neutral generation and reaction of ketyl radicals.

Synthesis of Expanded Porphyrinoids with Azulene and Indene Subunits and an opp-Dioxadicarbaporphyrin from Fulvene Carbinols and a Dioxacarbatripyrrin.

In an attempt to prepare quatyrin derivatives, which are hydrocarbon analogues of the porphyrins, azulene-appended fulvene carbinols were self-condensed in the presence of BF·EtO. Although these investigations failed to give structures related to quatyrin, expanded porphyrin analogues were obtained instead. In dichloromethane, the major macrocyclic product consisted of three fulvene units, but when chloroform was used as the reaction solvent, a tetrafulvene macrocycle was isolated.

Catalytic Alkene Difunctionalization via Imidate Radicals.

The first catalytic strategy to harness imidate radicals has been developed. This approach enables alkene difunctionalization of allyl alcohols by photocatalytic reduction of their oxime imidates. The ensuing imidate radicals undergo consecutive intra- and intermolecular reactions to afford (i) hydroamination, (ii) aminoalkylation, or (iii) aminoarylation, via three distinct radical mechanisms.

Triiodide-Mediated δ-Amination of Secondary C-H Bonds.

The Cδ -H amination of unactivated, secondary C-H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3 (-) )-mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2 ) as I3 (-) , this approach precludes undesired I2 -mediated decomposition which can otherwise limit synthetic utility to only weak C(sp(3) )-H bonds. The mechanism of this triiodide-mediated cyclization of unbiased, secondary C(sp(3) )-H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates.

Synthesis and metalation of dimethoxybenziporphyrins, thiabenziporphyrins, and dibenziporphyrins.

Dimethoxybenzitripyrranes were prepared in excellent yields by reacting benzene dicarbinols with BF3·Et2O and excess pyrrole in refluxing 1,2-dichloroethane. Reaction with a pyrrole dialdehyde in the presence of TFA, followed by oxidation with DDQ, afforded good yields of meso-diphenyldimethoxybenziporphyrins. These dimethoxyporphyrinoids exhibited weakly diatropic properties that were enhanced upon protonation.