Modular Synthesis of Alkenyl Sulfamates and ß-Ketosulfonamides via Sulfur(VI) Fluoride Exchange (SuFEx) Click Chemistry and Photomediated 1,3-Rearrangement.

Herein, we report a synthesis of medicinally relevant ß-ketosulfonamides via a photomediated 1,3-rearrangement of alkenyl sulfamates. This protocol tolerates a wide array of sensitive functional groups including alkenes, alkynes, and nitrogen-based heterocycles. Additionally, this work provides a general approach toward alkenyl sulfamates via a two-step Sulfur(VI) Fluoride Exchange (SuFEx) sequence capitalizing on SO2F2 as a linchpin to efficiently couple readily available ketones and amines without a large excess of either partner.

Direct C-H α-Arylation of Enones with ArI(O2CR)2 Reagents.

α-Arylation of α,ß-unsaturated ketones constitutes a powerful synthetic transformation. It is most commonly achieved via cross-coupling of α-haloenones, but this stepwise strategy requires prefunctionalized substrates and expensive catalysts. Direct enone C-H α-arylation would offer an atom- and step-economical alternative, but such reports are scarce. Herein we report the metal-free direct C-H arylation of enones mediated by hypervalent iodine reagents. The reaction proceeds via a reductive iodonium Claisen rearrangement of in situ-generated ß-pyridinium silyl enol ethers. The aryl groups are derived from ArI(O2CCF3)2 reagents, which are readily accessed from the parent iodoarenes. The reaction is tolerant of a wide range of substitution patterns, and the incorporated arenes maintain the valuable iodine functional handle. Mechanistic investigations implicate arylation via an umpoled "enolonium" species and show that the presence of a ß-pyridinium moiety is critical for the desired C-C bond formation.

Hypervalent Iodine Reagents in High Valent Transition Metal Chemistry.

Over the last 20 years, high valent metal complexes have evolved from mere curiosities to being at the forefront of modern catalytic method development. This approach has enabled transformations complimentary to those possible via traditional manifolds, most prominently carbon-heteroatom bond formation. Key to the advancement of this chemistry has been the identification of oxidants that are capable of accessing these high oxidation state complexes. The oxidant has to be both powerful enough to achieve the desired oxidation as well as provide heteroatom ligands for transfer to the metal center; these heteroatoms are often subsequently transferred to the substrate via reductive elimination. Herein we will review the central role that hypervalent iodine reagents have played in this aspect, providing an ideal balance of versatile reactivity, heteroatom ligands, and mild reaction conditions. Furthermore, these reagents are environmentally benign, non-toxic, and relatively inexpensive compared to other inorganic oxidants. We will cover advancements in both catalysis and high valent complex isolation with a key focus on the subtle effects that oxidant choice can have on reaction outcome, as well as limitations of current reagents.