Catalyst-controlled aliphatic C-H oxidations with a predictive model for site-selectivity.

Selective aliphatic C-H bond oxidations may have a profound impact on synthesis because these bonds exist across all classes of organic molecules. Central to this goal are catalysts with broad substrate scope (small-molecule-like) that predictably enhance or overturn the substrate's inherent reactivity preference for oxidation (enzyme-like). We report a simple small-molecule, non-heme iron catalyst that achieves predictable catalyst-controlled site-selectivity in preparative yields over a range of topologically diverse substrates. A catalyst reactivity model quantitatively correlates the innate physical properties of the substrate to the site-selectivities observed as a function of the catalyst.

Oxidative Heck vinylation for the synthesis of complex dienes and polyenes.

We introduce an oxidative Heck reaction for selective complex diene and polyene formation. The reaction proceeds via oxidative Pd(II)/sulfoxide catalysis that retards palladium-hydride isomerizations which previously limited the Heck manifold's capacity for furnishing stereodefined conjugated dienes. Limiting quantities of nonactivated terminal olefins (1 equiv) and slight excesses of vinyl boronic esters (1.5 equiv) that feature diverse functionality can be used to furnish complex dienes and polyenes in good yields and excellent selectivities (generally E:Z = >20:1; internal:terminal = >20:1). Because this reaction only requires prior activation of a single vinylic carbon, improvements in efficiency are observed for synthetic sequences relative to ones featuring reactions that require activation of both coupling partners.

Synthetic versatility in C-H oxidation: a rapid approach to differentiated diols and pyrans from simple olefins.

Conventionally, C-H oxidation reactions are used to install functional groups. The use of C-H oxidation to transform simple starting materials into highly versatile intermediates, which enable rapid access to a range of complex target structures, is a new area with tremendous potential in synthesis. Herein we report a Pd(II)/sulfoxide-catalyzed allylic C-H oxidation to form anti-1,4-dioxan-2-ones from homoallylic oxygenates. These versatile building blocks are rapidly elaborated to differentiated syn-1,2-diols, stereodefined amino-polyols, and syn-pyrans, structures ubiquitous in medicinally important complex molecules found in Nature. We also demonstrate that a C-H oxidation approach to the synthesis of these motifs is orthogonal and complementary to other state-of-the-art methods.

Cross-coupling of cyclopropyl- and cyclobutyltrifluoroborates with aryl and heteroaryl chlorides.

Suitable conditions were found for the Suzuki-Miyaura cross-coupling reaction of potassium cyclopropyl- and cyclobutyltrifluoroborates with aryl chlorides. Both of these secondary alkyl trifluoroborates coupled in moderate to excellent yield with electron-rich, electron-poor, and hindered aryl chlorides to give a variety of substituted aryl cyclopropanes and cyclobutanes.

Scope of aminomethylations via Suzuki-Miyaura cross-coupling of organotrifluoroborates.

We previously reported the Suzuki-Miyaura reaction of N,N-dialkylaminomethyltrifluoroborates with aryl bromides. Herein, we report a further investigation of the scope and limitations of this palladium-catalyzed aminomethylation reaction. Aryl chlorides, iodides, and triflates coupled in good to excellent yields to give N,N-dialkylbenzylic amines. The aminomethylation of alkenyl bromides was also examined.