Directed Metal (Oxo) Aliphatic C–H Hydroxylations: Overriding Substrate Bias
摘要:
The first general strategy for a directing effect on metal (oxo)-promoted C-H hydroxylations is described. Carboxylic acid moieties on the substrate overcome unfavorable electronic, steric, and stereoelectronic biases in C-H hydroxylations catalyzed by the non-heme iron complex Fe(PDP). In a demonstration of the power of this directing effect, C-H oxidation is diverted away from an electronically favored C-1 H abstraction/rearrangement pathway in the paclitaxel framework to enable installation of C-2 oxidation in the naturally occurring oxidation state and stereoconfiguration.
A photocatalyzed oxidation of functionalized cyclobutanones to access γ-lactones has been performed in acetonitrile at room temperature, using 9,10-anthraquinone as catalysts in the presence of TFA. The process furnish good to excellent yields of the desired compounds in 4–16 h reaction and after simple filtration of the recyclable catalyst.