A versatile aerobic catalytic system (I(2) and O(2)/TBHP) for C-H functionalization is reported. This CDC (cross-dehydrogentive coupling) reaction is compatible with a large number of nucleophiles and is performed under ambient reaction conditions. The scope of the metal-free CDC is illustrated by synthesizing a variety of functionalized tetrahydroisoquinolines and N,N-dimethylaniline. The highlight of the method is a Friedel-Crafts reaction of phenols and indole with tertiary amines.
An oxidative cross‐dehydrogenative coupling (CDC) reaction for the formation of CC and CP bonds is disclosed using a catalytic amount of DDQ (10 mol %) under aerobic conditions (see scheme). This unprecedented environmentally benign strategy of using AIBN (10 mol %) and molecular oxygen to regenerate DDQ exhibits a larger substrate scope. For the first time, an efficient utility of 4‐hydroxycoumarins as pronucleophiles for CDC is presented.
The last two decades have witnessed the emergence of direct enolization protocols providing atom-economical and operationally simple methods to use enolates for stereoselective C-C bond-forming reactions, eliminating the inherent drawback of the preformation of enolates using stoichiometric amounts of reagents. In its infancy, direct enolization relied heavily on the intrinsic acidity of the latent enolates, and the reaction scope was limited to readily enolizable ketones and aldehydes. Recent advances in this field enabled the exploitation of carboxylic acid derivatives for direct enolization, offering expeditious access to synthetically versatile chiral building blocks. Despite the growing demand for enantioenriched fluorine-containing small molecules, α- and β-fluorinated carbonyl compounds have been neglected in direct enolization chemistry because of the competing and dominating defluorination pathway. Herein we present a comprehensive study on direct and highly stereoselective Mannich-type reactions of α- and β-fluorine-functionalized 7-azaindoline amides that rely on a soft Lewis acid/hard Brønsted base cooperative catalytic system to guarantee an efficient enolization while suppressing undesired defluorination. This protocol contributes to provide a series of fluorinated analogs of enantioenriched β-amino acids for medicinal chemistry.
A solvent-free synthesis of α-aminonitriles and β-nitroamines by oxidative cross-dehydrogenative coupling under aerobic condition is reported. A catalytic amount of molybdenum(vi) acetylacetonoate was found to catalyze cyanation of tertiary amines to form α-aminonitriles, whereas vanadium pentoxide was found to promote aza-Henry reaction to furnish β-nitroamines. Both of these environmentally benign reactions are performed in the absence of solvents using molecular oxygen as an oxidant.
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