Diastereoselective Formation of Quaternary Stereocenters in Imidazole N-Oxide Cycloaddition with Fluoroalkenes

Imidazole N-oxides are attractive starting materials for the preparation of complex molecules containing an imidazole ring. Dipolar cycloaddition between 1,1-difluoroalkenes and imidazole N-oxides bearing a chiral auxiliary performed in the presence of oxygen or nitrogen nucleophiles was found to provide access to esters and amides bearing a 2-azaheteroaryl substituent at the α position of the imidazole ring as mixtures of diastereomers that, in most cases, are readily separable. This three-component reaction introduces a new tertiary or quaternary all-carbon stereocenter into the heterocyclic ring at a position originally occupied by hydrogen. Importantly, products containing a trifluoromethyl group attached to this stereocenter are readily available as well.

An I(I)/I(III) Catalysis Route to the Heptafluoroisopropyl Group: A Privileged Module in Contemporary Agrochemistry

The heptafluoroisopropyl group is emerging as a privileged chemotype in contemporary agrochemistry and features prominently in the current portfolio of leading insecticides. To reconcile the expansive potential of this module with the synthetic challenges associated with preparing crowded, fluorinated motifs, I(I)/I(III) catalysis has been leveraged. Predicated on in situ generation of p-TolIF2, this route enables the direct difluorination of α-trifluoromethyl-β-difluorostyrenes in a single operation. This formal addition of fluorine across the alkene π-bond is efficient (up to 91% yield) and is compatible with a broad range of functional groups. The ArCF(CF3)2 moiety is conformationally preorganised, with the C(sp3)–F bond coplanar to the framework of the aryl ring, thereby minimising 1,3-allylic strain. Moreover, orthogonal multipolar C–F···C=O interactions have been identified in a phthalimide derivative. It is envisaged that this programmed vicinal difluorination enabled by a hypervalent iodine species will find application in functional molecule design in a broader sense.

A novel approach to bis(1,3-azol-2-yl)acetonitriles and bis(1,3-azol-2-yl)methanes via the [3 + 2]-dipolar cycloaddition of imidazole N-oxides and 2-heteroaryl-3,3-dimethylacrylonitriles

A new synthetic approach for obtaining previously unknown bis(1,3-azol-2-yl)acetonitriles and bis(1,3-azol-2-yl)methanes has been developed. It is based on 1,3-dipolar cycloaddition between 2-unsubstituted imidazole N-oxides and 2-(1,3-azol-2-yl)-3,3-dimethylacrylonitriles, which are easily available through the condensation of (1,3-azol-2-yl)acetonitriles with acetone. The method allows for the construction of various unsymmetric derivatives based on imidazole, oxazole, thiazole, and 1,3,4-thiadiazole cyclic molecules. Its potential has been demonstrated via the synthesis of 24 diverse derivatives with yields of 29-92%. Bis(1,3-azol-2-yl)acetonitriles can be converted to the corresponding bis(1,3-azol-2-yl)methanes via simple acid hydrolysis followed by subsequent spontaneous decarboxylation at nearly quantitative yields.

Direct defluorinative amidation-hydrolysis reaction of gem-difluoroalkenes with N,N-dimethylformamide, and primary and secondary amines

A novel and efficient method for the synthesis of arylacetamides by the reactions of gem-difluoroalkenes with N,N-dialkylformamides, and primary and secondary amines with the assistance of KOtBu and water was developed.

Synthesis of 3-fluoroalkenyl-3-trifluoromethyl-2-oxindoles by the reaction of indoline-2,3-diones with difluoromethylene phosphabetaine

An unprecedent reaction of indoline-2,3-diones and (triphenylphosphonio)difluoroacetate (PDFA) afforded novel 3-fluoroalkenyl-3-trifluoromethyl-2-oxindoles in moderate to excellent yields. These products could be transformed into other trifluoromethylated oxindole derivatives.