Synthesis of Oxazolidin-4-ones: Domino O-Alkylation/Aza-Michael/Intramolecular Retro-Claisen Condensation

Pd-Catalyzed Selective Arylative Cascade Cyclization of 1,6-Diynes and Dibenzoxaborins for Fused Naphthalene Derivatives

A palladium-catalyzed new mode of cascade arylative cyclization of 1,6-diynes is disclosed using dibenzoxaborin as an arylating agent featuring transmetalation and selective migratory insertion as the key steps. This process enables the efficient construction of polysubstituted fused naphthalene skeletons via the formation of three new C-C bonds through dual regioselectivity in both arylation as well as C-H functionalization. Some control experiments and kinetic isotope effect (KIE) studies were conducted to elucidate the reaction mechanism, and some product diversifications were achieved to showcase the synthetic potential.

Asymmetric Retro-Claisen Reaction Catalyzed by Chiral Aza-Bisoxazoline-Zn(II) Complex: Enantioselective Synthesis of α-Arylated Ketones

An asymmetric retro-Claisen reaction of α-monosubstituted β-diketones and quinones (or quinone imine) has been developed under the catalysis of a chiral aza-bisoxazoline-Zn(II) complex. The reaction proceeds via a sequence of conjugate addition, arylation, hemiketal anion-initiated C-C bond cleavage, and enantioselective protonation of enolate to provide various functionalized α-arylated ketones bearing a tertiary stereogenic center with high enantioselectivities. Notably, biologically important benzofuran and γ-butyrolactone derivatives could be synthesized by application of the developed protocol.

Copper-Catalyzed Three-Component Reactions of α-Ketoaldehyde, 1,3-Dicarbonyl Compound, and Organic Boronic Acid in Water: A Route to 1,4-Diketones

A novel three-component reaction of α-ketoaldehydes, 1,3-dicarbonyl compounds, and organic boronic acids catalyzed by CuO in water has been developed to give a wide range of products containing 1,3/1,4-diketones. The method has some advantages such as the use of readily available starting materials, wide substrate scopes, excellent yields, gram-scale synthesis, and mild reaction conditions.

The Fascinating Chemistry of α-Haloamides

The aim of this review is to highlight the rich chemistry of α-haloamides originally mainly used to discover new C-N, C-O and C-S bond forming reactions, and later widely employed in C-C cross-coupling reactions with C(sp3), C(sp2) and C(sp) coupling partners. Radical-mediated transformations of α-haloamides bearing a suitable located unsaturated bond has proven to be a straightforward alternative to access diverse cyclic compounds by means of either radical initiators, transition metal redox catalysis or visible light photoredox catalysis. On the other hand, cycloadditions with α-halohydroxamate-based azaoxyallyl cations have garnered significant attention. Moreover, in view of the important role in life and materials science of difluoroalkylated compounds, a wide range of catalysts has been developed for the efficient incorporation of difluoroacetamido moieties into activated as well as unactivated substrates.

(R,R/S,S)-9-Benzyl-3-methyl-7-phenyl-1,6-dioxa-3,9-diazaspiro[4.4]nonane-2,8-dione

The title compound, C19H18N2O4, a rare example of a spirocyclic orthoamide, was synthesized by a double cyclization of a N-Boc protected sarcosine derivative. The crystal structure of the racemic (R,R/S,S) modification reveals two near-orthogonal five-membered heterocyclic ring systems, each in an envelope configuration.

α-Halogenoacetamides: versatile and efficient tools for the synthesis of complex aza-heterocycles

This review presents the use of α-alkyl- and α-alkoxy-halogenoacetamides as powerful partners for domino and 1,3-dipolar cycloaddition reactions resulting in a ring closure.

Domino construction of a bullataketal core via double bond cleavage in activated dihydrofurans

A new rapid approach to structurally challenging and biologically relevant methanobenzodioxepines was developed via a Brønsted acid-triggered domino transformation of 3-carbonyl-4,5-dihydrofurans, substituted with MOM-protected o-hydroxyaryls at the C4 atom.

[3 + 2] Cycloaddition of aza-oxyallyl cations with aldehydes

We report here the [3 + 2] cycloaddition reactions of in situ-generated aza-oxyallyl cations with commercially available aldehydes.