Hong-Wu Zhao

[3 + 2] Cycloaddition of Oxazol-5-(4H)-ones with Nitrones for Diastereoselective Synthesis of Isoxazolidin-5-ones

In the presence of TMSCl, the [3 + 2] cycloaddition of oxazol-5-(4H)-ones with nitrones proceeded smoothly and furnished the desired isoxazolidin-5-ones with high diastereoselectivities in reasonable chemical yields. The chemical structure of the title compounds was firmly confirmed by X-ray single-crystal structure analysis.

Facile access to novel 1,2,4-oxadiazinan-5-ones via [3 + 3] cycloaddition of in situ generated azaoxyallyl cations with nitrones

In the presence of Na2CO3, azaoxyallyl cations in situ generated from α-halohydroxamates with nitrones readily underwent [3 + 3] cycloaddition, and gave rise to 1,2,4-oxadiazinan-5-one derivatives in 56–99% chemical yields. The chemical structure of the title compounds was unambiguously identified by X-ray single crystal structure analysis.

Direct access to non-aromatic 1,2,3,6-tetrahydro-1,2,3,4-tetrazines via [4 + 2] cycloaddition of α-halogeno hydrazones with azodicarboxylic acid derivatives

In the presence of K2CO3, the [4 + 2] cycloaddition of α-halogeno hydrazones with azodicarboxylic acid derivatives proceeded efficiently, and delivered novel non-aromatic 1,2,3,6-tetrahydro-1,2,3,4-tetrazines in moderate to excellent chemical yields.

Highly diastereoselective synthesis of imidazolidine-dispirooxindoles via three-component [3 + 2] cycloadditions of isatins, 2-(aminomethyl)pyridine and isatin-based imines

In the presence of Et3N, the [3 + 2] cycloaddition of isatins, 2-(aminomethyl)pyridine and isatin-based imines proceeded readily, and furnished novel imidazolidine-dispirooxindoles in up to 84% yield with up to >99:1 diastereoselectivity. The relative configuration of the imidazolidine-dispirooxindoles was firmly confirmed on the basis of X-ray single crystal structure analysis. The reaction mechanism was assumed to account for the diastereoselective formation of the imidazolidine-dispirooxindoles.

Facile construction of novel imidazolidine-spirooxindoles via diastereoselective cycloaddition of N-acylhydrazine-derived imines with 3-isothiocyanato oxindoles

In the presence of 10 mol% of Na2CO3, the desired imidazolidine-spirooxindoles were obtained in 81–99% yield with up to 99 : 1 dr by means of the diastereoselective [3 + 2] cycloaddition of N-acylhydrazine-derived imines with 3-isothiocyanato oxindoles. Single-crystal X-ray structure analysis was conducted to determine the relative stereochemistry of the imidazolidine-spirooxindoles. Diastereoselective access to the imidazolidine-spirooxindoles was hypothesized by the proposed mechanism.

1,3-Dipolar [3 + 3] cycloaddition of α-halohydroxamate-based azaoxyallyl cations with hydrazonoyl chloride-derived nitrile imines

Promoted by Et3N, the 1,3-dipolar [3 + 3] cycloaddition of α-halohydroxamate-based azaoxyallylcations with hydrazonoyl chloride-derived nitrile imines occurred efficiently, and furnished desired products in acceptable chemical yields. The chemical structure of the title compounds was firmly confirmed by an X-ray single crystal structure analysis.

Construction of 2,3,4,5-tetrahydro-1,2,4-triazines via [4 + 2] cycloaddition of α-halogeno hydrazones to imines

In the presence of sodium carbonate, the [4 + 2] cycloaddition of α-halogeno hydrazones to imines proceeded readily, and furnished 2,3,4,5-tetrahydro-1,2,4-triazines in moderate to high chemical yields.

Diastereoselective Synthesis of Rotationally Restricted Chiral Phenylpyridines via Intramolecular Cascade Cyclization of N-Acyliminium Ions Containing α-Amino Acid Residues

Abstract A series of chiral phenylpyridines possessing a fused chiral bridge were synthesized diastereoselectively via cascade cyclizations, where N-acyliminium ions including an enantiopure α-amino acid residue were involved. The absolute configuration of the synthesized phenylpyridines was identified unambiguously by using nuclear Overhauser effect difference and circular dichroism (CD) measurements on the basis of literature methods. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.] GRAPHICAL ABSTRACT

Synthesis of a Series of Novel Chiral Aromatic Heterocyclic Macrocycles Containing L-Amino Acid and 2,5-Bisphenyl-1,3,4-triazole Subunits

Abstract An array of novel chiral aromatic heterocyclic macrocycles, which may show potential enantiomeric recognition to variable D- and L-amino acids, were synthesized in acceptable yield. The desired macrocycles 3a–c and 4a–c were obtained via the condensation reaction of chiral diamine intermediates 2a–c with 2,5-bis(o-chloroformylphenyl)-1,3,4-triazole 5 in a presence of Et3N in a highly diluted dichloromethane solution at room temperature.

Diastereoselective and Enantioselective Synthesis of Barbiturate-Fused Spirotetrahydroquinolines via Chiral Palladium(0)/Ligand Complex Catalyzed [4 + 2] Cycloaddition of Vinyl Benzoxazinanones with Barbiturate-Based Olefins

Under the catalysis of chiral palladium(0)/ligand complex, the [4 + 2] cycloaddition between vinyl benzoxazinanones and barbiturate-based olefins proceeded readily and provided barbiturate-fused spirotetrahydroquinolines in up to 96% chemical yield with up to >99:1 dr and 97% ee. The absolute configuration of barbiturate-fused spirotetrahydroquinolines was clearly identified by X-ray single crystal structure analysis. The reaction mechanism was proposed to shed light on the enantioselective formation of barbiturate-fused spirotetrahydroquinolines.