Journal of Organic Chemistry最新文献

Here, we revealed a convenient synthetic protocol for unique pyrido[2,3-c]pyridazine and pyrido[3,2-e][1,2]oxazine scaffolds with excellent regioselectvity and diastereoselectivity. The functionalized pyrido[2,3-c] pyridazines were successfully synthesized via a Cs₂CO₃-promoted [4 + 2] cycloaddition reaction of α-halogenated N-tosylhydrazones or N-acylhydrazones and 5,6-unsubstituted 1,4-dihydropyridines under mild conditions. Additionally, the similar base-promoted [4 + 2] cycloaddition reaction of α-chlorogenated oximes and 5,6-unsubstituted 1,4-dihydropyridines afforded functionalized pyrido[3,2-e][1,2]oxazines in satisfactory yields. The features of this reaction included mild reaction conditions, broad substrate scopes, high functional group tolerance, and significant atomic economy.

A class of prearomatic carboxylic acid p-quinol ester radical precursors has been developed successfully, which could undergo homolytic cleavage of the para C-O bond of p-quinol esters via pyridine-boryl radical-induced aromatization in the presence of pyridines and diboron reagents, affording the corresponding alkyl radical via decarboxylation from the carboxyl radical in situ. In addition, the prearomatic radical precursors were further applied in radical substitution with phenylsulfonyl compounds and radical self-coulpings. This method not only provides a new approach to the generation of a radical intermediate but also expands the application of boron radicals.

A 1,8-diazabicyclo[5.4.0]undecane-7-ene (DBU)-mediated hydroalkylation of enamides with malonic acid diesters/β-carbonyl esters has been established, featuring no metal involvement, mild reaction conditions, and good functional group tolerance. The protocol enables the expedited preparation of a variety of β-amino esters. Preliminary mechanistic investigations, encompassing control experiments and capture experiments of key intermediates, have substantiated the proposed DBU-mediated hydroalkylation pathway.

A new class of chiral bifunctional imidazole catalysts has been designed and synthesized, utilizing economical amino alcohols as precursors, significantly expanding the diversity of N-1 position catalysts. These catalysts exhibit excellent substrate activation and stereoselectivity control and have been successfully employed in the asymmetric acylation of 5-hydroxy-furanones/3-hydroxy-phthalides through dynamic kinetic resolution, producing a series of chiral furanone and phthalide analogues featuring a quaternary stereocenter. This asymmetric acylation reaction exhibits excellent reactivity and enantioselectivity, has a wide range of applicability, requires a low catalyst loading, and can be readily converted into valuable building blocks. Moreover, DFT calculations revealed the detailed reaction mechanism and demonstrated that the weak N–H···O and C–H···O interactions between the catalyst and substrate are the key factors affecting the stereoselectivity.

Herein, we report sodium iodide (NaI)-catalyzed decarboxylative C-H alkylation of azauracils with N-hydroxyphthalimide (NHPI) esters facilitated by visible light activation of catalytic electron donor-acceptor (EDA) complexes. Control experiments and density functional theory calculations suggest that the decarboxylative coupling reaction proceeds via a transiently assembled EDA complex between the NHPI ester and NaI in N,N-dimethylacetamide solvent. This synthetic method efficiently applies to primary, secondary, and tertiary NHPI esters under mild, photocatalyst-free, and redox-neutral conditions, achieving high yields of the desired alkylated azauracils.