Synthesis of 4-Alkylated 1,4-Dihydropyridines: Fe(II)-Mediated Oxidative Cascade Cyclization Reaction of Cyclic Ethers with Enaminones.

Syntheses of highly functionalized 4-alkylated 1,4-dihydropyridines (1,4-DHPs) from cyclic ethers and enaminones via iron(II)-mediated oxidative free radical cascade C(sp3)-H bond functionalization/C(sp3)-O bond cleavage/cyclization reaction have been first developed. This novel synthetic strategy offers an alternative method for the construction of 1,4-DHPs by using esters as the C4 sources, as well as expands the application of ethers in heterocycle synthesis.

Copper-Catalyzed Oxidative [1+2+1+2] Cascade Cyclization of N,N-Dimethyl Enaminones with Benzylamines: A Facile Access to Functionalized 1,4-Dihydropyridines.

Using benzylamines as the C4 source of 1,4-dihydropyridines (1,4-DHPs), a Cu-catalyzed oxidative [1+2+1+2] cascade cyclization for the synthesis of 1,4-DHPs was firstly developed. A broad range of easily available N,N-dimethyl enaminones and benzylamines are employed smoothly to provide a diverse range of 1,4-DHPs with high efficiency. This method is performed by a one-pot cascade C(sp3 )-H bond functionalization/C(sp3 )-N cleavage/cyclization strategy to form simultaneously two C(sp3 )-C(sp2 ) bonds, two C(sp2 )-N bonds, and a 1,4-DHP ring.

Transition-metal-free approach to quinolines via direct oxidative cyclocondensation reaction of N,N-dimethyl enaminones with o-aminobenzyl alcohols.

A transition-metal-free method for the construction of 3-substituted or 3,4-disubstituted quinolines from readily available N,N-dimethyl enaminones and o-aminobenzyl alcohols is reported. The direct oxidative cyclocondensation reaction tolerates broad functional groups, allowing the efficient synthesis of various quinolines in moderate to excellent yields. The reaction involves a C (sp3)-O bond cleavage and a C=N bind and a C=C bond formation during the oxidative cyclization process, and the mechanism was proposed.