Highly regioselective photodimerization of 1,4-dihydropyridines: An efficient synthesis of novel 3,6-diazatetraasteranes

Visible-Light-Mediated Catalyst-Free [2+2] Cycloaddition Reaction for Dihydrocyclobuta[b]naphthalene-3,8-diones Synthesis under Mild Conditions

A facile and efficient visible-light-mediated method for directly converting 1,4-naphthoquinones into dihydrocyclo-buta[b]naphthalene-3,8-diones (DHCBNDOs) under mild and clean conditions without using any photocatalysts is reported. This approach exhibited favorable compatibility with functional groups and afforded a series of DHCBNDOs with excellent regioselectivity and high yields. Moreover, detailed mechanism studies were carried out both experimentally and theoretically. The readily accessible, low-cost and ecofriendly nature of the developed strategy will endow it with attractive applications in organic and medicinal chemistry.

Construction of 3,12-Diazatetracyclododecane-dienes through Unexpected Visible-Light-Induced Radical Cascade Cyclization

A novel visible-light-induced cascade radical cyclization reaction of 3-cyano-4-aryl-1,4-dihydropyridines for the construction of 3,12-diazatetracyclododecane-diene derivatives is reported for the first time. In the presence of 410 nm blue LED lamp as the light source and ethanol as the solvent, the reactions proceed smoothly to afford photocyclization products in good yields. The process is carried out through the breaking of original C═C double bonds and the formation of three new single bonds in one pot and proved to be able to tolerate different substituents.

A four-component domino reaction for the synthesis of novel bridgehead nitrogen-containing pyrido[1,2-d][1,4]diazepines

An efficient methodology for the synthesis of a new family of novel bridgehead nitrogen-containing pyrido[1,2-d][1,4]diazepines has been described and its mechanism has been proposed, which follows a ring-closure and ring-cleavage pathway.

Catalytic Asymmetric [3 + 2] Annulation of Hantzsch Esters with Racemic N-Sulfonylaziridines

Hantzsch esters (HEs) served as two-carbon partners in a copper(I)-catalyzed enantioselective [3 + 2] annulation with racemic 2-(hetero)aryl-N-sulfonyl aziridines via kinetic resolution to provide pyrrolo[2,3-b]tetrahydropyridines containing multiple contiguous stereogenic centers including all-carbon quaternary centers in excellent yields and enantiopurities and moderate-to-excellent diastereoselectivities. Mainly dependent upon the structures of the aziridines, a competitive hydrogenolysis process with HEs as the hydrogen source was also observed in some cases.

Studies on chemoselective synthesis of 1,4- and 1,2-dihydropyridine derivatives by a Hantzsch-like reaction: a combined experimental and DFT study

In the experimental process of preparing diethyl 3,5-dicarboxylate-1,4-dihydropyridine (1,4-DHP) by a Hantzsch-like reaction, it was found that a by-product named diethyl 3,5-dicarboxylate-1,2-dihydropyridine (1,2-DHP) was produced in the reaction. To discuss this phenomenon, the effects of the reaction conditions on the yield ratio of 1,4-DHP and 1,2-DHP were studied by using aromatic amines, aromatic aldehydes and ethyl propiolate as raw materials. The mechanisms for the formation of 1,4-DHP and 1,2-DHP were proposed based on the isolated intermediate named diethyl 4-((phenylamino)methylene)pent-2-enedioate generated by the Michael addition of aniline and ethyl propiolate. The transition state structures were optimized and the reaction energy barriers of intermediates in the speculated mechanisms were calculated by DFT calculations at the M062X/def2TZVP//B3LYP-D3/def-SVP level. It was found that the reaction energy barriers and dominant configurations of intermediates IM2 and IM3' are the determinants for the chemoselectivity. Together, these results demonstrate a high chemoselectivity in the synthesis of 1,4-DHPs and 1,2-DHPs by a Hantzsch-like reaction and that 1,4-DHPs and 1,2-DHPs can be easily obtained under different conditions.

Hetero-intermolecular [2+2] photocycloaddition of 1,4-dihydropyridines: a combined experimental and DFT study

A detailed DFT mechanistic study of hetero-intermolecular [2+2] photocycloaddition of 1,4-DHPs was carried out for investigating the regioselectivity of such transformation.