Metal-Catalyst-Free Radical Cyclization of 1,6-Enynes for the Selective and Switchable Synthesis of Lactams in Water

Abstract

Three types of novel radical cyclization of 1,6-enynes with sulfonyl hydrazides have been presented, which provided convenient synthetic approaches for accessing five-membered cyclic lactams, five-membered cyclic lactams containing C–I bond, and six-membered cyclic lactams. Notably, these transformations are implemented in metal-catalyst-free systems, in which three classes of important lactam derivatives were synthesized with selectivity and controllability from the same substrate using water as the green solvent.

Photoinduced Radical Cyclization of 1,6‐Diynes: Rapid Access to Highly Substituted Carbocyclic and Heterocyclic Compounds

“…Based on the above control experiments, data from the literature, [3f,4f,15–16] and our previous work, [12] we suggest a plausible reaction mechanism, as shown in Scheme 6. First, 4‐methylbenzenesulfonyliodide ( 2 a ) absorbs blue LED light to produce sulfonyl ( 2 a’ ) and iodine ( 2 a” ) radicals via homolytic bond fission [12b,c] .…”

Difunctionalization of Dienes, Enynes and Related Compounds via Sequential Radical Addition and Cyclization Reactions

“…In 2022, Li and coworkers reported a reaction of 1,6-enynyl amides for the synthesis of γ -lactams. The reaction of 1,6-enynyl amides and sulfonyl hydrazides in H 2 O at 70 °C for 20 h in the presence of TBHP gave product 36 in moderate-to-good yields ( Scheme 35 ) [ 49 ]. The reaction mechanism suggests that PhSO 2 radical, generated from the reaction of PhSO 2 NHNH 2 with TBHP and TBAI, adds to the C=C double bond of amide followed by 5- exo cyclization and coupling with iodine radical to give product 36a .…”

Biocatalytic stereoselective synthesis of pyrrolidine-2,3-diones containing all-carbon quaternary stereocenters

“…[10][11][12][13] The combination of these heterocycles with quaternary stereocenters is particularly highly regarded due to their presence in many alkaloids. [14][15][16][17][18][19] The crinane alkaloid family, which belongs to the Amaryllidaceae alkaloids, represents such scaffolds that contain catechol-based substituted five-membered nitrogen heterocycles with all-carbon quaternary stereocenters. 20 These alkaloids possess biological activities against malaria, Alzheimer's disease, viral infections, inflammation, and cancers [21][22][23][24][25][26] (Fig.…”