Sulfonyl radical triggered selective iodosulfonylation and bicyclization of 1,6-dienes

Abstract

A novel sulfonyl radical triggered selective iodosulfonylation and bicyclizations of 1,6-dienes has been described for the first time. High selectivity and efficiency, mild reaction conditions, excellent functional group compatibility, and...

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

“…The commonly used organic solvents are generally volatile and toxic, so it is a sustainable choice to find environmentally friendly media as an alternative. − As the greenest and safest solvent in nature, water has drawn the attention of chemists due to its excellent biocompatibility, nonflammability, and nontoxicity. − Hence, it is of great significance to exploit organic reactions in aqueous media. In addition, the development of the metal-catalyst-free method is also booming due to its low toxicity, long service life, and simple postprocessing. − Inspired by these advances and as a continuation of our efforts in radical cyclization of unsaturated hydrocarbons, − we present a sustainable and switchable radical cyclization of 1, n -enynes with sulfonyl hydrazines in aqueous media without a metal catalyst to form five-membered cyclic lactams, five-membered cyclic lactams containing C–I bond, and six-membered cyclic lactams (Scheme -2). These protocols have the following prominent advantages: (1) water as the solvent; (2) metal-catalyst-free; (3) high selectivity and controllability; and (4) preparation of diversified products from the same substrate.…”

Radical annulation using a radical reagent as a two-carbon unit

“…13 The method for the insertion of SO 2 is environmentally friendly and efficient compared to the conventional method for obtaining sulfonyl radicals. 6–8 Mechanistic studies show that the aryldiazonium tetrafluoroborate reacts with DABCO·(SO 2 ) 2 to form intermediate I , then both SO 2 and the aryl radical are produced by I and they combine to form the aryl sulfonyl radical and subsequently form the final product through a process similar to that reported previously. 6…”

“…Different from the previous strategies, 6,7 the authors utilized 1,6-dienes as the radical acceptor by the use of Cu(OAc) 2 as a catalyst and TBHP as an oxidant (Scheme 2). 8 Simultaneously, mechanistic studies indicate that the sulfonyl radical E is formed in the Cu(OAc) 2 /TBHP system. Then, the radical intermediate F is generated by sequential intermolecular radical addition and intramolecular cyclization.…”

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

“…Li and Wei, in 2021, reported a Cu-catalyzed radical reaction of 1,6-dienyl amides for the synthesis of substituted γ -lactams. The reaction of 1,6-dienyl amides and RSO 2 NHNH 2 in CH 3 CN in the presence of CuI and TBHP gave product 38 in moderate-to-good yields ( Scheme 37 ) [ 51 ]. The reaction mechanism suggests that the sulfonyl radical, generated from the reaction of RSO 2 NHNH 2 with TBHP, adds to the C=C double bond of amide followed by 5- exo cyclization, oxidation to carbocation, and trapping I − anion of CuI to provide iodosulfonylation of product 38a .…”