Radical transformations for allene synthesis

Abstract

Allenes are valuable organic molecules that feature unique physical and chemical properties. They are not only often found in natural products, but also act as versatile building blocks for the...

Access to functionalized alkynylcyclopropanes via reductive radical-polar crossover-based reactions of 1,3-enynes with alkyl radicals

“…With a radical addition/SET reduction/allenylation cascade as the strategy, we successfully developed some useful and practical protocols dealing with modular access to functionalized allenes. 9,10 Inspired by the easy preparation of cyclopropanes via the RPC process, we wondered whether cyclopropanation of 1,3-enynes would take place ahead of the allenylation reaction (Scheme 3). Notably, functionalized alkynylcyclopropanes bearing both a triple bond and one or more functional groups at the three-membered ring are an especially attractive type of cyclopropane molecule.…”

Alkoxyl Radical-Mediated Ring Expansion/1,4-Difunctionalization of 1,3-Enynes upon Copper Catalysis

“…Owing to the unique structural characteristics, properties, and versatile chemical reactivities, allenes are important structural motifs that are frequently found in natural products, pharmaceuticals, and organic synthons (Scheme a) . Therefore, the synthesis of allenes has attracted sustained attention from chemists . Among the established methods, 1,4-difunctionalization of 1,3-enynes has become a step and atom economy strategy to access those compounds from simple materials .…”

Diversified access to di- and trisubstituted allenes via nickel-catalysed reactions of 1,3-enynes with alkyl N-hydroxyphthalimide esters

“…8 Employing an allenyl radical as the proposed intermediate, many elegant protocols describing the difunctionalization of 1,3-enynes with radicals have been successfully developed for the preparation of allenes. 9 Surprisingly, the preparation of 1,1-disubstituted allenes based on the functionalization of 1,3-enynes is still untouched. In addition to polar and radical pathways, a reductive radical-polar crossover process was employed by us as a useful complementary route for the synthesis of functionalized 1,2-allenyl ketones 10 enabled by photoredox 5 a or nickel catalysis.…”