An efficient and recyclable hybrid nanocatalyst to promote enantioselective radical cascade rearrangements of enediynes.

Mesoporous silica grafted with a tertiary amine was used as a basic nanocatalyst to promote in confined medium the enantioselective cascade rearrangement of enediynes based on the phenomenon of memory of chirality; the multi-substrates recyclable catalytic reagent could easily be recovered by simple filtration, and reused without any decrease in activity even when changing the solvent.

Memory of chirality in cascade rearrangements of enediynes.

The cascade rearrangement of chiral enediynes 1c-e, involving successively 1,3-proton shift, Saito-Myers cyclization, 1,5-hydrogen atom transfer, and intramolecular coupling of the resulting biradical, proceeded at 80 °C to form tri- and tetracyclic heterocycles possessing a quaternary stereogenic center with a very high level of memory of chirality.

A flexible, stereoselective dimethylzinc-mediated radical-anionic cascade: dramatic influence of additional Lewis acids.

Dimethylzinc-mediated addition of acyloxymethyl radicals to diethyl fumarate led to the highly stereoselective formation of disubstituted gamma-lactones in mean to good yields; this cascade provides a new example of a one-pot process mediated by dimethylzinc involving a tandem radical-anionic reaction; the chemoselectivity of the reaction was totally modified by additional Lewis acids.