Synthesis of Methylenebicyclo[3.2.1]octanol by a Sm(II)-Induced 1,2-Rearrangement Reaction with Ring Expansion of Methylenebicyclo[4.2.0]octanone

Abstract

Direct conversion of methylenebicyclo[4.2.0]octanone to methylenebicyclo[3.2.1]octanol by a Sm(II)-induced 1,2-rearrangement with ring expansion of the methylenecyclobutane is described. Three conditions were optimized to allow the adaptation of this approach to various substrates. A rearrangement mechanism is proposed involving the generation of a ketyl radical and cyclopentanation by ketyl-olefin cyclization, followed by radical fragmentation and subsequent protonation.

Metagenomic ene-reductases for the bioreduction of sterically challenging enones

“…Finally, taking advantage of the metagenomic enzyme to tolerate higher concentrations of DMSO, a bulkier tricyclic enone rac -16 was also synthesized. 35 Remarkably it was also accepted to give the reduced product rac -17 in 50% yield. This suggests that the presence of the aromatic ring may enable both faces of the C C bond in 16 to be presented to the FMN co-factor.…”

Total Synthesis of (±)-Jujuyane

“…Dissolving metal reduction and SmI 2 reduction, which have many precedents in opening of the ether bridge in seven-membered ring compounds from oxidopyrylium cycloadducts, afforded undesirable results. Simple reduction of the carbonyl group occurred in the case of dissolving metal reduction, and an unanticipated migration of the vinyl group was observed under SmI 2 reduction conditions (Scheme ). Unlike the seven-membered ring systems, the ketyl generated in intermediate 19 appeared to have poor orbital overlap with the σ* C–O orbital for cleavage of the ether bridge.…”

Au-Catalyzed Asymmetric Polyene Cyclization and Its Application in the Total Synthesis of (+)-2-Ketoferruginol, (+)-Fleuryinol B, (+)-Salviol, and (−)-Erythroxylisin A

“…Under the irradiation of a 450 W high-pressure mercury lamp, a [2 + 2] photocycloaddition between enone 9 and allene took place smoothly to form the ketone 10 in 50% yield . Uneventfully, a SmI 2 -induced 1,2- rearrangement/ring expansion of ketone 10 followed by a Dess–Martin periodinane oxidation completed the first catalytic asymmetric total synthesis of (−)-erythroxylisin A (89% ee), whose spectroscopic data matched well with the reported ones.…”