A Novel Allyl Transfer Coupled with a Grob Fragmentation

Abstract

A novel acid-promoted rearrangement is disclosed. In the previously unknown transformation, an allyl group migrated to an in situ formed carbocation stabilized by an electron-rich aryl or heteroaryl group, resulting in a stereoselective intramolecular Grob fragmentation. The outcome of the rearrangement observed with an array of substrates can be satisfactorily rationalized using a working hypothesis with the aid of a six-membered transition state similar to those proposed for the anionic oxy-Cope or oxonia-Cope rearrangements, but involving only one instead of two double bonds.

Stereoselective Visible‐Light Catalyzed Cyclization of Bis(enones): A Viable Approach to the Synthesis of Enantiomerically Enriched Cyclopentane Rings

“…The removal of the chiral auxiliary was realized by reaction with sodium methoxide in methanol, [11] to give in quantitative yield the enantiomerically enriched cyclopentane 9 . The enantiomeric excess was evaluated by HPLC analysis on chiral stationary phase and confirmed the diastereoisomeric ratio evaluated by NMR on purified products 8 a – e .…”

Furan Oxidation Strategy for the Synthesis of the Macrolactone Analogue of Migrastatin

“…Protection of the hydroxy group in 9 as its TBDMS ether furnished the silyl ether 10 in 93% yield. Reductive cleavage of the thiazolidine auxiliary with DIBAL-H gave the known aldehyde 11 in 86% yield. The aldehyde 11 on treatment with Ando’s phosphonate 12 furnished the Z -unsaturated ester 7 in 83% yield as a single diastereomer .…”