novel semipinacol rearrangement using dibromocyclopropanes as sources of carbocations was developed. Heating dibromocyclopropanes bearing a 1‐hydroxyalkyl group with silver perchlorate and 2,6‐lutidine induced cleavage of the cyclopropane ring to form allyl cations, which underwent 1,2‐shift of a substituent at the α‐position of the hydroxygroup to give β,γ‐unsaturated carbonylcompounds having a quaternary
Rhodium-Catalyzed Regio- and Enantioselective Allylic Amination of Racemic 1,2-Disubstituted Allylic Phosphates
作者:Wen-Bin Xu、Minghe Sun、Mouhai Shu、Changkun Li
DOI:10.1021/jacs.1c04016
日期:2021.6.9
Alkynylphosphines are rarely used as ligands in asymmetric metal catalysis. We synthesized a series of chiral bis(oxazoline)alkynylphosphine ligands and used them in Rh-catalyzed highlyregio- and enantioselectiveallylicamination reactions of 1,2-disubstituted allylic phosphates. Chiral 1,2-disubstituted allylic amines were synthesized in up to 95% yield with >20:1 branched/linear (b/l) ratio and
Toward General Access to the <i>Aspidosperma</i>-Type Terpenoid Indole Alkaloids: Synthesis of the Key 3,3-Disubstituted Piperidones through Enantioselective Intramolecular Heck-Type Reaction of Chloroformamides
An enantioselective intramolecular Heck-type reaction of chloroformamides has been developed for the synthesis of 3,3-disubstituted piperidones. The desired piperidone was formed in the presence of a palladium catalyst, an optically active phosphoramidite ligand, K3PO4 and Ag3PO4. The obtained piperidone was converted to epieburnamonine.
Total Synthesis of (±)-Rhazinal Using Novel Palladium-Catalyzed Cyclizations
作者:Alfred L. Bowie、Dirk Trauner
DOI:10.1021/jo801791j
日期:2009.2.20
A concise synthesis of (±)-rhazinal that hinges on novel oxidative Heck cyclizations and palladium-catalyzed direct couplings is described. An X-ray structure of N-MOM-rhazinal, which provides insight into the conformation of the strained 9-membered lactam ring, is described.
The rare chemoselectivity between two different aryl halides was realized by optimizing the kinetics of the different steps of this multicomponent process. The new developed method led to the rapidsynthesis of rhazinal in a highly efficient manner.