RESUMEN
pivZPhos, as an effective ligand in the Cu-catalyzed asymmetric hydrogenation of ketones and aminoboration of alkenes, is prepared efficiently from the corresponding triflate of P-chiral dihydrobenzoazaphosphole 1. However, the previous approach to 1 by chiral separation is time-consuming and costly, preventing its production and further application on a large scale. In this report, a practical method for the large-scale preparation of 1 was developed via chiral chemical resolution with (1S,2S)-diaminocyclohexane as an effective resolution reagent.
Asunto(s)
Alquenos , Cetonas , Catálisis , Hidrogenación , EstereoisomerismoRESUMEN
The first rearrangement of 2-methyleneoxetanes to α,ß-unsaturated methylketones is reported. It is proposed that when these substrates are heated, the corresponding oxetenes are formed and subsequently undergo electrocyclic ring-opening to methyl vinylketones. In particular, α-silyl-α,ß-unsaturated methylketones were isolated in moderate to high yields and with high stereoselectivities. Based on the proposed mechanism, density functional theory explains the differential kinetics and stereoselectivities among substrates.
RESUMEN
A new class of tunable heterophosphole dimeric ligands have been designed and synthesized. These ligands have enabled the first examples of Cu-catalyzed hydrogenation of 2-substituted-1-tetralones and related heteroaryl ketones via dynamic kinetic resolution, simultaneously creating two contiguous stereogenic centers with up to >99 : 1 dr and 98 : 2 er. The ligand-Cu complexes were isolated and characterized by single crystal X-ray, and DFT calculations revealed a novel heteroligated dimeric copper hydride transition state.