Asymmetric Palladium‐Catalyzed Allylic Alkylation Using Dialkylzinc Reagents: A Remarkable Ligand Effect

Abstract

A serendipitously discovered palladium-catalyzed asymmetric allylic alkylation reaction with diorganozinc reagents, which displays broad functional group compatibility, is reported. This novel transformation hinges on a remarkable ligand effect which overrides the standard "umpolung" reactivity of allyl-palladium intermediates in the presence of dialkylzincs. Owing to its mild conditions, enantioselective allylic alkylations of racemic allylic electrophiles are possible in the presence of sensitive functional groups.

Luminescent zinc metal—organic framework (ZIF-90) for sensing metal ions, anions and small molecules

“…Our study data indicate that the luminescence intensity of ZIF-90 is highly sensitive to Cd 2+ and Cu 2+ ions owing to the interaction with imidazole nitrogen sites of organic ligands. The CrO 4 2− anions and small molecules such as acetone have the competition for absorption with ICA. The luminescence intensity of desolvated ZIF-90 increases proportionally with the concentration of Cd 2+ but decreases proportionally with the concentration of Cu 2+ , and decreases with the increase of CrO 4 2− anions and acetone in the emulsions of ZIF-90a.…”

“…The luminescence of ZIF-90a was gradually quenched with the increase of CrO 4 2− concentration (Fig. 7).…”

“…9). It is obvious that the absorption peak of ZIF-90a is almost overlapped by the absorption of CrO 4 2− . The CrO 4 2− competes for the absorption of light energy with the organic ligand and hence reduces the amount of light absorbed by the ligand thereby reducing the efficiency of energy transfer from the ligand to the metal ions of the frameworks.…”

Rhodium-catalysed asymmetric allylic arylation of racemic halides with arylboronic acids

“…of 21-25, respectively, with no further optimization of the reaction conditions. We found that vinylboronic acids can also be used as nucleophiles under the same reaction conditions (entries [25][26][27] to give 26-28, respectively. Here, good yields and high levels of enantioselectivity were observed when the reaction time was extended from one to four hours.…”

“…Pd-catalysed processes that convert a racemic mixture of starting materials into a new single-enantiomer product are commonly referred to as dynamic kinetic asymmetric transformations (DYKATs), as originally developed by Trost and co-workers 24 . DYKATs can now be used with a wide variety of stabilized nucleophiles and an array of metal catalysts 24 and several non-stabilized sp 3 -hybridized nucleophiles can now be used in certain related procedures [25][26][27][28] .…”