Highly Enantioselective Aryl Transfer to Aldehydes:  A Remarkable Effect of Sulfur Substitution in Amino Thioacetate Ligands

Abstract

Chiral amino thioacetate ligands were prepared from the corresponding amino alcohols and used as catalysts for enantioselective aryl transfer reaction. The amino thioacetates were remarkably superior to the corresponding amino alcohols. Low catalyst loadings of only 1-2.5 mol % were sufficient to achieve excellent enantioselectivity as well as high conversion in short reaction time. The results reveal that the thioacetoxy moiety of the amino thioacetates has a surprisingly beneficial effect in enhancing the asymmetric induction.

Planar-Chiral Phosphine-Olefin Ligands Exploiting a (Cyclopentadienyl)manganese(I) Scaffold To Achieve High Robustness and High Enantioselectivity

“…A straightforward method of preparing these compounds is an asymmetric nucleophilic addition of an aryl nucleophile to an appropriate arylaldehyde. The reactions between an arylzinc reagent and an arylaldehyde have been studied in the presence of a chiral Lewis base with fair success . The transition-metal-catalyzed variants of these asymmetric reactions have been developed as well.…”

Highly Enantioselective Arylation of Aldehydes and Ketones Using AlArEt2(THF) as Aryl Sources

“…Bolm and co-workers later developed systems for the enantioselective synthesis of diarylmethanols through the use of arylboronic acids or arylboranes in combination with Et 2 Zn in situ to generate various arylzinc compounds for the asymmetric addition reactions. The studies extended the reaction scope from the phenyl addition to aryl addition reactions, and this strategy has been further demonstrated by Dagmen, Chan, Zhao, Braga, and Jin . The enantioselective aryl transfer to aldehydes has also been reported employing a zinc reagent prepared in situ from ZnCl 2 and phenylmagnesium bromide by Soai et al or aryllithium by Walsh and a co-worker .…”

Chiral 1,1′‐binaphthylazepine‐derived amino alcohol catalyzed asymmetric aryl transfer reactions with boroxine as aryl source

“…9 However, the arylboronic acid protocol demands a huge excess of diethylzinc (6-7 equiv) for the boron-zinc transmetalation due to the acidity of boronic acid. So, further improvements on this approach were focused on the amelioration of the aryl sources [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and effectual ligands. 8 Triphenylboranes, [17][18][19] triarylborane ammonia complexes, 20 and phenylboroxines [21][22][23] were all found to be viable aryl sources (see Fig.…”