Copper‐Catalyzed Enantioselective Allylic Alkylation with a γ‐Butyrolactone‐Derived Silyl Ketene Acetal

Abstract

Herein, we report aC u-catalyzed enantioselective allylic alkylation using a g-butyrolactone-derived silyl ketene acetal. Critical to the development of this work was the identification of an ovel mono-picolinamide ligand with the appropriate steric and electronic properties to affordt he desired products in high yield (up to 96 %) and high ee (up to 95 %). Aryl, aliphatic,a nd unsubstituted allylic chlorides bearing ab road range of functionality are well-tolerated. Spectroscopic studies reveal that aC u I species is likely the active catalyst, and DFT calculations suggest ligand sterics play an important role in determining Cu coordination and thus catalyst geometry.

CuH-Catalyzed Regio- and Enantioselective Hydrocarboxylation of Allenes: Toward Carboxylic Acids with Acyclic Quaternary Centers

“…All-carbon quaternary stereocenters, a structural feature that can impart significant chemical and biological impact to a molecule, are critical to many synthetic and medicinal applications. − Consequently, catalytic and enantioselective approaches for constructing all-carbon quaternary centers, especially functionalized stereocenters, are highly desirable. − Carboxylic acids, a chemically versatile functional group, that can bear an α-stereogenic center often serve as useful synthetic intermediates. − More importantly, α-chiral carboxylic acid derivatives themselves constitute an essential class of compounds in pharmaceutical, agrochemical, and natural product arenas (Figure A). − Methods for generating enantioenriched α-chiral carboxylic acids have long been sought after . Prominent synthetic strategies targeting α-chiral carboxylic acids or esters via asymmetric catalysis include hydrogenation of α,β-unsaturated carboxylic acids, carbene-induced C–H insertion with diazoacetates, − enantioselective protonation , or hydrogen atom transfer processes, and α-functionalization of carboxylic acid derivatives. − Nonetheless, catalytic access to enantioenriched acyclic carboxylic acids or esters featuring an all-carbon α-quaternary stereocenter remains challenging. , In this regard, common synthetic methods include allylic alkylation of geometrically pure alkenes, − often with superstoichiometric organometallic reagents, and α-functionalization of carboxylic acid derivatives, − …”

Cross-Dimerization of 2,5-Dihydrofuran with Conjugated Dienes Catalyzed by (Chiral Diene)ruthenium(0) Complexes and Origins of the Enantioselectivity

“…The absolute configuration of 6aa was determined to be the S -form, which was confirmed by the pyridinium chlorochromate (C 5 H 6 NO 3 ClCr; PCC) oxidation to a lactone followed by ozonolysis leading to a reported compound; (4 S )-4-(2-oxopropyl)­dihydrofuran-2­(3 H )-one (Scheme ). Although there are reported methods for synthesizing chiral γ-lactones with a substituent at the α-position, this method is also a unique reaction for synthesizing chiral β-substituted-γ-lactones. The reaction at 0 °C gave 6aa in 80% yield, although the reaction was very sluggish.…”

Silver Catalyzed Decarbonylative [3 + 2] Cycloaddition of Cyclobutenediones and Formamides

“…N , O -Acetal was easily converted to hemiacetal under acid condition. Upon heating the product 3aa in THF at 65 °C in the presence of H 2 SO 4 , 4 was isolated in 66% yield, which could be further alkylated to 5 or 6 using Grignard reaction or HWE olefination [ 35 ], respectively ( Scheme 2 ).…”