Palladium-Catalyzed Decarboxylative Asymmetric Allylic Alkylation of β-ketoesters: An Unusual Counterion Effect
作者:Barry M. Trost、Benjamin Schäffner、Maksim Osipov、Donna A. A. Wilton
DOI:10.1002/anie.201007803
日期:2011.4.4
allyl chloroformate and their β‐ketoesters by using the same catalyst system (see scheme; dba=dibenzylideneacetone, 1,2‐DCE=1,2‐dichloroethane, THF=tetrahydrofuran). The details of this remarkable effect were investigated by performing scavenging experiments and a variety of substrates were successfully used in the procedure.
Enantioselective Alkylation of β-Keto Esters by Phase-Transfer Catalysis Using Chiral Quaternary Ammonium Salts
作者:Eun Joo Park、Mi Hee Kim、Dae Young Kim
DOI:10.1021/jo0401772
日期:2004.10.1
Catalytic enantioselectivealkylationpromoted by a quaternary ammonium salt from cinchonine as a phase transfer catalyst is described. Treatment of cyclo β-ketoesters with alkyl halide under mild reaction conditions afforded the corresponding α-alkylated β-ketoesters in moderate to excellent yields with high enantiomeric excesses
Radical Chain Reactions of α-Azido-β-keto Esters with Tributyltin Hydride. A Novel Entry to Amides and Lactams through Regiospecific Nitrogen Insertion
A variety of acyclic and carbocyclic alpha-azido-beta-keto esters have been readily prepared from the parent dicarbonyl compounds, and their radical chain reactions with tributyltin hydride have been investigated. These reactions normally result in efficient production of alkoxycarbonyl-substituted amides and lactams and thence provide a new, useful method for regiospecific nitrogen insertion of keto ester compounds. The likely mechanism entails initial addition of tributylstannyl radical to the azido moiety to give a stannylaminyl radical, which readily undergoes intramolecular three-membered cyclization onto the ketone group to form an alkoxyl radical. The alkoxyl radical then undergoes regiospecific beta-scissian to form a stable ring-opened radical that is eventually reduced by tributyltin hydride to propagate the chain. With certain substrates, concomitant deazidation occurs to an important extent. This process, which is unusually observed in radical reactions of alkyl azides, is ascribed to addition of the stannyl radical to the terminal azido nitrogen; subsequent fragmentation of the ensuing 1,3-triazenyl adduct gives stannyl azide and a deazidated alkyl radical, resonance-stabilized by the adjacent carbonyl groups. The radical reactions of 2-azido-2-(ethoxy-carbonyl)-1-tetralone with allyltributylstannane and allyltriphenylstannane have also been investigated with the (missed) aim to achieve nitrogen insertion and concomitant allylation.
Remarkable rate enhancement of palladium-catalyzed allylic alkylation in water using a colloidal dispersion system
作者:Shū Kobayashi、William W.-L Lam、Kei Manabe
DOI:10.1016/s0040-4039(00)01027-3
日期:2000.8
The rate of palladium-catalyzed allylic alkylation was dramaticallyenhanced in a colloidal dispersion system created by a neutral surfactant, Triton X-100, in water.
A Facile Synthesis of (n+3) and (n+4) Ring-Enlarged Lactones as well as of Spiroketolactones from n-Membered Cycloalkanones
作者:Alfred Hassner、Tarun Pradhan
DOI:10.1055/s-2007-990820
日期:2007.11
simple ethyl l-allyl-2-oxocycloalkanecarboxylates, resulting from a three-atom ringenlargement. Similarly, four-atom ringenlargements of a 5- to 9- and 6- to 10-membered-ring lactones were achieved. Alkoxy radical fragmentation (ARF) with hypervalent iodine was used as the key step for these ring expansions. The ringenlargement proceeds via an unstable hemiketal intermediate, which was isolable in some