Remarkably Stable (Me₃Al)₂⋅DABCO and Stereoselective Nickel‐Catalyzed AlR₃ (R=Me, Et) Additions to Aldehydes

Abstract

Weigh it out in air! The DABAL reagent (Me3Al)2⋅(DABCO) (DABCO=1,4‐diazabicyclo[2.2.2]octane) can be easily handled under normal laboratory conditions. Furthermore, chiral secondary alcohols can be efficiently prepared from prochiral aldehydes (see scheme; TOF=turnover frequency) by using either DABAL or AlR3 reagents (R=Me, Et). Thus, DABAL can be used as an efficient, convenient alternative to the Schumann–Blum reagent.

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

“…[362] Eine ganz andere 1,2-Addition ist die enantioselektive Alkylierung der Aldehyde 236 mit den DABCO-Trialkylaluminiumkomplexen 237 (DABCO: 1,4-Diazabicylco[2.2.0]octan) und einem Nickel/Phosphoramidit-Katalysator (Schema 75). [363] In Gegenwart des Liganden ent-L2a (Abbildung 4) entstanden die chiralen sekundären Alkohole 238 mit Ausbeuten bis 95 % und hohen ee-Werten (bis 95 %). Einige Produkte wurden auch ohne DABCO mit hohem Enantiomerenüberschuss (bis 98 %) gebildet, aber bei den meisten Substraten führte der DABCO-Trialkylaluminiumkomplex zu höheren Enantioselektivitäten.…”

Friedel–Crafts‐Type Alkylation with Bromodifluoro(phenylsulfanyl)methane through α‐Fluorocarbocations: Syntheses of Thioesters, Benzophenones and Xanthones

“…We believe this can be attributed to the presence of the phenylsulfanyl group in the molecule, which contributes to substantial charge delocalization. In the 13 C NMR spectra, complex patterns downfield from the triplet signal (δ C = 119.26 ppm, J = 336.37 Hz) corresponding to the gem-difluoro-substituted carbon atom of compound 1 were observed after 24 h of mixing compound 1 with SnCl 4 . Unfortunately, we were unable to identify or assign the signals to carbon atoms corresponding to these complex patterns.…”

“…In an effort to study this reaction in detail with the aim of achieving reaction optimization, obtaining fluorinated product and altering the selectivity for 3a and 4a, an array of Lewis acids were screened, including [11] AlCl 3 , AlMe 3 , EtAlCl 2 , [12] DABAL-Me 3 , [13] [BMIM]Al 2 Cl 7 , [14] [16] were also investigated. When using milder Lewis acids, no thioester, benzophenone or fluorinated product could be isolated, and most of the aromatic compound 2a was recovered.…”

DABAL-Me3: A Versatile Methylating Agent

“…3 (B) Methylation of aryl and vinyl halides is another example of a very efficient route of forming C-C bonds. DABAL-Me 3 is quite capable of carrying out this transformation.…”