A new
method for the decarboxylative coupling of alkyl N-hydroxyphthalimide esters (NHP esters) with aryl
iodides is presented. In contrast to previous studies that form alkyl
radicals from carboxylic acid derivatives, no photocatalyst, light,
or arylmetal reagent is needed, only nickel and a reducing agent (Zn).
Methyl, primary, and secondary alkyl groups can all be coupled in
good yield (77% ave yield). One coupling with an acid chloride is
also presented. Stoichiometric reactions of (dtbbpy)Ni(2-tolyl)I with
an NHP ester show for the first time that arylnickel(II) complexes
can directly react with NHP esters to form alkylated arenes.
A high-yielding protocol for the palladium-catalyzed silylation of terminal alkenes using silyl halides is reported. This method allows facile conversion of styrenes to E-β-silyl styrenes using either TMSI or TMSCl/LiI. Terminal allyl silanes with good E:Z ratios are also readily accessed from α-olefins by this method. When combined with existing technology, this transformation provides a powerful strategy to selectively functionalize the vinyl or allylic position of terminal alkenes.
An improved method for the reductive coupling of aryl and vinyl bromides with alkyl halides is presented that achieves high yields for a variety of substrates at rt with a low (2.5 to 0.5 mol%) catalyst loading. Under the optimized conditions, difficult substrates, such as unhindered alkenyl bromides, can be coupled to furnish the desired olefins with minimal diene formation and good stereoretention. These improved conditions also work well for aryl bromides. For example, a gram-scale reaction is demonstrated with 0.5 mol% catalyst loading, while reactions at 10 mol% catalyst loading completed in as little as 20 min. Finally, a low-cost single-component pre-catalyst, (bpy)NiI2, is introduced that is both air- and moisture-stable over a period of months.
So leicht ist Silylieren! Eine palladiumkatalysierte Silylierung endständiger Alkene mit Silylhalogeniden wird beschrieben. Styrole werden durch Einwirkung von Iodtrimethylsilan (TMSI) in E‐β‐Silylstyrole umgewandelt (siehe Schema), und auch endständige Allylsilane sind mit guten E/Z‐Verhältnissen aus α‐Olefinen erhältlich.
For the first time, nickel-catalyzed silyl-Heck reactions are reported. Using simple phosphine-supported nickel catalysts, direct activation of silyl triflates has been achieved. These results contrast earlier palladium-catalyzed systems, which require iodide additives to activate silyl-triflates. These nickel-based catalysts exhibit good functional group tolerance in the preparation of vinyl silanes, and unlike earlier systems, allows for the incorporation of trialkylsilanes larger than Me3Si.
This chapter describes the procedure for nickel‐catalyzed cross‐coupling of aryl halides with alkyl halides: ethyl 4‐(4‐(4‐methylphenylsulfonamido)‐phenyl)butanoate. It presents some of the important points to be considered, the conditions that need to be maintained, characterization data, and the reagents required, as well as the techniques used and the equipment setup that are vital to carrying out the process. The chapter also describes the hazards associated with working with chemicals and the ways to deal with these hazards. While alkyl halides are far more abundant than alkyl organometallic reagents, the largest commercially available pools of aliphatic electrophile diversity are alcohols, amines, and alkanoic acids.
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