Activation
of B2pin2 with tBuLi
facilitates the Fe-catalyzed borylation of alkyl, allyl, benzyl, and
aryl halides via the formation of Li[B2pin2(tBu)] (1). The reaction of 1 with
a representative iron phosphine precatalyst generates the unique iron(I)
boryl complex [Fe(Bpin)(dpbz)2] (2).
While attractive, the iron-catalyzed coupling of arylboron reagents with alkyl halides typically requires expensive or synthetically challenging diphosphine ligands. Herein, we show that primary and secondary alkyl bromides and chlorides, as well as benzyl and allyl halides, can be coupled with arylboronic esters, activated with alkyllithium reagents, by using very simple iron-based catalysts. The catalysts used were either adducts of inexpensive and widely available diphosphines or, in a large number of cases, simply [Fe(acac)3] with no added co-ligands. In the former case, preliminary mechanistic studies highlight the likely involvement of iron(I)-phosphine intermediates.
A bimetallic system consisting of Cu-carbene and Mn-carbonyl co-catalysts was employed for carbonylative C–C coupling of arylboronic esters with alkyl halides, allowing for the convergent synthesis of ketones.
The reaction of 2-halobenzyl halides with the borate anion Li[(Ph)(t-Bu)Bpin] leads not only to the expected arylation at the benzyl position, but also to some Suzuki biaryl cross-coupling. Preliminary mechanistic investigations hint towards the intermediacy of benzyl iron intermediates that can either: (a) directly cross-couple with the aryl boron reagent to give observed monoarylated species, or (b) undergo oxidative addition of the aryl halide to generate the diarylated species on reaction with the boron-based nucleophile.
A synthetic route to an anti-cancer drug, lapatinib, was devised to support the development of a sustainable manufacturing process in South Africa. Quantitative metrics were employed to evaluate the sustainability...
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