Self‐Assembled Bidentate Ligands for the Nickel‐Catalyzed Hydrocyanation of Alkenes

Lewis Acid Controlled Regioselectivity in Styrene Hydrocyanation

“…The theoretical calculations were supported by NMR spectroscopic investigations. In fact, the 31 P NMR spectrum of an equimolar mixture of bippp and AlCl 3 in benzene-d 8 clearly shows a shift of the phosphorus resonance from 130 to 160 ppm. [16] In the case of the corresponding complex…”

“…Branched nitriles were the only products observed and the deuterium incorporation proceeded exclusively in the bmethyl position. Moreover, h 3 -allyl complexes (Scheme 2) have also been described as intermediates in the hydrocyanation of dienes [8,12] and vinylarenes [5a, 9] and in the isomerization of 2-methyl-3-butenenitrile to 3-pentenenitrile. [13] The h 3 -benzyl intermediate was generally assumed to be the preferred intermediate formed after insertion of a vinylarene into the NiÀH bond, rather than the linear alkyl intermediate (Scheme 2).…”

“…In the presence of AlCl 3 a linear/ branched ratio of 73:27 was observed, whereas the linear product was only obtained in traces (detected by GC) in the absence of Lewis acid. The lower conversion and selectivity might be due to the different purification procedure applied for styrene and styrene-d 8 . The latter was degassed and used as received, but styrene was also filtered and distilled.…”

“…Recently, self-assembled bidentate phosphine ligands have been applied in the Ni-catalyzed hydrocyanation of styrene. [8] However, open questions still remain on how to improve the performance of the catalyst, and particularly on the role of the Lewis acid co-catalyst [9] that generally has to be applied in the hydrocyanation of nonconjugated alkenes. The promotional effect on the reactivity and the influence on the regioselectivity have been investigated mainly for monoolefins by using several Lewis acids, [10] such as ZnCl 2 , AlCl 3 , and BPh 3 .…”

Cooperative Catalysis with First‐Row Late Transition Metals

“…[91] Although this provides a very elegant way to prepare new ligand systems, with the advantage of creating larger libraries due to the higher availability of building blocks, the self-assembly does not extend to the level of cooperative catalysis, as the ligands do not actively participate during substrate conversion but are merely configured using non-covalent H-bonding interactions. In general, despite the "synzymatic" nature of some of these supramolecular catalysts, there is no true cooperative aspect as yet incorporated in most of these concepts, nor are firstrow transition metals exploited in this way.…”