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. 2012 Oct 17;134(41):16967-16970.
doi: 10.1021/ja3079362. Epub 2012 Oct 5.

Mechanistic investigation of the nickel-catalyzed Suzuki reaction of N,O-acetals: evidence for boronic acid assisted oxidative addition and an iminium activation pathway

Kevin T Sylvester #, Kevin Wu #, Abigail G Doyle

Mechanistic investigation of the nickel-catalyzed Suzuki reaction of N,O-acetals: evidence for boronic acid assisted oxidative addition and an iminium activation pathway

Kevin T Sylvester et al. J Am Chem Soc. .

Abstract

The mechanism of a recently reported Suzuki coupling reaction of quinoline-derived allylic N,O-acetals has been studied using a combination of structural, stereochemical, and kinetic isotope effect experiments. The data indicate that C-O activation is facilitated by Lewis acid assistance from the boronic acid coupling partner and an ionic S(N)1-like mechanism accounts for oxidative addition. In this context, we demonstrate the first direct observation of oxidative addition to a quinolinium salt. Notably, this mechanism is distinct from the more commonly described S(N)2(')-type oxidative addition of low-valent transition metals to most allylic electrophiles.

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Figures

Figure 1
Figure 1
Solid-state structure of olefin-complex 3 at 30% probability ellipsoids. Toluene solvent molecule omitted for clarity. Hydrogen atoms omitted for clarity, except those attached to C37 and C38.
Figure 2
Figure 2
Solid-state structure of Ni-allyl complex 5-triflate at 30% probability ellipsoids. Dichloromethane molecules, disorder on ethyl group of carbamate, and all hydrogen atoms omitted for clarity.
Scheme 1
Scheme 1
Possible Mechanisms for Csp3–O Activation
Scheme 2
Scheme 2
Stoichiometric Studies of Oxidative Addition
Scheme 3
Scheme 3
Studies with Quinolinium Triflate
See this image and copyright information in PMC

References

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