TY - JOUR
T1 - Competing amination and C-H arylation pathways in Pd/xantphos-catalyzed transformations of binaphthyl triflates
T2 - Switchable routes to chiral amines and helicene derivatives
AU - Ruch, Aaron A.
AU - Handa, Sachin
AU - Kong, Fanji
AU - Nesterov, Vladimir N.
AU - Pahls, Dale R.
AU - Cundari, Thomas R.
AU - Slaughter, Legrande M.
N1 - Publisher Copyright:
© 2016 The Royal Society of Chemistry.
PY - 2016
Y1 - 2016
N2 - A Pd(OAc)2/xantphos catalyst system was found effective for benzylaminations of binaphthyl 2-triflates bearing a variety of alkyl, benzyl, and substituted phenyl substituents at the 2′-position. With 2′-aryl substituents, an intramolecular Pd-catalyzed C-H arylation was observed as a competing side reaction under some conditions. By adjusting the solvent and quantity of the amine, the reaction was optimized to favor either the amination or the C-H arylation pathway, affording two distinct and potentially useful sets of products. The amines represent tunable chiral ligand precursors, while the C-H arylation pathway affords a series of benzofused [5]helicene derivatives. Kinetic studies and activation parameters for the C-H arylation pathway, supported by DFT calculations, are consistent with a concerted metalation-deprotonation (CMD) mechanism involving a Pd-bound carbonate as the base. Xantphos is proposed to facilitate the turnover-limiting inner-sphere CMD step by acting as a hemilabile ligand, while its wide bite angle engenders a low reductive elimination barrier.
AB - A Pd(OAc)2/xantphos catalyst system was found effective for benzylaminations of binaphthyl 2-triflates bearing a variety of alkyl, benzyl, and substituted phenyl substituents at the 2′-position. With 2′-aryl substituents, an intramolecular Pd-catalyzed C-H arylation was observed as a competing side reaction under some conditions. By adjusting the solvent and quantity of the amine, the reaction was optimized to favor either the amination or the C-H arylation pathway, affording two distinct and potentially useful sets of products. The amines represent tunable chiral ligand precursors, while the C-H arylation pathway affords a series of benzofused [5]helicene derivatives. Kinetic studies and activation parameters for the C-H arylation pathway, supported by DFT calculations, are consistent with a concerted metalation-deprotonation (CMD) mechanism involving a Pd-bound carbonate as the base. Xantphos is proposed to facilitate the turnover-limiting inner-sphere CMD step by acting as a hemilabile ligand, while its wide bite angle engenders a low reductive elimination barrier.
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U2 - 10.1039/c6ob01102k
DO - 10.1039/c6ob01102k
M3 - Article
C2 - 27507596
AN - SCOPUS:84984623360
SN - 1477-0520
VL - 14
SP - 8123
EP - 8140
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
IS - 34
ER -