Enantioselective rhodium-catalysed addition of allylboron reagents to cyclic imines and enantioselective nickel-catalysed Michael additions of 2-acetylazaarenes to nitroalkenes
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Date
28/06/2016Author
Chotsaeng, Nawasit
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Abstract
Enantioselective Rhodium-Catalysed Addition of Allylboron Reagents
to Cyclic Imines
Rhodium-catalysed enantioselective allylation reaction of imines in the presence of
chiral diene ligands has been investigated. Under the optimised conditions, cyclic imines
provided homoallylic amines in high yield and excellent enantioselectivities. The
reaction most likely proceeds via allylrhodium(I) intermediates, and represents the first
rhodium-catalysed enantioselective nucleophilic allylation of π-electrophiles with
allylboron compounds. Furthermore, the allylations display a strong preference for
carbon–carbon bond formation at the more substituted terminus of the allyl fragment of
the allyltrifluoroborate. To demonstrate the utility of the allylation products,
representative manipulations were conducted. Enantioselective Nickel-Catalysed Michael Additions of
2-Acetylazaarenes to Nitroalkenes
An enantioselective Michael addition of acylazaarenes with α-substituted
β-nitroacrylates in the presence of a chiral Ni(II)–bis(oxazoline) complexes has been
developed. A range of azaaryl nucleophiles were shown to react with a variety of
nitroalkenes to construct highly functionalised Michael addition products which contain a stereogenic all-carbon quaternary stereocentre with moderate to high yields and
enantioselectivities. A possible mechanism for this reaction has been proposed.