Enantioselective rhodium-catalysed nucleophilic allylation of cyclic imines
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Date
30/06/2015Item status
Restricted AccessEmbargo end date
31/12/2100Author
Hepburn, Hamish Bruce
Metadata
Abstract
A highly enantioselective and diastereoselective rhodium-catalysed addition of
potassium allyltrifluoroborates to cyclic imines is described within. By utilising
rhodium-chiral diene complexes, a wide range of cyclic imines were successfully
allylated in high yields and enantioselectivities. Using a variety of more highly
substituted allyl reagents, additional stereocentres and further molecular complexity
was achieved with good yields, enantioselectivities and diastereoselectivities.
Investigations involving isomeric allyl species and deuterated allyl species provided
results that gave mechanistic insight, leading to the proposal of a plausible
mechanistic pathway and suggested the formation of interconverting allylrhodium
intermediates. Furthermore, during these investigations, a highly interesting isomerisation of the
allylrhodium intermediate was discovered. Such isomerisation led to the in situ
formation of the more complex allylrhodium intermediates which led to complex
products upon allylation with cyclic imines that would be difficult to synthesis via
other methods. This isomerisation was found to occur for a range of cyclic imines
and disubstituted allyltrifluoroborates, proceeding in good yields and diastereomeric
ratios. Deuterium studies indicate it is probable that this isomerisation proceeds via a
1,4 rhodium migration and a plausible mechanism is proposed explaining both the
connectivity of the products and the relative stereochemistry.