A Lewis acid promoted oxidative cyclization.
Replacing trifluoroacetic acid with a catalytic amount of Lewis acid in the osmium mediated oxidative cyclization results in higher yielding reactions that can proceed nearly an order of magnitude faster. The osmium loading can also be reduced to as little as 0.2 mol %. Furthermore, these mildly acidic conditions are capable of tolerating a wide range of acid sensitive protecting groups that are incompatible with previous cyclization conditions.
Donohoe
Timothy J
TJ
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA, United Kingdom. timothy.donohoe@chem.ox.ac.uk
Winship
Paul C M
PC
Walter
Daryl S
DS
D000143:Acids / Q000737:chemistry*; D003500:Cyclization; D009992:Osmium / Q000737:chemistry; D010084:Oxidation-Reduction
D000143:Acids; D009992:Osmium