Substrate requirements for palladium-aluminium triflate co-catalysed hydromethoxycarbonylation reactions of alkynes bearing oxygen atoms
The palladium diacetate-aluminium triflate combination is an effective catalyst for the hydromethoxycarbonylation reaction of isolated alkenes and alkynes. However, its application in the hydromethoxycarbonylation of oxygen atom-bearing alkynes is non-trivial: the position relative to the alkyne (e.g., allylic, homoallylic) and nature of the oxygen atom determine the success of the transformation. We detail the minimum structural requirements for a successful outcome with ether-containing alkyne substrates and hydroxyl-containing analogues. In general, the oxygen atom has a detrimental effect on the outcome of the hydromethoxycarbonylation reaction, which can be overcome in many instances. The presence of the oxygen atom(s) causes decreases in the rate of the reaction compared to aliphatic alkynes and the closer the oxygen atom is to the triple bond, the more pronounced the effect. The chemistry is demonstrated on complex substrates derived from 5 and 6-carbon sugars in optimised reactions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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