A Straightforward Route to E-γ-Aryl-α-oxobutenoic Esters by One-step Acid-catalysed Crotonisation of Pyruvates
31 December 2001 (online)
A new and highly simple method for the synthesis of E-γ-aryl-α-oxobutenoic esters is described. This unprecedented one-step procedure is based on an unexpected nucleophilic reactivity of alkyl pyruvates towards aromatic aldehydes in refluxing dichloromethane, when using catalytic amounts of Cu(OTf)2 and in the presence of stoichiometric amounts of trimethyl orthoformate in the case of electron-rich aldehydes. Under these conditions, yields obtained are uniformly higher than those obtained by previous multistep procedures.
benzylidenepyruvate - crotonisation - copper (II) triflate - trimethyl orthoformate - heterodiene