The utility of vinyl ethers and vinyl esters in the Khand reaction. The value of vinyl esters as ethylene equivalents and a modified synthesis of (+)-taylorione as an example

The behaviour of various oxygenated alkenes in the Khand cyclisation reacti on has been studied. Although several vinyl ethers reacted to give the expe cted oxygenated cyclopentenone products, usually with good levels of regios electivity, the use of vinyl esters was found to afford, as the major produ cts, reduced cyclopentenones in which the carbon-oxygen bond had been cleav ed. This unexpected reaction was developed into an alternative procedure to using ethylene gas in the Khand reaction and was found to be applicable wi th a variety of alkyne substrates. The method was then extended to form the key step in the synthesis of the natural product (+)-taylorione (and (+)-n ortaylorione). (C) 2001 Elsevier Science B. V. All rights reserved.