Ketones intramolecular diene coupling

E.iii. Aldehydes and Ketones as TVapping Agents Intramolecular Diene Coupling... 

In order to introduce functionality at key positions, an intramolecular Diels-Alder reaction with furan as the diene component was planned. Suzuki coupling of the previously mentioned 105 with furan-3-boronic acid 106 gave compound 107, which was N-tosylated to 108. Construction of the dienophile portion was performed as in the previous case, by addition of vinylmagne-sium bromide to give 109, followed by MnC>2 oxidation to give the cyclization precursor, which was immediately heated at 120 °C in toluene and afforded compound 110, which incorporates an oxygen atom at both the ketone and vinyl chloride positions of welwistatin (Scheme 24). 

A number of related reactions, which occur by different mechanisms, have been reported. The intramolecular reaction of halo-malonates under carbon monoxide gives cyclic ketones (Eq. 5) [31,32]. This proceeds by mechanism C. Halo-malonates also couple with unsaturated compounds such as 1,3-dienes... 

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