Ketones tandem dehydrogenation

A mixture of 1,4-dioxane and water is often used as the solvent for the conversion of aldehydes and ketones by H2Se03 to a-dicarbonyl compounds in one step (Eq. 8.117).331 Dehydrogenation of carbonyl compounds with selenium dioxide generates the a, (i-unsaturated carbonyl compounds in aqueous acetic acid.332 Using water as the reaction medium, ketones can be transformed into a-iodo ketones upon treatment with sodium iodide, hydrogen peroxide, and an acid.333 Interestingly, a-iodo ketones can be also obtained from secondary alcohol through a metal-free tandem oxidation-iodination approach. 

Matsuo and Aizawa71 have recently reported a new tandem reaction based on the dehydrogenation of ketones to the corresponding a,/3-unsaturated ketones, 77. They employed... 

The tandem sequence occurs between o-benzoylbenzyllithiums and furan-2-(5/7)-one168. The o-benzoyl-a-methoxybenzyllithium intermediate was generated by deprotonation of 2-methoxymethylphenyl phenyl ketone, 292, with LDA. Treatment of the a-lithiated product with furan-2-(5//)-one afforded the Michael addition/cyclization product, 293. The 9-aryl-9-hydroxy-3a,4,9,9a-tetrahydronaphtho[2,3-c]furan-l-(3//)-one 293 thus obtained was converted into the corresponding 9-aryl-4-methoxy-3a,4-dihydronaphtho[2,3-c]furan-] -(3//(-one 294 in good yield the subsequent dehydrogenation gave the desired product 4-methoxy-9-phenylnaphtho[2,3-c]furan-l(3/7)-one 295. 

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