ORGN 452 |
| The platinum-catalyzed rearrangement of β-keto propargylic alcohols (1) to 3-furanones (3) is described. Yields of 60-75% are obtained for several substrates. A mechanism proceeding via a platinated cyclic oxo-carbenium ion (2) is supported by the formation of 1,4 diketone byproducts (4). We hypothesize that alkyl migration from this intermediate yields 3-furanones, while in the cases where alkyl migration is slow, 1,4 diketones are formed. The distribution of products is dependant on the nature of alkyl groups at the propargylic and alkynyl positions of the substrates. Interestingly, when alkynyl cyclopropane substrates (R2 = cyclopropyl) are employed, the diketone product predominates, while in the case of aryl and alkyl acetylene substrates (R2 = phenyl), the major product is the 3-furanone.
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Modern Acetylene Chemistry
8:00 PM-10:00 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster
Division of Organic Chemistry |
