Formation of spiro ketolactones versus alkoxy radical fragmentation-promoted three-atom ring enlarged lactones from cyclic ketones |
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Authors: | Alfred Hassner Tarun K Pradhan |
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Institution: | Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel |
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Abstract: | A dual pathway from readily available 2-allyl-2-carboethoxycycloalkanones 1 provides a new facile stereoselective synthesis either of functionalized spiro ketolactones 4 or of ring enlarged lactones 7 in one-step. Thus, iodination of 5-8-membered 2-allyl-2-carboethoxycycloalkanones 1a-d led, in excellent yields, to spiro ketolactones 4a-d, respectively, as single stereoisomers. On the other hand, iodination of 1a-d under alkoxy radical fragmentation conditions via incipient hemiketals produced the 8-, 9-, 10-, or 11-membered, three-atom ring enlarged, poly-functionalized lactones 7a-c as two stereoisomers and 8 as a single isomer. |
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Keywords: | Stereoselective Spirolactone Lactone Radical fragmentation Hemiketals Ring enlargement |
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