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Enantioselective formation of bicyclic lactones by rhodium-catalyzed intramolecular CH-insertion reactions

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Published in Helvetica Chimica Acta. 1994, vol. 77, no. 3, p. 645-654
Abstract The decomposition of cyclohexyl diazoacetate (5a) in the presence of the chiral [Rh2{(2S)-mepy}4] catalyst leads to a 3:1 cis/trans mixture of bicyclic lactone 6a with an enantiomeric excess of 95–97% (cis) and 90% (trans). The conformationally rigid tert-butyl derivatives 5b and 5c afford, in the presence of the same catalyst, 6b and 6c, respectively, via insertion into the equatorial C-H bonds exclusively, with ee's of ca. 95%. A remarkable degree of induction (92–95%) results in the lactone 6g upon decomposition of 1-isopropyl-2-methylpropyl diazoacetate (5g). The diazoacetates derived from 1-methylcyclohexanol, cyclopentanol and 1-methylcyclopentanol (5d–f) afford under similar conditions insertion products with higher diastereoselectivity, but significantly lower enantioselectivity. Other dirhodium catalysts are less efficient.
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MULLER, Paul, POLLEUX, Philippe. Enantioselective formation of bicyclic lactones by rhodium-catalyzed intramolecular CH-insertion reactions. In: Helvetica Chimica Acta, 1994, vol. 77, n° 3, p. 645-654. https://archive-ouverte.unige.ch/unige:84791

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