Cyclization of the resulting keto aldehyde is an intramolecular aldol condensation. Base isrequired.(d)The frst step in this synthesis is the hydration of the alkene function to an alcohol. Notice thatthis hydration must take place with a regioselectivity opposite to that of Markovnikov’s ruleand therefore requires a hydroboration–oxidation sequence.Conversion of the secondary alcohol function to a carbonyl group can be achieved with any ofa number of oxidizing agents.Cyclization of the dione to the fnal product is a base-catalyzed intramolecular aldol conden-sation and was accomplished in 71% yield by treatment of the dione with a 2% solution ofsodium hydroxide in aqueous ethanol.18.30Intramolecular aldol condensations occur best when a fve- or six-membered ring is formed.Carbon–carbon bond formation therefore involves the aldehyde and the methyl group attached to
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This note was uploaded on 09/28/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.