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234 Organic Chemistry Solutions Manual Purpose of the problem An exercise in using standard conjugate addition reactions in making molecules. Suggested solution The nitro group and the tertiary centre next to it leave only one option for this synthesis. The group is so anion-stabilizing that a tertiary amine is a strong enough base for this addition. + CO₂Me O₂N H CO₂Me There are two alternatives for the next compound but conjugate addition is so good acrylonitrile that we should prefer that route especially as the anion can then be stabilized and Et. The reaction needs only catalytic base as the initially formed adduct removes a from the next molecule of cyanoacetate. CN CN H H CN CN CN CN CN Problem 3 Suggest two different approaches to these compounds by conjugate addition of an Which do you prefer? 0 Ph Ph Purpose of the problem Exercising judgement in using standard conjugate addition reactions in making molecules. Suggested solution There is little to choose between the two routes to the first compound. Both unsatu compounds are easy to make and enol(ate) formation is easy in both cases. Perhaps the unsatu: ester will be more reliable at conjugate addition. Ph ? ? Ph Ph Ph Ph Ph The second compound could also be done either way, but both starting materials for route available while the unsaturated ketone needed for route B will have to be made. In both cases, enolizable ketone is being added to an enolizable unsaturated ketone, specific enol(ate)s wise. 0 0 0 0 ? ? A