1559Tch18323-34311/3/0511:12Page325 Keysohe Chapter325 The wide range of chemistry is unde standable in terms of just three fundamental mechanisti sses 1.Electrophilic addition to carbonyl oxygen,e.g x-2 COH :OH C( 2.Nucleophilic addition to carbonyl carbon.. Co: :0:L c= +一x- 3.Nucleophilic addition to the B-carbon.e.g. Practice by writing mechanisms for examples in the text for which specific mechanisms are not pictured Use the appropriate mechanism above to starand follow it with the behavior expected for the product of that ste you understand the mechanisms. ones or ena ation Micha the retrosynthetic analysis for compounds containing six-membered rings six-membered ringsis best seen by the resonance forms in these compounds: Note in particular the presence of positive character at the -carbon as well as at the carbonyl carbon. The wide range of enone chemistry is understandable in terms of just three fundamental mechanistic processes. 1. Electrophilic addition to carbonyl oxygen, e.g., 2. Nucleophilic addition to carbonyl carbon, e.g., 3. Nucleophilic addition to the -carbon, e.g., Practice by writing mechanisms for examples in the text for which specific mechanisms are not pictured. Use the appropriate mechanism above to start, and follow it with the behavior expected for the product of that step. Once you understand the mechanisms, concentrate on the synthetic applications of the process. Focus on the carbon–carbon bond-forming examples, with particular emphasis on the Michael addition, the 1,4-addition of enolates to enones or enals. The combination Michael addition–aldol condensation provides a powerful means of synthesis of six-membered rings, the Robinson annulation. Don’t worry about all these people’s names; learn the retrosynthetic analysis for compounds containing six-membered rings. Cyclohexenone O 3 3 1 1 2 2 Substituted and functionalized six-membered rings 1,5-Dicarbonyl compound O O O O

O O
C O  O C C C CN C C CN  C  C O Li O C CH3 CH3 C C  Li C C C OH OH OH C C    H C C C C C C O C C C  C C C   C C C C C C O O  O  Keys to the Chapter • 325 1559T_ch18_323-343 11/3/05 11:12 Page 325