1. The Diels-Alder Reaction Synthetic method for preparing compounds containing a cyclohexene ring

2. conjugated diene alkene (dienophile) cyclohexene + In general...

3. transition state via

4. concerted mechanism cycloaddition pericyclic reaction a concerted reaction that proceeds through a cyclic transition state Mechanistic features

5. conjugated diene alkene (dienophile) cyclohexene + Recall the general reaction... The equation as written is somewhat misleading because ethylene is a relatively unreactive dienophile.

6. What makes a reactive dienophile? The most reactive dienophiles have an electron-withdrawing group (EWG) directly attached to the double bond. Typical EWGs C O CN C CEWG

7. + benzene 100°C (100%) H2CH2CH2CH2C CHCH CH 2 H2CH2CH2CH2C CH CHO CHOExample

8. + benzene 100°C (100%) H2CH2CH2CH2C CHCH H2CH2CH2CH2C CH CHO CHOExample CHOvia:

9. + benzene 100°C (100%)OO O Example H2CH2CH2CH2C CHC CH 3 H3CH3CH3CH3COO O

10. + benzene 100°C (100%)OO O Example H2CH2CH2CH2C CHC CH 2 CH 3 H3CH3CH3CH3COO O via: H3CH3CH3CH3C O O O

11. + benzene 100°C (98%) H2CH2CH2CH2C CHCH CH 2 Acetylenic Dienophile O CCOCH 2 CH 3 CH 3 CH 2 OCC O COCH 2 CH 3 OO

12. syn addition to alkene cis-trans relationship of substituents on alkene retained in cyclohexene product Diels-Alder Reaction is Stereospecific* *A stereospecific reaction is one in which stereoisomeric starting materials give stereoisomeric products; characterized by terms like syn addition, anti elimination, inversion of configuration, etc.

13. only product + H2CH2CH2CH2C CHCH CH 2 Example C C C6H5C6H5C6H5C6H5 COH HH OH C6H5C6H5C6H5C6H5 H COH O

14. only product + H2CH2CH2CH2C CHCH CH 2 Example C C C6H5C6H5C6H5C6H5 COH H HO H C6H5C6H5C6H5C6H5H COH O

15. Cyclic dienes yield bridged bicyclic Diels-Alder adducts.

16. + C C COCH 3 H HO CH 3 OC O H H COCH 3 O O

17. is the same as H H COCH 3 O O H H O O