2-Cyclohexenone Cyclopentadiene

Cationic oxazaborolidines derived from a,a-diphenylpyrrolidine-2-methanol have been examined and shown to considerably extend the range of dienophiles that are responsive to the catalysts." The best proton source for activation of these catalysts is triflimide, (CF3S02)2NH.100 For example, cyclohexenone and cyclopentadiene react with 93% enantioselectivity using catalyst J. 

Hydroxyphenylcyclohexanes Cyclohexanols—see Cahx[4]cyclohexanols Cyclohexanones—see Cahx [4] cyclohexanones Cyclohexenones—see Aryl-2-cyclohexenones 4-Cyclohexylphenol, formation of 613 Cyclopentadiene 5-carboxyUc acid 1057 Cyclopropanation, asymmetric 697 Cytochrome P-450 linked microsomal Papaver enzyme 1216 Cytotoxicity 654 CZE 971-974... 

Following is a retrosynthetic scheme for the synthesis of the tricyclic diene on the left. Show how to accomplish this synthesis from 2-bromopropane, cyclopentadiene, and 2 - cyclohexenone. 

These reactions are broadly classified as normal and inverse electron demand Diels-Alder reactions. In normal electron demand Diels-Alder reactions (NED D-AR), diene system acts as electron-rich HOMO system and dienophile as electron-seeking LUMO system, while in inverse electron demand Diels-Alder reactions (lED D-AR), diene system serves as LUMO and dienophile as HOMO [22]. For example, reaction of cyclopentadiene 31 with methyl acrylate gives 32 in NED D-AR [23] and of ethoxyethylene with P-(2-cyclohexenone)-ethyl acrylate 33 gives 34 in NED D-AR [24]. 

---