Asymmetric induction in Diels-Alder reactions of o-quinodimethanes

✍ Scribed by James L. Charlton

• Publisher: Elsevier Science
• Year: 1985
• Tongue: French
• Weight: 257 KB
• Volume: 26
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)98651-9

✦ Synopsis

Asymmetric inductive effects have been measured on the Diels-Alder reaction of dimethyl fumarate with o-quinodimethane bearing a chiral u-alkoxy group. The chiral substituents used were f-phenylethoxy, 2-(1-phenyl)propoxy, 1-(2_phenyl)propoxy, 2-(4-phenyljbutoxy and l-cyclohexylethoxy. The greatest asymmetric induction was found with the first of these chiral substituents (47% ee). A r-stacking effect, previously suggested as the rationale for asymmetric induction in a similar system, is shown to be inconsistent with the results from this study, While there have been several studies on asymmetric Diels-Alder reactions of dienes (1,2), there have been more limited studies on o-quinodimethanes CO-QDMs) (3)(4)(5)(6). Earlier studies focussed on intramolecular reactions and the asymmetric synthesis of steroids (3). More recently there have been two studies on asymmetric induction in intermolecular additions (5,6).

A study by Ito and coworkers is unique in that it uses a chiral substituent in the o-QDM rather than in the dienophile to control the cycloaddition (5).