Reversal of nitrone cycloaddition regioselectivity with electron-deficient dipolarophiles
β Scribed by Sims, Joyner.; Houk, K. N.
- Book ID
- 121442479
- Publisher
- American Chemical Society
- Year
- 1973
- Tongue
- English
- Weight
- 406 KB
- Volume
- 95
- Category
- Article
- ISSN
- 0002-7863
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π SIMILAR VOLUMES
## Abstract The regioβ and stereoselectivity of cycloadditions of the nitrone 1a and the chiral, sugarβderived nitrones 13a and 13b with 3β(propβ2βenoyl)β1,3βoxazolidinβ2βone (2) depends on the nature of the __Lewis__ acid catalyst used. Addition of __Lewis__ acid reverses the regioselectivity of t
haszrzdznes are proposed as zntenediates zn the photoznduced cycloaddztzons of electron defzczent nztrones to dzpohrophztes.
Cycloaddition mechanisms can be separated phenomenologically into three classes. (1) concerted, (2) stepwise--diradical intermediate, and (3) stepwise--zwitterionic intermediate.