A novel borane effect on the C/O alkylation ratio in competing SRN1–SN2 reactions
✍ Scribed by Ana Shifman; Milon Sprecher; Shmaryahu Hoz
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 88 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
The presence of Et 3 B in the reaction of 2-nitropropane anion (1) with p-nitrobenzyl bromide (5b) in tert-butyl alcohol results in an approximately three-fold increase in C-alkylation [yielding 1-(2-methyl-2nitropropyl)-4-nitrobenzene ( 9) by an S RN 1 mechanism] versus O-alkylation (by an S N 2 mechanism, and leading thereafter to p-nitrobenzaldehyde). Dioxygen completely inhibits C-alkylation in the absence of Et 3 B, but is ineffective in its presence. p-Dinitrobenzene does not significantly affect the thermal reaction (30 °C) of 1 with 5b, but partially inhibits C-alkylation in reaction under photostimulation. However, p-dinitrobenzene catalyzes C-alkylation in the thermal reaction in the presence of Et 3 B. Rationalizations of these novel results are presented. Qualitatively similar results were obtained for the reaction of phenylnitromethane anion (16) with 5b.