Molecular Recognition between Chemically Modified β-Cyclodextrin and Dec-1-ene: New Prospects for Biphasic Hydroformylation of Water-Insoluble Olefins
✍ Scribed by Dr. Eric Monflier; Dipl.-Chem. Georges Fremy; Prof. Dr. Yves Castanet; Prof. Dr. André Mortreux
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 372 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0044-8249
No coin nor oath required. For personal study only.
✦ Synopsis
was distinctly different from the spectrum of 2-H". Under preparative conditions, the photolysis of 2-H with tetranitromethane in HFP at 2 0 ' C gave after 2 h a 19% (after 4 h, 33 YO) conversion into 1,4-dimethoxy-2-nitrobenzene (2-NO,) as the only product; the analogous reaction in dichloromethane gave under identical conditions a 47 YO (after 4 h, 82 O h ) conversion into 2 -N 0 2 . Since the product in the two solvents is the same, one can only conclude that the higher efficiency of the conversion in dichloromethane points to a trinitromethanide ion initiated pathway, possibly leading to a transient adduct.I4] which is eventually transformed into 2-N02. The markedly lower efficiency i n HFP would then be caused by H F P blocking this pathway. leaving the fairly slow reaction between 2-H" and NO, as ;I fcasible route to 2-NO2.
1.4-Dimethylnaphthalene (3). which gave no EPR signal upon photolysis with tetranitromethane in dichloromethane at -60 'C."''] in H F P under the same conditions but at 5 "C gave a broad unresolved signal. A preparative run in H F P ([3] = 0.5, [tetranitromethane] = 1.0 moldm-3) at 20°C after 40% conversion showed essentially quantitative formation of 1,4dimethyl-7-nitro-naphthalene. Again it is evident that the formation of the 3"+-trinitromethanide ion derived products obtained i n dichloromethane at 20' C,IS1 namely the adducts 4 and 5 (in total 49 YO yield) and the side chain nitro substitution product 6 (48 '!A), have been completely suppressed. 3 4 5 6
These examples demonstrate the unique high persistency of radical cations in HFP, which allows these radical cations to be observed in the presence of a nucleophile such as trinitromethanide ion even at room temperature. The reactivity of the radical cations that remain leads to dehydrodimer formation and:or radical coupling with NO, to give the "normal" product(s) of the reactions of ArH" with NO,. Thus it appears that HFP will discriminate decisively between the radical and electrophilic reactivity of radical cations.