Abstract
Reaction of 2-(4′-bromobutyl)-5-ethoxyoxazole (1) with nucleophiles led either to SN2 substitution products or to products with a piperidine skeleton. The latter were shown to arise from an intramolecular ring closure to an oxazolium salt 7, which was faster in the presence of a catalytic amount of NaI and in a polar solvent and for which NMR evidence is presented. The further transformation of 7 to 3–6 apparently involves addition of nucelophiles to 7 to produce 4-oxazoline 8 which opens to azomethine ylide 9. Neutralization of the latter occurred either via a proton shift, an alkyl shift, or via trapping by a dipolarophile (electron poor or electron rich). FMO calculations explain the preferred regiochemistry observed during trapping of ylide 9b.
Original language | English |
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Pages (from-to) | 3070-3075 |
Number of pages | 6 |
Journal | Journal of Organic Chemistry |
Volume | 57 |
Issue number | 11 |
DOIs | |
State | Published - 1 May 1992 |