ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Synthetic Application of Epoxynitrones I. Nitrone, a New α-Methylidene-γ-lactone Annelating ReagentThe N-(2, 3-epoxypropyliden)-cyclohexylamine-N-oxide/CF3SO3SiR3 reagent descried in this communication opens a new and interesting entry to the versatile N-substituted N-propenylnitrosonium ions of type b (Scheme 6). One of the uses of this reagent is shown to be the synthesis of α-methylidene-γ-lactones from olefins. This new method shows similar features as the method based on 2, 3-dichloropropylidenamine-oxide/AgBF4 originally developed for the same purpose by Petrzilka, Felix and Eschenmoser.Epoxynitrone 18 can be transformed to the positively charged heterodiene of type b (Scheme 5) using the highly electrophilic reagents CF3SO3SiMe3 (23) and CF3SO3Si (t-Bu)Me2 (24), respectively. Low temperature 1H- and 13C-NMR. spectroscopy at -78° showed the sole formation of the nitrone-O-silyl-ethers a (Scheme 5). Epoxid opening leading to the diene b and subsequent reactions are observed only at about -30°. The diene b prepared in situ, adds to isolated double bonds by way of an inverse Diels-Alder reaction to afford cycloadducts of type 27 (Scheme 7). Their stable cyanoderivatives, e.g. 28 (Scheme 7), can be isolated and transformed via 31, 44 and 54 into cis annelated α-methylidene-γ-lactones of type 55 (Scheme 11). Using trisubstituted olefins, substitution at the lower substituted olefinic C-atom competes efficiently with the cycloaddition (e.g. 34, Scheme 8).
Additional Material:
8 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19790620129
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