A new access to pyrrolizidine derivatives: Ring contraction of methyl (E)-[1, 2-oxazin-3-yl] propenoates

R Zimmer, M Collas, R Czerwonka, U Hain…

Index: Zimmer, Reinhold; Collas, Markus; Czerwonka, Regina; Hain, Ute; Reissig, Hans-Ulrich Synthesis, 2008 , # 2 p. 237 - 244

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Citation Number: 19

Abstract

Abstract Nitrosoalkene 2 generated in situ from oxime 3 underwent smooth hetero Diels- Alder reaction with enol ethers 1 to afford 1, 2-oxazine derivatives 4 bearing an exocyclic C= C bond. Methoxyallene 8 and 2 provided 6H-1, 2-oxazine 10 in good overall yield. The exocyclic double bond of this type of 1, 2-oxazines can be employed for addition reactions as demonstrated by dihydroxylation of 4a with potassium permanganate, smoothly ...