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Deamination Reactions, 48. - Decomposition of 5- and 6-Alkoxy-2-norbornanediazonium Ions
Kirmse, Wolfgang,Siegfried, Rainer,Feldmann, Georg,Schoen, Sabine,Schwarz, Johannes
, p. 477 - 484 (2007/10/02)
The aim of the present investigation was to probe the effect of 5- and 6-alkoxy substituents on the Wagner-Meerwein rearrangement of 2-norbornyl cations.The cations were generated by decomposition of the analogous diazonium ions since 6-methoxy-2-norbornyl tosylates are known to react with complete fragmentation.With the exception of 38, all 6-alkoxy-2-norbornane-diazonium ions gave acceptable yields of exo alcohols in addition to fragmentation products.These exo alcohols were formed without Wagner-Meerwein rearrangement, as indicated by the distribution of isomers or deuterium labels. 6,6-Dimethoxy-2-norbornanediazonium ions (27) showed an additional endo-6,2-OCH3 shift which was not observed with the endo-6-methoxy species 20b.In contrast, the Wagner-Meerwein rearrangement was virtually unaffected by 5-alkoxy substituents.We assume that alkoxy groups at C-6 destabilize the bridged structure of 2-norbornyl cations, as suggested by ab-inito calculations on protonated cyclopropanes.
