Desaminierungsreaktionen, 34 1) Diels‐Alder‐Reaktionen mit Methoxycyclopentadien, ein Weg zu 1‐Methoxynorbornan‐2‐diazonium‐Ionen

Deamination Reactions, 34 1) Diels‐Alder Reactions of Methoxycyclopentadiene, a Route to 1‐Methoxynorbornane‐2‐diazonium Ions A Mixture of 1‐ and 2 ‐methoxycyclopentadiene ( 7 , 8 ) was prepared in four steps from cyclopentadiene. Diels‐Alder reaction of 7 + 8 with methyl acrylate produces a mixture of adducts from which the 1‐methoxy isomers ( 9 , 11 ) were obtained by distillation. Separation by way of the iodo lactone 20 , hydrogenation, and Curtius degradation afforded endo ‐ and exo ‐1‐methoxy‐2‐norbornylamin ( 14 , 17 ) Nitrous acid deaminations of 14 yielded norpinan‐2‐one ( 21 ) and norbornan‐2‐one ( 22 ) in a 3:7 ratio whereas 17 gave 22 only. The results of the deamination reactions confirm the position of the methoxy groups and illustrate the superiority of diazonium precursors in the norborane → norpinane rearrangement.