TV-Acyliminium ion

Decahydroquinoline Alkaloids.—A review on the total synthesis of lycopodium alkaloids has appeared it includes syntheses of luciduline.25 Additional total syntheses of ( )-gephyrotoxin26 and ( )-perhydrogephyrotoxin27 have been described, and ( )-depentylperhydrogephyrotoxin has been synthesized via an interesting cyclization of a vinylogous TV-acyliminium ion.28... 

The structures of the 2-oxazolinium, 1,3,5-oxadiazinium and 3-azapyrylium salts obtained by means of electrophilic catalysis by acylium ions102,113 point to the fact that their formation proceeds not via Af,7V-bis-acyliminium ions 332 and 333, but via the TV-acyliminium ions 322 (i.e. those protonated at the nitrogen atom). In our opinion142, the acetoxy azaallenium ions 335 can be transformed to the Af-acyliminium cations 337 by a deacylation to the N-acylimines 336, followed by protonation of the latter (equation 91). Such a process is quite possible under the conditions used for... 

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