Iminium ions, as intermediates

Tropinone is a structural component of several alkaloids, including atropine. The synthesis is based on a double Mannich process with iminium ions as intermediates. The Mannich reaction in itself is a three-component domino process, which is one of the first domino reactions developed by humankind. 

Triazines of type 3 are also accessible by an add-catalyzed cydoconden-sation of imido- esters with elimination of alcohol (see (1)). Combination of three imidoester units (functioning as activated nitriles) probably takes place by an dectrophilic addition-ehmination mechanism involving iminium ions as intermediates. 

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See also in sourсe #XX -- [ ]

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