Ami nal

An alternative route to tertiary allyl- and propargylamines 145 and 146 is the reaction of Grignard compounds with iminium triflates 147 and 148 (equations 77 and 78). The intermediate iminium triflates 147 and 148 are obtained from the corresponding ami-nals by reaction with Tf20. Primary propargylamines can be prepared from tetraallylated aminals °. 

Now the terminal amino group is methylated by SAM and the secondary amine cyclizes on to the pyridoxal imine to give an ami-nal. Decomposition of the aminal the other way round expels pyridoxamine and releases the salt of an electrophilic imine. 

The rapid MW-assisted synthesis of bridgehead nitrogen heterocycdes has heen achieved under solvent-free conditions as exemplified by the synthesis of pyrimi-dino[l,6-a]benzimidazoles [135] and 2,3-dihydroimidazo[l,2-c]pyrimidines [136] from N-acylimidates and activated 2-benzimidazoles or imidazoline ketene ami-nals respectively (Scheme 2.2-46). 

In conclusion, we express our gratitude to Professor G. Albert Hill for reading our manuscript and for his advice and encouragement, to Miss Amy F. Meserve for her assistance in the preparation of the manuscript, to Dean William C. White for his interest, and to the editors of the Journal of Chemical Edumtion, the Jowr-nal of the American Chemical Society, and Chemical Remews for their permission to use material first published in their journals. 

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