From amines and aldehydes

In a 500 ml. flask, fitted with a reflux condenser, place 53 g. of 1-chloro-methylnaphthalene (Section IV.23), 84 g, of hexamethylenetetramine and 250 ml. of 1 1 acetic acid [CAUTION 1-Chloromethylnaphtha-lene and, to a lesser degree, a-naphthaldehyde have lachrymatory and vesicant properties adequate precautions should therefore be taken to avoid contact with these substances.] Heat the mixture under reflux for 2 hours it becomes homogeneous after about 15 minutes and then an oil commences to separate. Add 100 ml. of concentrated hydrochloric acid and reflux for a further 15 minutes this will hydrolyse any SchifiF s bases which may be formed from amine and aldehyde present and will also convert any amines into the ether-insoluble hydrochlorides. Cool, and extract the mixture with 150 ml. of ether. Wash the ether layer with three 50 ml. portions of water, then cautiously with 50 ml. of 10 per cent, sodium carbonate solution, followed by 50 ml. of water. Dry the ethereal solution with anhydrous magnesium sulphate, remove the ether by distillation on a steam bath, and distil the residue under reduced pressure. Collect the a-naphthaldehyde at 160-162718 mm. the yield is 38 g. 

Imines are readily formed from amines and aldehydes or ketones under physiological conditions. In addition, they are readily hydrolyzed back to the amine and the carbonyl compound. These properties provide a common way in biochemical reactions to temporarily link an aldehyde or a ketone to a protein by reacting the carbonyl with a free amino group of the protein to form an imine. 

M-K. Wong, L-M. Ho, Y-S. Zheng, C-Y. Ho, D. Yang, Asymmetric epoxidation of olefins catalyzed by chiral iminium salts generated in situ from amines and aldehydes, Org. Lett. 3 (2001) 2587. 

Aryl or heteroaryl 1,2,4-trioxanes have been prepared in variable yields from amines and aldehydes by autoxidation of the in j/tw-formed imine and reaction of the resulting hydroperoxide with excess aldehyde (Scheme 29) [60], This one-pot sequence provides the 1,2,4-trioxanes as diastereomeric mixtures with the cw-isomer predominating [60bj. 

This route depends on the samarium-catalysed aldol-type condensation of nitroalkanes with imines generated from amines and aldehydes, all three components being... 

Azomethines from amines and aldehydes Selective furan ring hydrogenation and opening... 

Potassium permanganate Benzimidazo[l,2-c]quinazolines Azomethines from amines and aldehydes... 

Imine Formation from Amines and Aldehydes or Ketones... 

The next important class comprises non-isocyanide-based MCRs. In contrast to IMCRs, non-isocyanide-based MCRs do not rely on the unique properties of isocyanides, but rather rely in most cases on the reactivity of imines generated in situ from amines and aldehydes. This class includes the Gewald reaction [4], the Hantzsch reaction [6], the Biginelli reaction [3], the Petasis reaction [47 9], the Kabachnik-Fields reaction [8, 9], the Povarov reaction [50], and the Doebner reaction [51]. 

In the mid 1990s Petasis reported three-component coupling reactions of boronic acids, amines, and aldehydes as a general approach to optically active secondary amines. Alkenyl boronic acids were shown conveniently to undergo addition to iminium ions formed in situ under mild conditions from amines and aldehydes (Scheme 11.9) [65]. For example, a mixture consisting of vinylboronic acid 64, (S)-2-phenylglycinol (65), and aldehyde 66 furnishes 67 in 78 % yield and >99 1 dr. 

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