Amines condensation with benzaldehydes

The chiral dipolarophiles of Garners and Dogan, which were derived from Oppolzer s sultam, have been previously discussed in Section 3.2.1 and, in an extension to these results, the sultam moiety was used as the stereodirecting unit in enantiopure azomethine ylides (56). The ylides were generated either by thermo-lytic opening of N-substituted aziridines or by the condensation of the amine functionality with benzaldehyde followed by tautomerism. These precursors were derived from the known (+)-A-propenoylbornane-2,10-sultam. Subsequent trapping of the ylides with A-phenylmaleimide furnished the cycloaddition products shown in Schemes 3.60 and 3.61. 

Compound (408), which was prepared by the condensation of the amine (407) with benzaldehyde in the presence of piperidine, upon treatment with phenylhydrazine afforded the orange pyrazolo[3,4-6]pyridin-2-one (410) (69%) (Scheme 45) <9iPS(63)ll9>. The structure (410) was confirmed by an alternative synthesis involving a reversal of the reactants. In this case compound (407) was initially reacted with phenylhydrazine to give compound (409) and subsequent condensation with benzaldehyde gave the product (410). 

Upon treatment with hydroxylamine mesembrine gave an oxime, isolated as a crystalline hydrochloride (6). This ketoxime was reduced with lithium aluminum hydride to a primary amine 9). By catalytic hydrogenation mesembrine yields an optically active alcohol, mesem-brinol (6, 7). Condensation with benzaldehyde formed a dibenzylidene derivative of mesembrine (9). 

For some time considerable confusion existed as to whether the salt or the anhydride condensed with the aldehyde,9 10 for when benzaldehyde was heated with acetic anhydride and sodium butyrate, ethylcinnamic acid was found to be the main product.11 It is now quite clear, however, that it is the anhydride which undergoes condensation and that the sodium salt is simply the strongest commonly used base that will not destroy the anhydride. Thus acetic anhydride will condense with benzaldehyde in the presence of pyridine or triethyl amine whereas benzaldehyde, sodium acetate, and pyridine will not undergo the same reaction.12 When an acid salt different from the anhydride is employed, an equilibrium... 

FIGURE 5.3 Initial primary amines condensed with 2-(2-bromoethyl)benzaldehyde (11) to form iminium salts. 

One of the first uses of directed metalation as a route to heterocycles was the synthesis of phthalans (2,3-benzo-l,4-dihydrofurans) by the thermally induced cyclization of the methiodides of ortho-substituted di-methylbenzylamines (Reaction 37) (45). The amine was lithiated in the ortho position by n-butyllithium and condensed with benzaldehyde and benzophenone. The corresponding alcohols obtained upon aqueous work-up were converted to their respective methiodides. Heating the methiodides to 200°C for one hour under nitrogen gave the phthalans... 

Direct replacement of an amino group by hydrogen is possible only in certain cases. Such reductive fissions are particularly well known for tertiary amines and quaternary ammonium compounds and occur especially readily with allyl- and benzyl-substituted amines. In the last-mentioned cases the benzyl group is removed as toluene, and this reaction route is used for preparation of secondary from primary aliphatic amines the primary amine is first condensed with benzaldehyde, and the resulting Schiff base is reduced to the alkylbenzylamine this is converted by alkylation into the dialkylbenzyl-amine, from which finally the benzyl group is removed by catalytic hydrogenation 544... 

Aldehydes undergo condensation with primary amines with the elimination of water to give compounds known as SchifF s Bases, which can also be used to characterise aldehydes. Benzaldehyde for example condenses readily with... 

Benzal derivatives. Primary aromatic amines generally condense directly with benzaldehyde to form benzal derivatives (Schiff s bases or anils) ... 

Triamterene (31) is a diuretic that has found acceptance because it results in enhanced sodium ion excretion without serious loss of potassium ion or significant uric acid retention. Tautomerism of aminopyrimidines (e.g., 27a and 27b) serves to make the "nonenolized" amine at the 5 position more basic than the remaining amines. Thus, condensation of 27 with benzaldehyde goes at the most basic nitrogen to form 28. Addition of hydrogen cyanide gives the a-aminonitrile (29). Treatment of that intermediate with base leads to the eyelized dihydropirazine compound (30). This undergoes spontaneous air oxidation to afford triamterene (31). ... 

With dimethyl(trimethylsilyl)amine, the nickel enolate 162 is capable of reacting with benzaldehyde to produce the condensation product 163 (Scheme 60). 

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