P-Aminobenzyl alcohol

As with the other aminoplastics, the chemistry of resin formation is incompletely understood. It is, however, believed that under acid conditions at aniline-formaldehyde ratios of about 1 1.2, which are similar to those used in practice, the reaction proceeds via p-aminobenzyl alcohol with subsequent condensation between amino and hydroxyl groups (Figure 24.10). 

Alkyl Groups. As expected, all three toluidines give toluenearsonic acids in good yields (45-55%). From the o-, m-, and p-aminobenzyl alcohols the corresponding arsonic adds result in yields of 12-20%.2S When the reaction is applied to 2-hydroxy-4-mtro-5-alkylanilines,24 the yield of arsonic acid decreases as the length of the side chain is increased. o-Butylphenylarsonic acid is obtained by the Bart method in only a 12% yield.26 "... 

Figure 11.5. Prodrug of paclitaxel with two p-aminobenzyl alcohol moieties.

In the presence of acid, the amino group of aniline is protected and formaldehyde is directed to the p-position to give the hydrochloride of p-aminobenzyl alcohol. Treatment with alkali gives the free base which polymerizes, possibly as follows ... 

These reactions are illustrated with the fragmentation of two isomeric aminoalco-hols and one aminodiol, which have been observed upon thioindigo sensitized irradiation in benzene solution [203]. Under these conditions, the (p-N,N-dimethyl-aminobenzyl) benzyl alcohol (24) suffers fragmentation with apparent internal disproportionation the benzyl alcohol function is oxidized, whereas the p-aminobenzyl function is reduced, giving rise to iVJV-dimethyl-p-toluidine and benzaldehyde. The acceptor is involved only as a sensitizer and, hence, remains unchanged. 

Other spacers such as ethylene diamine, o-aminobenzyl alcohol, p-hydroxylben-zyl alcohol, and o-hydroxylbenzyl alcohol have also been utilized. The application of some of these spacers will be illustrated in the examples presented later. 

Katritzky and Harris reported in 1992 the use of diethylzinc for the chiral amino alcohol-mediated enantioselective addition to the C=N bond in these compounds (Scheme 12) [34]. These substrates act as masked activated N-acylimines. Of the large variety of Hgands available for the catalytic asymmetric reactions of dialkylzinc reagents,the sterically constrained P-dialkylamino alcohol, (-)-N,N-dibutylnorephedrine (DBNE) 18, prepared by alkylation of commercially available norephedrine, was selected for this study. Some preliminary experiments conducted with the use of -(aminobenzyl)benzotriazoles gave the ethylated product, but with no enantioselectivity. Diethylzinc (Et2Zn) was found to react even in the absence of a chiral promoter. The behavior of the less reactive N-(amidobenzyl)benzotriazoles 19a-g was then investigated. 

Anthranilic acid to o-aminobenzyl alcohol P/C BASF Beck et al. (1985)... 

Recently, Phan et al. (2013) prepared an open metal site MOF Cu(BDC) and successfully applied it to the modified Friedlander reaction. In the presence of 3-5 mol% Cu(BDC), several 2-aryl quinolines were efficiently synthesized from 2-aminobenzyl alcohol and methyl ketones (Scheme 4.42). Different from the previous reports, the reaction of p-methoxyacetophenone or p-nitroacetophenone did not occur in this catalytic system. 

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