Dimethylaminopyridine analogs

A second example of latent biphasic catalysis used the polymer-bound trifunctional base catalyst 129 as a dimethylaminopyridine analog in acylation of 2,6-dialkylphenols by (Boc)20 in a 1 1 heptane-ethanol solvent mixture. After acylation of the phenol was complete, the addition of 10 vol% H2O perturbed the system. The yields of product carbonate from Eq. 66 were 35,66,89,99%, 99, and 99% through the first six cycles. 

A second example of latent biphasic catalysis used the polymer-bound trifunctional base catalyst 129 as a dimethylaminopyridine analog in acylation of... 

Reaction of N,N-dimethylaniline with 1-cyanobenziodoxol 1783 to afford N-methyl-N-cyanomethylaniline 1784 in 97% yield has been discussed in Section 12.1 [31]. Analogously, oxidation of dimethylaniline with iodosobenzene and trimethylsilyl azide 19 at 0°C in CDCI3 gives the azido compound 2040 in 95% yield, iodobenzene, and HMDSO 7 [194, 195] (Scheme 12.56). Likewise, the nucleophilic catalyst 4-dimethylaminopyridine (DMAP) is oxidized, in 95% yield, to the azide 2041, which is too sensitive toward hydrolysis to 4-N-methylaminopyri-dine to enable isolation [194, 195]. Amides such as 2042, in combination with tri-... 

Having proved the synthetic utility of their system, the authors subsequently evaluated a second supported base, 4-dimethylaminopyridine (AO-DMAP) 118, toward the acylation of 2° alcohols (Scheme 30). Employing a premixed solution of phenyl-l-ethanol 119, Et3N 14 and acetic anhydride 37 (0.33, 0.50, and 0.50 M) in hexane, reactions were conducted at room temperature and the effect of residence time evaluated (10-50 s). Using a 60 cm packed bed, the authors were able to obtain near quantitative conversions to 120 employing residence times <20 s, with flow reactions providing superior results to those obtained in analogous batch reactions. 

The basic nucleophilic poly(iV-alkylacrylamide)-immobilized catalyst 95 was prepared from the active estercopolymer 94 according to the chemistry shown in Eq. 37 [131]. This polymercontained a ca. 8 mol% loading of an analog of ATjAT-dimethylaminopyridine, anucleophilic catalyst that others had immobilized on insoluble cross-linked resins previously. This soluble version was shown to be effective as a catalyst for acylation of hindered alcohols and phenols (Eqs. 38 and 39). This catalyst contained an azo dye as a marker, which facilitated analysis of the phase separation of the polymer-immobilized catalyst. 

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