Pseudo bases alkylation

The third structural possibility, the formulation of the compounds as pseudo-bases (445) was eliminated in the case of the anhydro-bases derived from p /r-iV -alkyl-l-methyl-3,4-dihydro-j8-carbolinium salts on the basis of their ultraviolet absorption spectra. A structure such as 445 demands indole-type absorption (A jax 280 mp) which was not encountered in the spectra of the anhydro-bases under discussion. This is in accord with general experience. Pseudo-bases are generally found only when dehydration to anhydro-bases is structurally impossible Indole-type absorption was indeed found in the case of the product obtained by treatment of 3,4-dihydro-)3-carboline methiodide (452 R = H) with alkali.In acid solution this compound gave the expected absorption (A jax 355 mp). In alkaline solution, however, an indole-type absorption (A jax 285 mp) was observed. On this basis formulation of the product as a derivative of 2-formylindole (454) ( max 315 mp) was rejected. Although the indole-type absorption is in accord with the pseudo-base structure 453 (R = H), the elemental analysis and molecular weight were not compatible with this formulation and the product was regarded as a dimeric anhydro-base (455). 

The di-N-alkyl derivatives of 1,5- and 1,8-naphthyridine have significantly different properties. Diquaternary salt 99 is relatively stable in neutral solution, whereas 100 exists in equilibrium with its pseudo base (101). A similar pseudo base structure (103) has been identified in the 1,8-bridged compound (102). The 1,5-naphthyridine salt (99) is readily reduced by a one-electron transfer process to give a fairly stable green radical cation (104). 

Aliphatic pseudo bases, e.g., 19 20 (R = R = R" = Me), are much less stable they are colorless water-soluble liquids which resinify rapidly in the air. For their preparation, barium carbonate can be replaced by sodium carbonate, sodium hydrogen carbonate, or sodium acetate.32,39 Alkyl-aryl derivatives are also unstable, because in these cases anhydro bases are also formed and the possibilities for aldol condensations or polymerizations are greatly increased. 

The third structural possibility, the formulation of the compounds as pseudo-bases (445) was eliminated in the case of the anhydro-bases derived from yr-JV-alkyl-l-methyl-3,4-dihydro-jS-carbolinium salts on the basis of their ultraviolet absorption spectra. A structure such as 445 demands indole-type absorption 280 mfi) which was not... 

A complicating feature of studies of carboxylic acid and their corresponding esters, having proximate keto or formyl groups, is the occurrence of ring-chain tautomerism, as in Scheme 1 (Valters and Flitsch, 1985). The rates of conversion of the ring and chain acids ([1] and [2] R = H) are rapid. However, both the pseudo and normal esters ([1] and [2], R = alkyl or aryl) can be isolated in favourable circumstances. The latter esters can also be interconverted by base- or acid-catalysis under suitable conditions. 

Schnee, V. R, Baker, G. A., Rank, E., and Ralmer, C. R, Electrokinetic chromatographic characterization of novel pseudo-phases based on N-alkyl-N-methyl-pyrrolidinium ionic liquid type surfactants. Electrophoresis, 2J, 4141-4148,2006. 

The ligand bis[(2-pyridyl)methyl]-l-(2-pyridyl)ethylamine (a-MeTPA, 2, R = Me) was first reported by Hojland et al.3 The method of preparation from 2-pyridylethylamine is similar to that for TPA. It was obtained also from TPA by reaction with a strong base followed by alkylation with Mel.6 It was recently prepared in enantiomerically pure form21 22 and it was shown that the ligand forms propeller-like complexes with Zn11 and Cu11 ions that have overall pseudo-C3 symmetry.21... 

A similar approach was reported by Lygo and co-workers who applied comparable anthracenylmethyl-based ammonium salts of type 26 in combination with 50% aqueous potassium hydroxide as a basic system at room temperature [26, 27a], Under these conditions the required O-alkylation at the alkaloid catalyst s hydroxyl group occurs in situ. The enantioselective alkylation reactions proceeded with somewhat lower enantioselectivity (up to 91% ee) compared with the results obtained with the Corey catalyst 25. The overall yields of esters of type 27 (obtained after imine hydrolysis) were in the range 40 to 86% [26]. A selected example is shown in Scheme 3.7. Because the pseudo-enantiomeric catalyst pairs 25 and 26 led to opposite enantiomers with comparable enantioselectivity, this procedure enables convenient access to both enantiomers. Recently, the Lygo group reported an in situ-preparation of the alkaloid-based phase transfer catalyst [27b] as well as the application of a new, highly effective phase-transfer catalyst derived from a-methyl-naphthylamine, which was found by screening of a catalyst library [27c],... 

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