Piperazines 2-aminoalcohols

Three acerands 48-50 show absorption maxima at ca. 400 nm in chloroform and turn blue on addition of amines. After many examinations of the complexation of the three acerands with large excess of various amines in alcohol and chloroform, it was found that COOH-dye 48 shows a marked blue shift (ca. 40 nm) of the absorption maximum by the addition of several diamines (piperazine, hydrazine, TMEDA = tetramethylethylenediamine), and two aminoalcohols in chloroform, in contrast to slight fluctuation of the maxima for amine complexes of the two references (Fig. 12). In other words, the yellow solution of 48 turns to blue with monoamine whereas to pink color with diamine, indicating very different coloration based on the two binding sites in the crown cavity. 

Additional catalysts have also been proposed for the reaction of Et2Zn with aromatic aldehydes, including (proline derivative 2.13 (R = CPh2OH) [110] and a four-membered analog [646], (1S,2R)-1.61 (R = S02Tol), 2.47, and pyridine-derived aminoalcohols [110, 644, 651, 1173]. Other catalysts include sulfur derivatives of ephedra alkaloids [645, 728], the Li diamide of piperazine 2.46, diamines 1.64 (R = 2-Py) and other related 2-aminopyridines [367, 648, 649, 1174], p-Hydroxysulfoximines have also been used as catalysts in these reactions [1175], as has an oxazaborolidine derived from ephedrine [1176],... 

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