Manolova Y, Kurteva V, Antonov L, Marciniak H, Lochbrunner S, Crochet A, Fromm K M, Kamounah F S, Hansen P E
Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G.Bonchev str., bldg. 9, Sofia 1113, Bulgaria.
Phys Chem Chem Phys. 2015 Apr 21;17(15):10238-49. doi: 10.1039/c5cp00870k.
A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism. In the case of 4-hydroxy-1-naphthaldehyde concentration dependent deprotonation has been detected in methanol and acetonitrile. For 4-hydroxy-3-(piperidin-1-ylmethyl)-1-naphthaldehyde (a Mannich base) an intramolecular proton transfer involving the OH group and the piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer.
通过紫外可见光谱、核磁共振和理论方法对一系列萘醛（包括一种曼尼希碱）进行了研究，以探索它们潜在的互变异构现象。在4-羟基-1-萘醛的情况下，已在甲醇和乙腈中检测到浓度依赖性去质子化。对于4-羟基-3-（哌啶-1-基甲基）-1-萘醛（一种曼尼希碱），发生了涉及羟基和哌啶氮的分子内质子转移。在乙腈中，平衡主要处于羟基形式，而在甲醇中，质子转移的互变异构体是首选形式。在氯仿和甲苯中，羟基形式完全占主导。4-羟基-1-萘醛和4-甲氧基-1-萘醛（固定烯醇形式）在研究的溶剂中均显示出二聚化，并且为后者获得的晶体学数据证实了环状二聚体的存在。
