Scalar Coupling between the15N Centres in Methylated 1,8-Diaminonaphthalenes and 1,6-Diazacyclodecane: To What Extent is2HJNN a Reliable Indicator of NN Distance?
作者:Guy C. Lloyd-Jones、Jeremy N. Harvey、Paul Hodgson、Martin Murray、Robert L. Woodward
DOI:10.1002/chem.200304890
日期:2003.9.22
in the protonated series as the degree of methylation increases. The effect in the free-base forms is much less pronounced (2.9 to 3.7 Hz) with no scalar N,N coupling detected in the permethylated compound (proton sponge) due to the lack of hydrogen bond between the N,N centres. Neither the pK(a) nor the N-N distance in the protonated forms correlates with (2H)J(NN). However, the sum of the (13)C NMR
氢键氮中心((2H)J(NN))的游离碱和质子化形式的[(15)N(2)]-N-甲基化1,8-二氨基萘的完整系列之间的标量偶合已直接(15N [1H] NMR)或间接(13C [1H] NMR)确定了[D(7)] DMF溶液,并模拟了ABX光谱的X部分(X = 13C,A,B = 15N))。此外,间接通过13C [(1H]]测定了[(15)N(2)]-1,6-二甲基-1,6-二氮杂环癸烷的HBF(4)盐中的(2H)J(NN)值NMR光谱学。经DFT计算并参考CSD证实,除了全甲基化化合物的游离碱,萘骨架的刚性导致每个系列中N,N距离或HN,N角的偏差很小。质子海绵),其中萘环严重变形以减轻应变。尽管有这些限制,但随着甲基化程度的增加,(2H)J(NN)值在质子化序列中从1.5 Hz平稳增加到8.5 Hz。由于在N,N中心之间缺乏氢键,因此在全甲基化化合物(质子海绵)中未检测到标量N,N偶联,游离碱形式的效应就不那么明显(2