Pyridin-2-yl Guanidine Derivatives: Conformational Control Induced by Intramolecular Hydrogen-Bonding Interactions

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• 作者：Brendan Kelly ; Daniel H. O'Donovan ; John O'Brien ; Thomas McCabe ; Fernando Blanco ; Isabel Rozas
• 刊名：Journal of Organic Chemistry
• 出版年：2011
• 出版时间：November 18, 2011
• 年：2011
• 卷：76
• 期：22
• 页码：9216-9227
• 全文大小：510K
• 年卷期：v.76,no.22(November 18, 2011)
• ISSN：1520-6904

文摘

The synthesis and conformational analysis of a series of pyridin-2-yl guanidine derivatives using NMR, X-ray crystallography, and B3LYP/6-31+G** theoretical studies are reported. A remarkable difference was observed in the ¹H NMR spectra of the guanidinium salts as compared with their N,N鈥?di-Boc protected and neutral analogues. This difference corresponds to a 180掳 change in the dihedral angle between the guanidine/ium moiety and the pyridine ring in the salts as compared to the Boc-protected derivatives, a conclusion that was supported by theoretical studies, X-ray data, and NMR analysis. Moreover, our data sustain the existence of two intramolecular hydrogen-bonding systems: (i) between the pyridine N1 atom and the guanidinium protons in the salts and (ii) within the tert-butyl carbamate groups of the Boc-protected derivatives. To verify that the observed conformational control arises from these intramolecular interactions, a new series of N-Boc-N鈥?propyl-substituted pyridin-2-yl guanidines were also prepared and studied.