Is There Stereoelectronic Control in Hydrolysis of Cyclic Guanidinium Ions?

• Published in: Journal of the American Chemical Society Vol. 123; no. 19; pp. 4446 - 4450
• Main Authors: Perrin, Charles L, Young, David B
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 16-05-2001
• Subjects: Guanidine - chemistry; Hydrolysis; Magnetic Resonance Spectroscopy; Stereoisomerism; Urea - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja003672y

To assess stereoelectronic effects in the cleavage of tetrahedral intermediates, a series of five-, six-, and seven-membered cyclic guanidinium salts was synthesized. If stereoelectronic control by antiperiplanar lone pairs is operative, these are expected to hydrolyze with endocyclic C−N cleavage to acyclic ureas. However, hydrolysis in basic media produces mixtures of cyclic and acyclic products, as determined by 1H NMR analysis. The results show that in the six-membered ring antiperiplanar lone pairs provide a weak acceleration of the breakdown of the tetrahedral intermediate, but in five- and seven-membered rings there is no evidence for such acceleration, which instead can be provided by syn lone pairs.