Unusual spontaneous α→β isomerization of unsymmetrical benzoins. Products and their structure

Authors

  • Andrey A. Anishchenko Oles Honchar Dnipropetrovsk National University, Ukraine
  • Vasiliy G. Shtamburg Ukrainian State University of Chemical Technology, Ukraine
  • Viktor V. Shtamburg National Technical University «Kharkiv Polytechnic Institute», Ukraine
  • Vitaliy V. Volosyuk Oles Honchar Dnipropetrovsk National University, Ukraine
  • Remir G. Kostyanovskiy N. N. Semenov Institute of Chemical Physics RAS, Russian Federation

DOI:

https://doi.org/10.15421/081316

Keywords:

benzoins, arylglyoxals, isomerization

Abstract

The article describes reactions of a series of arylglyoxals with 2-methylfuran and
furfural N,N-dimethylhydrazone. These interactions lead selectively to unsymmetrical benzoins. It was found that some of the benzoins underwent spontaneous thermal α→β benzoin isomerization in situ. The rearrangement took place in the absence of bases, which could be explained by two structural factors: (a) the presence of a halogen atom in the para-position of the aryl moiety, and (b) the presence of the Me2NN=CH-substituent in the 5-position of the furan ring. The proposed mechanism of the thermal rearrangement starts with an intramolecular protonation of the carbonyl oxygen by the hydroxyl. This leads to the 1,2-hydride shift onto the carbonyl group, finally yielding β-benzoins. The S-isomer of 2-hydroxy-2-(4’’-chlorophenyl)-1-(5’-N,N-dimethylhydrazonylfuryl-2’)-ethanone-1 was isolated by crystallization, and its structure was confirmed by the X-ray crystallography.

Author Biographies

Andrey A. Anishchenko, Oles Honchar Dnipropetrovsk National University

Associate Professors of the Department of Organic Chemistry

Vitaliy V. Volosyuk, Oles Honchar Dnipropetrovsk National University

PhD Student of the Department of Organic Chemistry

References

Ivonin, S. P., Anishchenko, A. A., Samucha, A. V., Lapandin, А. V., Serduk, V. N., Pleshkova, A. P., Shtamburg, V. G. Arylfuraciloines. Visn. Dnipropetr. Univ.: Khim., 2000, no. 5, p. 27-32.

Ivonin, S. P., Lapandin, A. V., Anishchenko, A. A., Shtamburg, V. G. Reaction of Arylglyoxales with Electron-Rich Benzenes and pi-Excessive Heterocycles. Facile synthesis of Heteroaryl alpha-Aciloins. Synth. Commun., 2004, vol. 34, p. 451-461.

Ivonin, S. P., Lapandin, A. V., Anishchenko, A. A., Shtamburg, V. G. Mutual Influence of (Dimethylhydrazono)methyl group and alpha-Hydroxy Ketone Molecules in Hetaryl Analogues of unsymmetric Benzoines. Eur. J. Org. Chem., 2004, p. 4688-4693.

Buck, J. S., Ide, W. S. The Synthesis of Benzoins. Organic Reactions., Wiley : New York, 1949, vol. 4, p. 269-304.

Julian, P. L., Passler, W. The Thermal Interconversion of Mixed Benzoines. J. Am. Chem. Soc., 1932, vol. 54, p. 4756.

Sheldrick, G. Short history of SHELX. Acta Cryst., Sect. A, 2008, vol. 64, p. 112.

Van der Sluis, P., Spek, A. L. BYPASS: an effective method for the refinement of crystal structures containing disordered solvent regions. Acta Cryst., Sect A, 1990, vol. 46, p. 194-201.

Spek, A. L. J. Single-crystal structure validation with the program PLATON. Appl. Cryst., 2003, vol. 36, p. 7-13.

Published

2014-03-28