Structure and Photochemistry of a Saccharyl Thiotetrazole


Ismael A., Borba A., Henriques M. S. C., Paixao J. A., Fausto R., Cristiano M. L. S.

JOURNAL OF ORGANIC CHEMISTRY, vol.80, no.1, pp.392-400, 2014 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 80 Issue: 1
  • Publication Date: 2014
  • Doi Number: 10.1021/jo502419u
  • Journal Name: JOURNAL OF ORGANIC CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Index Chemicus (IC)
  • Page Numbers: pp.392-400
  • Istanbul Kültür University Affiliated: Yes

Abstract

The molecular structure and photochemistry of 5-thiosaccharyl-1-methyltetrazole (TSMT) were studied by means of matrix-isolation FTIR spectroscopy, X-ray crystallography, and theoretical calculations. The calculations predicted two conformers of TSMT that differ in energy by more than 15 kJ mol(-1). The infrared spectrum of TSMT isolated in solid argon was fully assigned on the basis of the spectrum calculated (O3LYP/6-311++G(3df,3pd)) for the most stable conformer. In the crystal, TSMT molecules were found to assume the same conformation as for the isolated molecule, with each molecule forming four hydrogen bonds with three neighboring molecules, leading to a network of TSMT oligomers. Upon UV (lambda = 265 nm) irradiation of the matrix-isolated TSMT, two photodegradation pathways were observed, both arising from cleavage of the tetrazolyl ring. Pathway a involves cleavage of the N-1-N-2 and N-3-N-4 bonds with extrusion of N-2, leading to photostable diazirine and thiocarbodiimide derivatives. The photostability of the photoproduced diazirine under the conditions used precluded its rearrangement to the nitrile imine, as reported for 5-phenyltetrazole by Begue et al. ( J. Am. Chem. Soc. 2012, 134, 5339). Pathway b involves cleavage of the C-5-N-1 and N-4-N-3 bonds, leading to a thiocyanate and methyl azide, the latter undergoing subsequent fragmentation to give CNH.