Heterocyclic products of oxidative triflamidation of unsaturated compounds: gas-phase vs. crystal structure

Abstract

A gas-phase electron diffraction analysis combined with mass-spectrometry (GED/MS) of (2R,9S)-trans-2,9-diiodo-13-(triflyl)-13-azabicyclo[8.2.1]tridec-5-ene 5 was performed and the results compared with the earlier studied by GED/MS and X-ray analysis triflamide derivatives, that is 3,7,9-tris(triflyl)-3,7,9-triazabicyclo[3.3.1]nonane 2, 6-iodo-3-(triflamidomethyl)-4-triflyl-1,4,2,7-oxazadisilepane 3, and2,2,4,4-tetramethyl-6,8-bis(triflyl)-3-oxa-6,8-diaza-2,4-disilabicyclo[3.2.2]nonane 4. In addition, the first GED study was performed for triflamide CF3SO2NH2, 6, for which the X-ray structure has also been studied. Two conformers of 5 with the oppositely distorted dihedral angles in the five-membered ring were proved in gas phase, and, after careful analysis, also in the crystal. Very low barrier to interconversion (1.7 kcal/mol) and energy difference (0.6 kcal/mol) were calculated. In gas, the S–N and S–C bonds are longer than in the crystal, clearly indicating tightening due to crystal packing effects.