Effect of configuration of 2-vinyldiazocarbonyl compounds on their reactivity: experimental and computational study

• Published in: Organic & biomolecular chemistry Vol. 12; no. 4; pp. 682 - 689
• Main Authors: Supurgibekov, Murat B., Cantillo, David, Kappe, C. Oliver, Prakash, G. K. Surya, Nikolaev, Valerij A.
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 28.01.2014
• Subjects: Azo Compounds - chemistry; Chemistry; Chemistry, Organic; Molecular Structure; Physical Sciences; Pyrazoles - chemical synthesis; Pyrazoles - chemistry; Quantum Theory; Science & Technology; Vinyl Compounds - chemistry; PYRAZOLES; DIELS-ALDER REACTIONS; LIGANDS; WITTIG REACTION; STEREOCHEMISTRY; CHEMISTRY; COORDINATION; VINYLDIAZOCARBONYL COMPOUNDS
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c3ob42102c

Non-fluorinated vinyldiazo compounds with trans-configuration irrespective of the nature of 3-R-1-substituent (R-1 = H, Me, TBSO) even under ambient conditions easily cyclize to produce pyrazoles, while cis-stereoisomers undergo similar ring closure only at elevated temperatures or decompose to produce vinyloxocarbene reaction products. The 3-CF3-substituted analogues with cis- or trans-configuration do not produce pyrazoles at all, but on heating furnish only vinylcarbene derived products. DFT calculations of theoretical energy barriers adequately explain the different experimental reactivity found for stereo-isomeric vinyldiazocarbonyl compounds, and a new model for their interconversion through the corresponding pyrazoles has been suggested.