38701-73-4Relevant academic research and scientific papers
RAMAN AND FAR-INFRARED SPECTRA OF GASEOUS 1,1,1,3,3,3-HEXAFLUORO-2-PROPANOL, CONFORMATIONAL STABILITY AND BARRIERS TO INTERNAL ROTATION
Durig, J. R.,Larsen, R. A.,Cox, F. O.,Veken, B. J. van der
, p. 183 - 202 (1988)
The Raman (4000-50 cm-1) and far-infrared (370-50 cm-1) spectra of gaseous 1,1,1,3,3,3-hexafluoro-2-propanol, (CF3)2CHOH, and of the O-D compound have been recorded.Particular attention is given to the O-H stretching and low frequency spectral regions, where evidence is found for the existence of both the trans and gauche conformers.From simulations of observed gas phase IR band profiles, it is possible to assign the O-H stretch at 3666 cm-1 to the gauche conformer and the one at 3626 cm-1 to the trans conformer (the O-H bond trans to the C-H bond).From relative intensities of the corresponding Raman lines as a function of temperature, the enthalpy difference in the gas phase is found to be 336+/-132 cm-1 (961+/-377 cal mol-1) with the trans conformer being more stable.The fundamental O-H torsion is observed at 331.7 cm-1 for the trans conformer and at 288.9 cm-1 for the gauche conformer with both bands being identified from their shift with deuteration.From these data an asymmetric potential function is calculated which gives a trans/gauche barrier of 937 cm-1 (2.68 kcal mol-1) and a gauche/gauche barrier of 360 cm-1 (1.00 kcal mol-1).One of the CF3 torsional modes has been observed at 90 cm-1 from which the barrier to internal rotation is estimated to be in the range and 5-6 kcal mol-1.All these data are compared to the corresponding quantities for some similar compounds.
Late-Stage β-C(sp3)-H Deuteration of Carboxylic Acids
Mal, Sourjya,Uttry, Alexander,Van Gemmeren, Manuel
supporting information, p. 10895 - 10901 (2021/08/03)
Carboxylic acids are highly abundant in bioactive molecules. In this study, we describe the late-stage β-C(sp3)-H deuteration of free carboxylic acids. On the basis of the finding that C-H activation with our catalysts is reversible, the de-deuteration process was first optimized. The resulting method uses ethylenediamine-based ligands and can be used to achieve the desired deuteration when using a deuterated solvent. The reported method allows for the functionalization of a wide range of free carboxylic acids with diverse substitution patterns, as well as the late-stage deuteration of bioactive molecules and related frameworks and enables the functionalization of nonactivated methylene β-C(sp3)-H bonds for the first time.
Scope and mechanism of a true organocatalytic beckmann rearrangement with a boronic acid/perfluoropinacol system under ambient conditions
Mo, Xiaobin,Morgan, Timothy D. R.,Ang, Hwee Ting,Hall, Dennis G.
supporting information, p. 5264 - 5271 (2018/04/24)
Catalytic activation of hydroxyl functionalities is of great interest for the production of pharmaceuticals and commodity chemicals. Here, 2-alkoxycarbonyl- and 2-phenoxycarbonyl-phenylboronic acid were identified as efficient catalysts for the direct and chemoselective activation of oxime N-OH bonds in the Beckmann rearrangement. This classical organic reaction provides a unique approach to prepare functionalized amide products that may be difficult to access using traditional amide coupling between carboxylic acids and amines. Using only 5 mol % of boronic acid catalyst and perfluoropinacol as an additive in a polar solvent mixture, the operationally simple protocol features mild conditions, a broad substrate scope, and a high functional group tolerance. A wide variety of diaryl, aryl-alkyl, heteroaryl-alkyl, and dialkyl oximes react under ambient conditions to afford high yields of amide products. Free alcohols, amides, carboxyesters, and many other functionalities are compatible with the reaction conditions. Investigations of the catalytic cycle revealed a novel boron-induced oxime transesterification providing an acyl oxime intermediate involved in a fully catalytic nonself-propagating Beckmann rearrangement mechanism. The acyl oxime intermediate was prepared independently and was subjected to the reaction conditions. It was found to be self-sufficient; it reacts rapidly, unimolecularly without the need for free oxime. A series of control experiments and 18O labeling studies support a true catalytic pathway involving an ionic transition structure with an active and essential role for the boronyl moiety in both steps of transesterification and rearrangement. According to 11B NMR spectroscopic studies, the additive perfluoropinacol provides a transient, electrophilic boronic ester that is thought to serve as an internal Lewis acid to activate the ortho-carboxyester and accelerate the initial, rate-limiting step of transesterification between the precatalyst and the oxime substrate.
