The stereomutations in a class of tris(pentafluorophenyl)borane-benzotriazole adducts are investigated by means of variable-temperature F-19 NMR and X-ray crystallography. At low temperature the presence of a pair of conformational enantiomers is confirmed by NMR spectra obtained in a chiral medium. Two different energy barriers, corresponding to an enantiomerization process and a B-N rotation, were observed and their values measured (Delta G double dagger = 10.7 and 12.8 kcal mol(-1) in the case of 1). In the case of the bis-adduct 3, two conformational diastereoisomers with different populations were detected at low temperature, while only one diastereoisomer is present in the crystalline state.
Conformational behavior of tris(pentafluorophenyl)borane-benzotriazole adducts / F. Focante, R. Leardini, A. Mazzanti, P. Mercandelli, D. Nanni. - In: ORGANOMETALLICS. - ISSN 0276-7333. - 25:9(2006), pp. 2166-2172.
Conformational behavior of tris(pentafluorophenyl)borane-benzotriazole adducts
P. MercandelliPenultimo
;
2006
Abstract
The stereomutations in a class of tris(pentafluorophenyl)borane-benzotriazole adducts are investigated by means of variable-temperature F-19 NMR and X-ray crystallography. At low temperature the presence of a pair of conformational enantiomers is confirmed by NMR spectra obtained in a chiral medium. Two different energy barriers, corresponding to an enantiomerization process and a B-N rotation, were observed and their values measured (Delta G double dagger = 10.7 and 12.8 kcal mol(-1) in the case of 1). In the case of the bis-adduct 3, two conformational diastereoisomers with different populations were detected at low temperature, while only one diastereoisomer is present in the crystalline state.
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