title: Mechanisms and origins of the switchable regioselectivity of FeBr3-catalyzed [1,2]-aryl and [1,2]-alkyl shifts of α-aryl aldehydes.
abstract: With the aid of DFT calculations, the FeBr3-catalyzed skeletal rearrangements of 2-cyclohexanal,2-p-C6H4OMe-propylaldehyde (1A) and 2-phenyl,2-p-C6H4OMe-propylaldehyde (1B) were investigated theoretically. As compared to mono-FeBr3 as a catalyst, the bis-FeBr3 serving as a catalyst is found to be not only enhancing the catalytic efficiency but also improving the product selectivity. For the reaction starting from 1A, the [1,2]-group shift (first step) is rate-determining, and why the Cy shift is the most favored is rationalized in comparison with the p-C6H4OMe and Me shifts. For the reaction starting from 1B, the [1,2]-H shift (second step) is rate-determining although the [1,2]-p-C6H4OMe shift is favored over the [1,2]-phenyl shift. In contrast to the experimental proposal, the newly established H2O/Br(-) joint-assisted H-shift mechanism explains the partial α-H source of the [1,2]-Cy shift product. In addition, we discussed the inherent mechanism that explains why both the [1,2]-p-C6H4OMe and [1,2]-p-C6H4CF3 shifts are more facile than the [1,2]-phenyl shift although the substituents -OMe and -CF3 have opposite electronic behaviors.
authors.affiliation: College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China. liuyuxia2008@163.com siweibi@126.com.
authors.forename: Congcong
authors.initials: C
authors.lastname: Liu
authors.affiliation: College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China. liuyuxia2008@163.com siweibi@126.com.
authors.forename: Yuxia
authors.initials: Y
authors.lastname: Liu
authors.affiliation: College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China. liuyuxia2008@163.com siweibi@126.com.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Tang
authors.affiliation: College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China. liuyuxia2008@163.com siweibi@126.com.
authors.forename: Haosheng
authors.initials: H
authors.lastname: Liang
authors.affiliation: College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, P. R. China. liuyuxia2008@163.com siweibi@126.com.
authors.forename: Siwei
authors.initials: S
authors.lastname: Bi