title: Origins of the enantio- and N/O selectivity in the primary-amine-catalyzed hydroxyamination of 1,3-dicarbonyl compounds with in-situ-formed nitrosocarbonyl compounds: a theoretical study.
abstract: Chemoselective control over N/O selectivity is an intriguing issue in nitroso chemistry. Recently, we reported an unprecedented asymmetric α-amination reaction of β-ketocarbonyl compounds that proceeded through the catalytic coupling of enamine carbonyl groups with in-situ-generated carbonyl nitroso moieties. This process was facilitated by a simple chiral primary and tertiary diamine that was derived from tert-leucine. This reaction featured high chemoselectivity and excellent enantioselectivity for a broad range of substrates. Herein, a computational study was performed to elucidate the origins of the enantioselectivity and N/O regioselectivity. We found that a bidentate hydrogen-bonding interaction between the tertiary N(+)-H and nitrosocarbonyl groups accounted for the high N selectivity, whilst the enantioselectivity was determined by Si-facial attack on the (E)- and (Z)-enamines in a Curtin-Hammett-type manner. The bidentate hydrogen-bonding interaction with the nitrosocarbonyl moieties reinforced the facial selectivity in this process.
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry the Chinese Academy of Sciences, Beijing, 100190 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300071 (China), Fax: 86-10-62554449.
authors.forename: Long
authors.initials: L
authors.lastname: Zhang
authors.forename: Changming
authors.initials: C
authors.lastname: Xu
authors.forename: Xueling
authors.initials: X
authors.lastname: Mi
authors.forename: Sanzhong
authors.initials: S
authors.lastname: Luo
keywords: computational chemistry; enamines; enantioselectivity; hydroxyamination; reaction mechanisms