1381772-75-3Relevant academic research and scientific papers
Mechanism and Dynamics of Intramolecular C-H Insertion Reactions of 1-Aza-2-azoniaallene Salts
Hong, Xin,Bercovici, Daniel A.,Yang, Zhongyue,Al-Bataineh, Nezar,Srinivasan, Ramya,Dhakal, Ram C.,Houk,Brewer, Matthias
supporting information, p. 9100 - 9107 (2015/08/03)
The 1-aza-2-azoniaallene salts, generated from α-chloroazo compounds by treatment with halophilic Lewis acids, undergo intramolecular C-H amination reactions to form pyrazolines in good to excellent yields. This intramolecular amination occurs readily at both benzylic and tertiary aliphatic positions and proceeds at an enantioenriched chiral center with retention of stereochemistry. Competition experiments show that insertion occurs more readily at an electron-rich benzylic position than it does at an electron-deficient one. The C-H amination reaction occurs only with certain tethers connecting the heteroallene cation and the pendant aryl groups. With a longer tether or when the reaction is intermolecular, electrophilic aromatic substitution occurs instead of C-H amination. The mechanism and origins of stereospecificity and chemoselectivity were explored with density functional theory (B3LYP and M06-2X). The 1-aza-2-azoniaallene cation undergoes C-H amination through a hydride transfer transition state to form the N-H bond, and the subsequent C-N bond formation occurs spontaneously to generate the heterocyclic product. This concerted two-stage mechanism was shown by IRC and quasi-classical molecular dynamics trajectory studies. (Chemical Equation Presented).
Stereospecific intramolecular C-H amination of 1-aza-2-azoniaallene salts
Bercovici, Daniel A.,Brewer, Matthias
, p. 9890 - 9893 (2012/08/08)
We report that 1-aza-2-azoniaallene salts, generated from α-chloroazo compounds by treatment with halophilic Lewis acids, participate in intramolecular C-H amination reactions to provide pyrazoline products in good to excellent yield. This intramolecular amination occurs readily at both benzylic and tertiary aliphatic positions and proceeds at an enantioenriched chiral center without loss of enantiomeric excess. A competition reaction shows that insertion occurs more readily at an electron-rich benzylic position than an electron-deficient one. These observations are consistent with the 1-aza-2-azoniaallene intermediate reacting as a nitrenium-like ion by a concerted insertion mechanism.
