Jingzhi Tian

New mechanisms centered on reactive intermediates : Examples from diazirine and carbene chemistry

Laser flash photolysis (LFP) of appropriate diazirine precursors afforded the UV spectra of methylchlorocarbene, benzylchlorocarbene, cyclopropylchlorocarbene, and 1-adamantylchlorocarbene. The σ → p transitions of these carbenes were used to directly monitor their reaction kinetics. The unusual and highly reactive N2CO compound, diazirinone, was obtained from the reaction of fluoride ion with p-nitrophenoxychlorodiazirine. Diazirinone fragmented to CO and N2 in a reaction that was exothermic by >90 kcal/mol. Dichlorodiazirine (DCD) was generated by the reaction of chloride ion with p-nitrophenoxychlorodiazirine. Reactions of dichlorocarbene generated from DCD are discussed.

Amplification of diastereoselectivity by cyclodextrins in the copper-mediated cleavages of methylphosphonamidothioates

Cu-mediated cleavage, coupled with diastereoselective binding and orientational preferences supplied by γ-cyclodextrin, lead to substantial kinetic diastereoselectivity between phosphonamidothioate diastereomers.