ABSTRACT
An efficient method for the synthesis of isoquinolinone derivatives via photopromoted carboamination of alkynes is developed. Starting from the readily available propargyl alcohol derivatives, the polycyclic isoquinolinone derivatives could be obtained with good aryl and heterocycle tolerance. Both terminal and alkyl substituted alkynes could be employed. This protocol is operationally easy, and easily conducted on a gram-scale. A possible mechanism involving radical addition and cyclization following aromatization was proposed.
ABSTRACT
A cobalt-catalyzed asymmetric sequential hydroboration/isomerization/hydroboration of 2-aryl vinylcyclopropanes was for the first time reported for the preparation of valuable chiral 1,5-bis(boronates) in good yields with excellent enantioselectivity via asymmetric sequential isomerization/hydroboration of a trisubstituted alkene intermediate. The reaction was carried out smoothly and this protocol was used for asymmetric syntheses of (-)-preclamol in gram-scale. The two primary C(sp3) -B bonds in chiral 1,5-bis(boronates) could be distinguished in iterative Suzuki-Miyaura cross-coupling reaction, delivering chiral 1,2,5-triaryl alkanes with excellent enantioselectivity. Based on experimental and computational studies, a cobalt-hydride species was proposed as the active intermediate in hydroboration, isomerization, and second hydroboration reactions.
Subject(s)
Alkenes , Cobalt , Alkenes/chemistry , Catalysis , Cobalt/chemistry , Isomerism , StereoisomerismABSTRACT
Here, we reported for the first time an iron-catalyzed highly enantioselective hydrogenation of minimally functionalized 1,1-disubstituted alkenes to access chiral alkanes with full conversion and excellent ee. A novel chiral 8-oxazoline iminoquinoline ligand and its iron complex have been designed and synthesized. This protocol is operationally simple by using 1 atm of hydrogen gas and shows good functional group tolerance. A primary mechanism has been proposed by the deuterium-labeling experiments.
