Transition Metals Participate In The Activation Of C(sp~3)-H To Form ?-bromocyclohexenone

Despite the tremendous advance in homogeneous gold catalysis in the past decade or so,the functionalization of unactivated C?sp³?-H bonds,a highly desirable and yet challenging streamlining synthetic strategy,has so far rarely been realized in this‘gold rush'.My graduate work was focused on the development of new strategies of gold catalysis to access highly reactive gold intermediates and harness their reactivities in insertion into unactivated C?sp³?-H bonds.An approach is discussed in this dissertation:via gold vinylidenes,fully functionalized gold vinylidenes generated from simple TMS-terminated alkynones facilely insert into unactivated alkyl groups to furnish versatile 2-bromocyclohexenones.First of all,we synthesized several gold catalysts and bromine oxidants and optimized the reaction conditions of C-H insertion reacation.We observed that IPr ^MeAu Cl and Ts NBr₂are the best gold catalyst and oxiant for the C-H insertion reacation respectively.Secondly,we designed and prepared some TMS-terminated alkynones and studied the scope of gold vinylidene C?sp³?-H insertion reactions.Interestingly,cycloalkyl substituted alkynones has higher reaction activity than chain alkyl substituted alkynones and fused bicyclic cyclohexenones were obtained by the vinylidene insertions into carbocycles of different sizes with highly regioselectivity and stereoselectivity.Thirdly,we studied the reaction mechanism and gave a proposed mechanism for gold vinylidene formation and C?sp³?-H insertion reaction.Cyclohexenones are exceptionally useful in organic synthesis,and the products via our streamlining C-H insertion strategy are more synthetically valuable because they possess extra?-bromination,which could be additionally functionalized,and also the starting materials can be easily synthesized from cheap and readily available ketone and carboxylic acid derivatives and most important,owing to the modulation by gold,The gold catalysis we developed here enable C?sp³?-H insertion by gold vinylidenes with good chemo-and diastereoselectivities.