Gold catalyzed novel transformations of Ynamide

Abstract : General introductionSince the pioneering work by Ito, Hayashi, Unimoto and Hashmi in late of last century, homogeneous gold catalysis has witnessed tremendous development by contributions from research groups all over the world. Gold catalysts, possessing unique catalytic reactivity, intrigued a large number of novel approaches to target molecules which cannot be accessed by other methodology. Ynamide, which belongs to a subclass of hetero-substituted alkynes, represents a versatile building block with balanced reactivity and stability and found a series of applications in useful transformations, such as additions, cycloadditions and cycloisomerizations.As part of our ongoing interest in gold catalysis and ynamide chemistry, in this manuscript, two works involving ynamide in the presence of gold catalyst was presented:1). Gold(I)-Catalyzed Rearrangement of Propargyl Ethers of ynamides: A Practical Method for the synthesis of Substituted AllenamidesAllenamides are versatile synthetic building blocks that have seen numerous applications and therefore great efforts have been devoted to the access to such compounds. We have shown that a series of substituted and functionalized allenamides were easily accessible via a gold catalysted 1,5-hydride shift/fragmentation sequence using ynamides as the starting material. Our method is rapid and practical. It can be performed under very mild conditions (room temperature) with low catalyst loading (4% gold catalyst) and gave excellent yields (up to 99% yield). Besides the good functionality compatibility in the carbon terminal (R1 and R2), our method also tolerate variuous Nitrogen substituents (R’ and R’’). Moreover, further transformation using in-situ formed allenamides was achieved. Some interesting spiral and diene compounds were also formed in excellent yield.2). Dual gold catalysis: a unique approach to derived-tetrahydroquinolines by a formal [4+2] pathwayAlthough vast majority of gold catalysis features π-activation of a multiple bond by a single gold complex, recent innovative advance involving two gold centers in one single molecule was disclosed recently by several research groups and also by our group.The catalytic cycle was initiated by the formation of gold acetylide and coordination of another gold complex to the triple bond of ynamide. After nucleophilic attack of gold acetylide onto ynamide, gold vinylidene was generated. The formed gold vinylidene was then trapped by double bond, giving rise to aromatic rings.
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Qing Zhao. Gold catalyzed novel transformations of Ynamide. Organic chemistry. Université Paris-Saclay, 2016. English. ⟨NNT : 2016SACLX060⟩. ⟨tel-01495607⟩

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