Sigmatropic rearrangements of ynamides in stereoselective synthesis of complex molecular architectures: a comprehensive review.

Transition metal- and Lewis acid-catalysed stereoselective sigmatropic rearrangements of organic molecular scaffolds bearing ynamides or their derivatives have achieved substantial progress during the last two decades, showing contemporary interest in the exploration of ynamide chemistry. The reactivity and chemical characteristics of ynamides are mostly determined by the triple bond's intrinsic interaction with the adjacent electron-donating nitrogen atom. The typical polarity of C-N functionality coincides with a diverse array of synthetic possibilities that go well beyond conventional alkyne chemistry. Due to their electronic polarity, ynamides generate a keteniminium intermediate in situ in various catalytic systems, which can be employed in reactions that require high levels of regio- and stereoselectivity toward the development of strategies for the synthesis of structurally versatile N-containing complex molecular frameworks. These strategies reflect the constant striving and creativity in the design and execution of new synthetic methods utilizing ynamides. The present review summarises the current state of the art for the design of stereoselective sigmatropic rearrangements of ynamides and their derivatives, leading to the formation of natural product precursors and molecules bearing quaternary or tertiary stereocentres in both cyclic and acyclic frameworks. The organization of this review relies on the synthetic strategies developed to date and is divided into sections depending on the type of sigmatropic rearrangements. Due to the ready availability of a wide range of ynamides obtained from straightforward synthetic methods and commercial sources, it can be predicted that this field of chemistry will continue to grow in the coming years, providing an excellent opportunity for further enrichment of mainstream synthetic strategies.