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1.6.1 Palladium-Mediated Domino Reactions

DOI: 10.1055/sos-SD-219-00234

Anderson, E. A.Science of Synthesis: Applications of Domino Transformations in Organic Synthesis, (20151449.

General Introduction

Among many metals that have been employed in domino transformations, palladium arguably holds a privileged position. The breadth of palladium-catalyzed transformations available to the organic chemist (and the accompanying depth of mechanistic understanding), combined with the wide tolerance by such reactions of many useful functionalities (carbonyls, heteroatoms, etc.), facilitates the design of sequenced orthogonal reaction processes, and has led to the development of a wide range of domino transformations that incorporate palladium catalysis. A necessary consideration for the design of any domino transformation[‌1‌‌4‌] is the relative rates of the processes involved in the reaction sequence, and the compatibility of each reaction step with a common set of conditions (reagents, solvents, temperature, etc.). As mentioned, orthogonality between each segment of the cascade is a useful (but not essential) factor, and palladium-catalyzed transformations are well suited for combination with other reaction manifolds.

In this section, the utility of palladium as a cascade-initiating component is discussed with a focus on applications in synthesis that exemplify reaction generality and wide substrate scope. The section is categorized according to the nature of the organopalladium intermediate initially generated in the cascade sequence, namely alkenylpalladium, arylpalladium, allylpalladium, allenylpalladium, and alkylpalladium complexes, with a degree of subcategorization according to the nature of subsequent transformations. As with any coverage of such a broadly useful topic, decisions were required as to the inclusion or omission of transformations. The chapter therefore aims to provide an informative and representative selection of reaction types as applied in a total or partial synthesis setting,[‌5‌] rather than a comprehensive coverage of the field, for which the reader is referred to more detailed reviews.[‌6‌‌9‌]