Ruthenium‐Catalyzed Reactions—A Treasure Trove of Atom‐Economic Transformations

Abstract

The demand for new chemicals spanning the fields of health care to materials science combined with the pressure to produce these substances in an environmentally benign fashion pose great challenges to the synthetic chemical community. The maximization of synthetic efficiency by the conversion of simple building blocks into complex targets remains a fundamental goal. In this context, ruthenium complexes catalyze a number of non-metathesis conversions and allow the rapid assembly of complex molecules with high selectivity and atom economy. These complexes often exhibit unusual reactivity. Careful consideration of the mechanistic underpinnings of the transformations can lead to the design of new reactions and the discovery of new reactivity.

Allene formation by gold catalyzed cross-coupling of masked carbenes and vinylidenes

“…LAu( 2 -alkyne) ϩ X Ϫ complexes such as 9a have been proposed as reactive intermediates in numerous catalytic cycles, but only a single isolable example has been reported (36). The yellow solution, resulting from subsequent addition of enamine 4a to a solution of 9a, was identified by 13 C and 1 H NMR spectroscopy as a 1:1 mixture of the neutral complex 10a (37) and salt 11a (Fig. 5); an independent preparation of 10a and 11a confirmed their identity.…”

“…Among them are reactions that directly couple two different sp 2 -hybridized carbon centers to form an olefin (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Conceptually, the simplest process would be the dimerization and cross-coupling of two free carbenes (Fig.…”

Homogeneous Chemoselective Hydrogenation of Heterocyclic Compounds – The Case of 1,4 Addition on Conjugated C-C and C-O Double Bonds of Arylidene Tetramic Acids

“…An appropriately structured Ru complex can catalyze very difficult and hard to achieve transformations. [13] The possibilities provided by the H4Ru4(CO)9[(S)-BINAP] complex employed here, have not yet been sufficiently investigated. Since the purpose of application is the hydrogenation of 3,5-bisarylidene tetramic acids the conditions of the reaction must be controlled absolutely in order to avoid side reactions.…”

“…Past reviews have indicated ruthenium as a transition metal with many possibilities depending on the environment provided. [13] Transformations including additions, redox isomerizations, coupling reactions and cycloadditions can be achieved using the appropriate ligands and reaction conditions. On the other hand, a large number of ligands has been developed and tested for their performance in asymmetric hydrogenation.…”

Ruthenium/TFA-catalyzed regioselective C-3-alkylation of indoles with terminal alkynes in water: efficient and unprecedented access to 3-(1-methylalkyl)-1H-indoles

“…9,10 In the context of these studies, a surprising and unprecedented result was encountered by performing the catalytic reactions in aqueous medium, 11 and in the presence of trifluoroacetic acid (TFA). Thus, as shown in Table 1, treatment of indole with excess of 1-hexyne (2.5 equiv.)…”