More than Bystanders: The Effect of Olefins on Transition‐Metal‐Catalyzed Cross‐Coupling Reactions

Abstract

Olefins and alkynes are ubiquitous in transition-metal catalysis, whether introduced by the substrate, the catalyst, or as an additive. Whereas the impact of metals and ligands is relatively well understood, the effects of olefins in these reactions are generally underappreciated, even though numerous examples of olefins influencing the outcome of a reaction, through increased activity, stability, or selectivity, have been reported. This Review provides an overview of the interaction of olefins with transition metals and documents examples of olefins influencing the outcome of catalytic reactions, in particular cross-coupling reactions. It should thus provide a basis for the improved understanding and further utilization of olefin and alkyne effects in transition-metal-catalyzed reactions.

Collaborative Interaction of Carbon–Carbon Unsaturated Bond Groups with Transition-metal Catalysts for C–H Bond Functionalization

“…Arylisocyanates are applicable to this annulation with alkynoxyarenes under Pd(OAc) 2 , PCy 3 , and Zn(OAc) 2 catalytic conditions. For example, the reaction of a bisalkynoxybenzene with phenylisocyanate produced a benzo[1,2-b:4,5-b¤]bis [1,4]oxazine-3,8-dione (Scheme 31). 36 In this case, ortho-CH bonds are activated probably via a concerted metalation/ deprotonation (CMD) pathway.…”

Ligand‐Free Pd‐Catalyzed Carbonylative Cross‐Coupling Reactions under Atmospheric Pressure of Carbon Monoxide: Synthesis of Aryl Ketones and Heteroaromatic Ketones

“…It is well known that π-acid olefins can not only affect the rate of oxidative addition through formation of an active palladium species, but they might also play a role in stabilization of the catalyst. [8] Thus, we speculated that Pd 2 (dba) 3 as an olefin-containing catalyst would facilitate the catalytic reaction. The effect of temperature was not obvious and almost quantitative yield was obtained at either 80 or 100°C (Table 1, Entries 5 and 6).…”

“…For example, both 4-methylbenzeneboronic acid (2b) and 4-chlorophenylboronic acid (2c) reacted smoothly with aryl iodides to give unsymmetrical biaryl ketones in high yields ( Table 2, Entries 1-4). In addition, aryl iodides containing electron-withdrawing groups including CH 3 OCO, Br, and Cl produced desired ketones 3f, 3c, and 3h in good to excellent yields (Table 2, Entries 5,7,8). It is noteworthy that up to 85 % yield of 3g was obtained for 1d with the strong electron-withdrawing substituent NO 2 , known to promote the direct coupling reaction, to provide a mixture of biaryl and aryl ketone ( [5a,5d] The carbonylation of 4-bromoiodobenzene (1f) selectively occurred at the C-I bond, which gives an opportunity for further functionalization at the intact bromide group in the product ketone ( Table 2, Entry 8).…”

Rh-catalyzed asymmetric 1,4-addition reactions to α,β-unsaturated carbonyl and related compounds: an update

“…234 Based on the results of these 1,4-additions and the characterization of Rh/(S)-L62a complex by single crystal X-ray crystallography, a stereoselective route was suggested for the 1,4-addition of phenylboronic acid to 2-cyclohexenone under Rh/(S)-L62a catalysis as illustrated in Figure 12a. [235][236][237][238][239][240][241] As shown, the phenylrhodium species had a trans-relationship between the phenyl group and the olefin ligand, while 2-cyclohexenone binds to the rhodium with its si-face at the cis-position of the olefin ligand, resulting in the formation of the 1,4-adduct with an (S)-configuration. The generation of the (R)-product utilizing Rh/(S)-L62d can be explained similarly by the re-face coordination of 2-cyclohexenone to rhodium as depicted in Figure 12b (Tables 74-76).…”