Cu(I)-catalyzed α-alkylation of ketones with styrene derivatives

Synthesis of Allenes by Hydroalkylation of 1,3-Enynes with Ketones Enabled by Cooperative Catalysis

A method for the synthesis of allenes by the addition of ketones to 1,3-enynes by cooperative Pd(0)Senphos/B(C6F5)3/NR3 catalysis is described. A wide range of aryl- and aliphatic ketones undergo addition to various 1,3-enynes in high yields at room temperature. Mechanistic investigations revealed a rate-determining outer-sphere proton transfer mechanism, which was corroborated by DFT calculations.

α-Alkylation of Ketones with Alkenes Enabled by Photoinduced Activation of Silyl Enol Ethers in the Presence of a Small Amount of Water

Under blue-light irradiation conditions with a photocatalyst [1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene], silyl enol ethers reacted with alkenes in the presence of a small amount of water to afford the α-alkylation products in good to high yields. A thiol cocatalyst was found to expand the substrate scope of the reaction.

Catalytic alkylation reactions of weakly acidic carbonyl and related compounds using alkenes as electrophiles

Catalytic alkylation reactions of weakly acidic carbonyl and related pronucleophiles such as amides, esters, and sulfonamides with substituted alkenes have been reported.

Transition metal-catalyzed ketone-directed or mediated C-H functionalization

Transition metal-catalyzed C-H functionalization has evolved into a prominent and indispensable tool in organic synthesis. While nitrogen, phosphorus and sulfur-based functional groups (FGs) are widely employed as effective directing groups (DGs) to control the site-selectivity of C-H activation, the use of common FGs (e.g. ketone, alcohol and amine) as DGs has been continuously pursued. Ketones are an especially attractive choice of DGs and substrates due to their prevalence in various molecules and versatile reactivity as synthetic intermediates. Over the last two decades, transition metal-catalyzed C-H functionalization that is directed or mediated by ketones has experienced vigorous growth. This review summarizes these advancements into three major categories: use of ketone carbonyls as DGs, direct β-functionalization, and α-alkylation/alkenylation with unactivated olefins and alkynes. Each of these subsections is discussed from the perspective of strategic design and reaction discovery.

Copper-catalyzed trifluoromethylation of alkenes: synthesis of trifluoromethylated benzoxazines

A ligand and base free copper catalyzed method has been developed for the construction of trifluoromethylated benzoxazines by using Umemoto's reagent.

Palladium-catalyzed cross-coupling of styrenes with aryl methyl ketones in ionic liquids: direct access to cyclopropanes

The combined use of Pd(OAc)2 , Cu(OAc)2 , and dioxygen in molten tetrabutylammonium acetate (TBAA) promotes an unusual cyclopropanation reaction between aryl methyl ketones and styrenes. The process is a dehydrogenative cyclizing coupling that involves a twofold CH activation at the α-position of the ketone. The substrate scope highlights the flexibility of the catalyst; a reaction mechanism is also proposed.

Regioselective ketone α-alkylation with simple olefins via dual activation

Alkylation of carbonyl compounds is a commonly used carbon-carbon bond–forming reaction. However, the conventional enolate alkylation approach remains problematic due to lack of regioselectivity, risk of overalkylation, and the need for strongly basic conditions and expensive alkyl halide reagents. Here, we describe development of a ketone-alkylation strategy using simple olefins as the alkylating agents. This strategy employs a bifunctional catalyst comprising a secondary amine and a low-valent rhodium complex capable of activating ketones and olefins simultaneously. Both cyclic and acyclic ketones can be mono-α-alkylated with simple terminal olefins, such as ethylene, propylene, 1-hexene, and styrene, selectively at the less hindered site; a large number of functional groups are tolerated. The pH/redox neutral and byproduct-free nature of this dual-activation approach shows promise for large-scale syntheses.