Chemo‑, Regio‑, and Enantioselective Rhodium-Catalyzed Allylation of Triazoles with Internal Alkynes and Terminal Allenes

The rhodium-catalyzed asymmetric <i>N</i>¹-selective and regioselective coupling of triazole derivatives with internal alkynes and terminal allenes gives access to secondary and tertiary allylic triazoles in very good enantioselectivities. For this process, three new members of the JosPOphos ligand family have been prepared and employed in catalysis. The optimized reaction conditions enable the coupling of triazoles with internal alkynes as well as with allenes, displaying a high tolerance for functional groups. A gram scale reaction provided <i>N</i>¹-allyltriazole, which was subjected to various transformations highlighting synthetic utility

Selective Hydrogenation of Carboxylic Acids to Alcohols or Alkanes Employing a Heterogeneous Catalyst

The chemoselective hydrogenation of carboxylic acids to either alcohols or alkanes is reported, employing a heterogeneous bimetallic catalyst consisting of rhenium and palladium supported on graphite. α-Chiral carboxylic acids were hydrogenated without loss of optical purity. The catalyst displays a reverse order of reactivity upon hydrogenation of different carboxylic functions with esters being less reactive than amides and carboxylic acids. This allows for chemoselective hydrogenation of an acid in the presence of an ester or an amide function

Rhodium-Catalyzed Regio- and Enantioselective Addition of <i>N</i>‑Hydroxyphthalimide to Allenes: A Strategy To Synthesize Chiral Allylic Alcohols

We achieved the first Rh-catalyzed regio- and enantioselective additions of <i>N</i>-hydroxyphthalimide to allenes. This transformation is accomplished via mild reaction conditions, leveraging on Josiphos SL-J003-2 as a chiral ligand to furnish branched <i>O</i>-allyl compounds in good yields with moderate to excellent enantioselectivities. The substrate scope is broad, and various functional groups are tolerated. The utility of this methodology is elaborated by transformation to allylic alcohols with different functional groups as well as to chiral <i>O</i>-allyl hydroxylamines

Rhodium-Catalyzed Chemo- and Regioselective Decarboxylative Addition of β‑Ketoacids to Allenes: Efficient Construction of Tertiary and Quaternary Carbon Centers

A rhodium-catalyzed chemo- and regioselective intermolecular decarboxylative addition of β-ketoacids to terminal allenes is reported. Using a Rh­(I)/DPPF system, tertiary and quaternary carbon centers were formed with exclusively branched selectivity under mild conditions. Preliminary mechanism studies support that the carbon–carbon bond formation precedes the decarboxylation and the reaction occurs in an outer-sphere mechanism

Palladium-Catalyzed Direct C–H Allylation of Electron-Deficient Polyfluoroarenes with Alkynes

A palladium-catalyzed intermolecular direct C–H allylation of polyfluoroarenes with alkynes is reported. Unlike classic hydroarylation reactions, alkynes are used as allylic electrophile surrogates in this direct aromatic C–H allylation. As an atom-economic and efficient method, various linear allylated fluoroarenes were synthesized from two simple and easy-to-access feedstocks in good to excellent yields, as well as regio- and stereoselectivity

Palladium-Catalyzed Stereoselective Cyclization of <i>in Situ</i> Formed Allenyl Hemiacetals: Synthesis of Rosuvastatin and Pitavastatin

A diastereoselective palladium-catalyzed cyclization of allenyl hemiacetals is described. It permits the selective synthesis of 1,3-dioxane derivatives, precursors for <i>syn</i>-configured 1,3-diols which make an appearance in all of the statin representatives. The reaction allows the total synthesis of Rosuvastatin and Pitavastatin in a straightforward fashion

Rhodium-Catalyzed Enantioselective Decarboxylative Alkynylation of Allenes with Arylpropiolic Acids

A rhodium-catalyzed chemo-, regio-, and enantioselective intermolecular decarboxylative alkynylation of terminal allenes with arylpropiolic acids is reported. Employing a Rh­(I)/(<i>R</i>)-Tol-BINAP catalytic system, branched allylic 1,4-enynes were obtained under mild conditions. The overall utility of this protocol is exemplified by a broad functional group compatibility

Enantioselective Redox-Neutral Rh-Catalyzed Coupling of Terminal Alkynes with Carboxylic Acids Toward Branched Allylic Esters

We report on the first enantioselective variant of the atom-economic and redox-neutral coupling of carboxylic acids with terminal alkynes under rhodium catalysis utilizing the chiral, bidentate (<i>R</i>,<i>R</i>)-Cp-DIOP ligand. This represents the first example of this convenient asymmetric access to valuable branched allylic esters. The utility of this methodology is demonstrated by both a reaction performed on large scale and a short three-step synthesis of two naturally occurring γ-butyrolactones. A stereochemical model explaining the observed absolute configuration of the products based on DFT calculations is given

Enantioselective Synthesis of Branched Allylic Esters via Rhodium-Catalyzed Coupling of Allenes with Carboxylic Acids

We report on the first intermolecular asymmetric catalytic regio- and enantioselective addition of carboxylic acids to terminal allenes to form valuable branched allylic esters, employing a rhodium­(I)/(<i>R,R</i>)-DIOP catalyst system

Direct Transformation of Terminal Alkynes to Branched Allylic Sulfones

A new strategy for the transformation of terminal alkynes to branched allylic sulfones was developed. Using a Rh­(I)/DPEphos/benzoic acid catalyst system, terminal alkynes react with sulfonyl hydrazides to produce branched allylic sulfones with good to excellent yields and selectivities in general