Enantioselective Synthesis of α-Allyl-α-aryldihydrocoumarins and 3-Isochromanones via Pd-Catalyzed Decarboxylative Asymmetric Allylic Alkylation

Asymmetric Synthesis of Quaternary α-Aryl Stereocentres in Benzofuran-3(2H)-Ones Using Decarboxylative Asymmetric Allylic Alkylation

The Pd-catalysed decarboxylative asymmetric allylic alkylation (DAAA) has been applied to the enantioselective synthesis of sterically hindered benzofuran-3(2H)-one-derived α-aryl-β-keto esters employing the (R,R)-ANDEN phenyl Trost ligand. A range of substrates were synthesised, employing previously developed aryllead triacetate methodology to install various aryl groups. The resulting α-aryl-α-allyl benzofuran-3(2H)-one DAAA products were obtained in moderate to high yields and in enantioselectivities of up to 96 % ee, with the best results observed for substrates containing a di-ortho-substitution pattern on the aryl ring as well as naphthyl-containing substrates.

Pd-Catalysed asymmetric allylic alkylation of heterocycles: a user's guide

This review provides an in-depth analysis of recent advances and strategies employed in the Pd-catalysed asymmetric allylic alkylation (Pd-AAA) of nucleophilic prochiral heterocycles. The review is divided into sections each focused on a specific family of heterocycle, where optimisation data and reaction scope have been carefully analysed in order to bring forward specific reactivity and selectivity trends. The review eventually opens on how computer-based technologies could be used to predict an ideally matched catalytic system for any given substrate. This user-guide targets chemists from all horizons interested in running a Pd-AAA reaction for the preparation of highly enantioenriched heterocyclic compounds.

Transition Metal-Catalyzed Enantioselective Synthesis of Chiral Five- and Six-Membered Benzo O-heterocycles

Enantiomerically enriched five- and six-membered benzo oxygen heterocycles are privileged architectures in functional organic molecules. Over the last several years, many effective methods have been established to access these compounds. However, comprehensive documents cover updated methodologies still in highly demand. In this review, recent transition metal catalyzed transformations lead to chiral five- and six-membered benzo oxygen heterocycles are presented. The mechanism and chirality transfer or control processes are also discussed in details.

The catalytic decarboxylative allylation of enol carbonates: the synthesis of enantioenriched 3-allyl-3'-aryl 2-oxindoles and the core structure of azonazine

The catalytic asymmetric synthesis of 3-allyl-3'-aryl 2-oxindoles has been shown via the Pd(0)-catalyzed decarboxylative allylation of allylenol carbonates. This methodology provides access to a variety of 2-oxindole substrates (5a-v) with all-carbon quaternary stereocenters (up to 94% ee) at the pseudobenzylic position under additive-free and mild conditions. The synthetic potential of this method was shown by the asymmetric synthesis of the tetracyclic core of the diketopiparazine-based alkaloid azonazine (11).

Palladium-Catalyzed Regiospecific Decarboxylative Allylation of (Cyclohexadienylidene)malononitriles: Access to α-Allyl-α-aryl Malononitriles

A palladium-catalyzed regiospecific decarboxylative ε-allylation of (cyclohexadienylidene)malononitriles is presented for the synthesis of functionalized α-allyl-α-aryl malononitriles. This reaction proceeds via a resonance-stabilized α-aryl malononitrile anion, resulting in a wide range of α-allyl-α-aryl malononitriles in high yields with excellent linear product selectivity. We have also shown that the resulting products can be transformed into valuable synthetic intermediates by decyanation and Mizoroki-Heck arylation. In addition, an enantioselective decarboxylative allylation reaction is also presented.

Catalytic Enantioselective Alkylation of Prochiral Enolates

The asymmetric alkylation of enolates is a particularly versatile method for the construction of α-stereogenic carbonyl motifs, which are ubiquitous in synthetic chemistry. Over the past several decades, the focus has shifted to the development of new catalytic methods that depart from classical stoichiometric stereoinduction strategies (e.g., chiral auxiliaries, chiral alkali metal amide bases, chiral electrophiles, etc.). In this way, the enantioselective alkylation of prochiral enolates greatly improves the step- and redox-economy of this process, in addition to enhancing the scope and selectivity of these reactions. In this review, we summarize the origin and advancement of catalytic enantioselective enolate alkylation methods, with a directed emphasis on the union of prochiral nucleophiles with carbon-centered electrophiles for the construction of α-stereogenic carbonyl derivatives. Hence, the transformative developments for each distinct class of nucleophile (e.g., ketone enolates, ester enolates, amide enolates, etc.) are presented in a modular format to highlight the state-of-the-art methods and current limitations in each area.

Probing Trends in Enantioinduction via Substrate Design: Palladium-Catalyzed Decarboxylative Allylic Alkylation of α-Enaminones

Herein, we report the palladium-catalyzed decarboxylative asymmetric allylic alkylation of α-enaminones. In addition to serving as valuable synthetic building blocks, we exploit the α-enaminone scaffold and its derivatives as probes to highlight structural and electronic factors that govern enantioselectivity in this asymmetric alkylation reaction. Utilizing the (S)-t-BuPHOX ligand in a variety of nonpolar solvents, the alkylated products are obtained in up to 99% yield and 99% enantiomeric excess.

Synthesis of α-Aryl Oxindoles by Friedel-Crafts Alkylation of Arenes

α-Aryl oxindoles are accessed from isatin via a two-step procedure involving a phospha-Brook rearrangement and a Friedel-Crafts alkylation in a one-pot procedure. The use of 1,1,1,3,3,3-hexafluoro-2-propanol as solvent significantly extended the reaction substrate scope to include relatively less electron-rich arenes including benzene. This new alkylation method is fast and straightforward and allows for the direct introduction of the oxindole moiety onto a range of aromatic compounds including phenols. Additionally, the application of arylated products was shown in decarboxylative asymmetric allylation and protonation.

Cu-catalyzed enantioselective synthesis of tertiary benzylic copper complexes and their in situ addition to carbonyl compounds

Catalytic chemo- and enantioselective generation of tertiary benzylic copper complexes from Cu-B(pin) (pin = pinacolato) additions to 1,1-disubstituted alkenes followed by in situ reactions with ketones and carboxylic acid phenol esters to construct multifunctional alkylboron compounds that contain quaternary stereogenic centers is presented. The method is distinguished by the unprecedented reaction mode of tertiary benzylic Cu complexes, allowing reaction with a wide range of carbonyl electrophiles in good yields and with high chemo-, site-, diastereo- and enantioselectivity. The catalytic protocol was performed with easily accessible chiral ligands and copper salts at ambient temperature. Functionalization of multifunctional alkylboron products provides useful building blocks that are otherwise difficult to access.

Nickel-catalyzed enantioselective allylic alkylation of lactones and lactams with unactivated allylic alcohols

Reported is the first nickel-catalyzed enantioselective allylic alkylation of lactones and lactams to provide products bearing an all-carbon quaternary stereocenter.

The first nickel-catalyzed enantioselective allylic alkylation of lactone and lactam substrates to deliver products bearing an all-carbon quaternary stereocenter is reported. The reaction, which utilizes a commercially available chiral bisphosphine ligand, proceeds in good yield with a high level of enantioselectivity (up to 90% ee) on a range of unactivated allylic alcohols for both lactone and lactam nucleophiles. The utility of this method is further highlighted via a number of synthetically useful product transformations.

Iridium-Catalyzed Enantioselective Allylic Substitution of Aliphatic Esters with Silyl Ketene Acetals as the Ester Enolates

Enantioselective allylic substitution with enolates derived from aliphatic esters under mild conditions remains challenging. Herein we report iridium-catalyzed enantioselective allylation reactions of silyl ketene acetals, the silicon enolates of esters, to form products containing a quaternary carbon atom at the nucleophile moiety and a tertiary carbon atom at the electrophile moiety. Under relatively neutral conditions, the allylated aliphatic esters were obtained with excellent regioselectivity and enantioselectivity. These products were readily converted into primary alcohols, carboxylic acids, amides, isocyanates, and carbamates, as well as tetrahydrofuran and γ-butyrolactone derivatives, without erosion of enantiomeric purity.

Enantioselective synthesis of sterically hindered α-allyl–α-aryl oxindoles via palladium-catalysed decarboxylative asymmetric allylic alkylation

The highly enantioselective synthesis of sterically hindered α-allyl–α-aryl oxindoles possessing an all-carbon quaternary stereocenter at the oxindole 3-position has been developed.