Enantioselective construction of a tetrasubstituted stereocenter in isoindolinones via an organocatalyzed reaction between ketones and 3-hydroxyisoindolinones

In(III)-Catalyzed 1,2-Hydrophosphorylation of 3-Alkynyl-3-hydroxyisoindolinones to 3,3-Disubstituted Isoindolinones Featuring Both Phosphoryl and Alkynyl Groups at the C3-Position

We report a highly regioselective 1,2-addition of P(O)-H compounds to the in situ generated β,γ-alkynyl-α-ketimine derived from 3-alkynyl-3-hydroxyisoindolinones, which provided a general protocol for the preparation of 3,3-disubstituted isoindolinones featuring both phosphoryl and alkynyl groups at a quaternary carbon center. The use of only 2-5 mol % of an inexpensive catalyst (In(ClO4)3·8H2O or Bi(OTf)3) allowed the smooth output of the desired products under mild conditions (25 °C, 0.5-24 h) with a broad substrate scope (35 examples) in up to >99% yield. The obtained products could be further elaborated based on the alkyne moiety. The initial asymmetric trial indicated that the use of BINOL-derived CPA could enable an enantioselective induction in up to a 46% yield with 77% ee.

Synthesis of 3-propargyl isoindolinones by Pd/Cu-catalyzed enantioselective Heck/Sonogashira reaction of enamides

Herein, we report an enantioselective Pd/Cu-catalyzed sequential Heck/Sonogashira coupling reaction of electron-rich enamides with terminal alkynes as substrates. This transformation proceeds smoothly to afford 3-propargyl isoindolinone derivatives bearing quaternary stereogenic centers in moderate to good yields (43-77% yield) and good to excellent enantioselectivity (up to 93% ee). Functional groups such as halogen atoms (F, Cl, and Br), thienyl, and silyl moieties are tolerated well. Synthetic transformations of the 3-propargyl isoindolinone product show the utility value of the reaction.

Cu(II) Coordination Polymers for the Selective Oxidation of Biomass-Derived Veratryl Alcohol in Green Solvents: A Sustainable Catalytic Approach

Four air-stable one-dimensional copper(II) coordination polymers (CP1-CP4) with azide linkers were synthesized using tridentate NNS and NNN ligands. Single-crystal X-ray diffraction (XRD) analysis confirmed the molecular structures of CP1, CP3, and CP4. In the presence of TEMPO, all four coordination polymers demonstrated effective catalytic activity for the selective aerobic oxidation of veratryl alcohol, a biomass model compound, under base-free conditions. CP4 exhibited the best catalytic efficiency. Oxidations were conducted at ambient temperature (40 °C) utilizing air as a sustainable oxidant. Selective oxidation of veratryl alcohol to veratraldehyde was also conducted in the presence of a catalytic amount of base (5 mol %), and enhanced reactivity was observed. The green solvents, acetone, and water, were used to maximize sustainability. The optimized reaction conditions were applied to broaden the substrate scope of various lignin model alcohols and substituted benzylic alcohols with wide electronic variability. CP4 exhibited high recyclability, consistently providing quantitative yields even after ten consecutive runs. The catalytic protocol demonstrated sustainability and environmental compatibility, as evidenced by a low E-factor (4.29) and a high Eco-scale score (90). Based on experimental evidence and theoretical calculations, a plausible catalytic cycle was proposed. Finally, the sustainability credentials of the different optimized reaction protocols were evaluated using the CHEM21 green metrics toolkit.

Copper-catalyzed asymmetric 1,2-arylboration of enamines: access to chiral borate-containing 3,3'-disubstituted isoindolinones

An enantioselective copper-catalyzed 1,2-arylboration reaction of enamines has been developed by employing (R)-xyl-BINAP as a chiral ligand. A number of chiral borate-containing 3,3'-disubstituted isoindolinones were obtained in moderate to good yields and good to excellent enantioselectivities from the reactions of N-(o-iodobenzoyl)enamines and bis(pinacolato)diboron (B2pin2) under mild reaction conditions. Synthetic transformations of the products were conducted to demonstrate the practicality of this reaction.

Dehydrative alkynylation of 3-hydroxyisoindolinones with terminal alkynes for the synthesis of 3-alkynylated 3,3-disubstituted isoindolinones

A brand-new procedure for the synthesis of 3-alkynylated 3,3-disubstituted isoindolinones has been disclosed via a HOTf or Fe(OTf)3-catalyzed dehydrative alkynylation of 3-hydroxyisoindolinones with terminal alkynes. Aryl, alkenyl and alkyl terminal alkynes are suitable to couple with a broad range of 3-hydroxyisoindolinones to afford the desired products in moderate to good yields. This protocol features the use of an inexpensive catalyst, mild reaction conditions, broad substrate scope and easy elaboration of the products.

Thermodynamic Controlled Regioselective C1-Functionalization of Indolizines with 3-Hydroxyisoindolinones via Brønsted Acid Catalyzed aza-Friedel-Crafts Reaction

A Brønsted acid catalyzed aza-Friedel-Crafts reaction of indolizines with 3-hydroxyisoindolinones has been established, which constructs isoindolinone derivatives bearing a tetrasubstituted stereocenter in good to high yields and enantioselectivities. Notably, this strategy provides a new access to C1-functionalization of indolizines with excellent regioselectivities. Moreover, this intriguing C1-regioselective transformation was induced under thermodynamic control.

Catalytic asymmetric addition to cyclic N-acyl-iminium: access to sulfone-bearing contiguous quaternary stereocenters

Herein, we report the first chiral phosphoric acid (CPA)-catalyzed asymmetric addition of α-fluoro(phenylsulfonyl)methane (FSM) derivatives to in situ generated cyclic N-acyliminium. This process enables metal-free expeditious access to sulfone and fluorine incorporating contiguous all substituted quaternary stereocenters ingrained in biorelevant isoindolinones in excellent stereoselectivities (up to 99% ee and up to 50 : 1 dr).

Enantioselective Construction of Tetrasubstituted Carbon Stereocenters via Chiral Phosphoric Acid-Catalyzed Friedel-Craft Alkylation of Indoles with 5-Substituted Hydroxybutyrolactams

The first intermolecular organocatalytic enantioselective addition of indoles to prochiral 5-membered cyclic N-acyliminium ions, generated from 5-hydroxy-α,β-unsaturated pyrrolidin-2-ones, is reported hereinafter. The reaction proceeds smoothly with a range of 5-hydroxy-5-substituted-α,β-unsaturated pyrrolidin-2-ones and indoles using BINOL-derived phosphoric acid catalyst to afford α,β-unsaturated lactams embedding a tetrasubstituted stereogenic center in high yields and enantioselectivities.

Enantioselective intramolecular Pictet–Spengler type annulation of indole-linked 3-methyleneisoindolin-1-ones

Asymmetric intramolecular Pictet–Spengler type annulation of indole-linked 3-methyleneisoindolin-1-ones provided isoindolinone fused tetrahydro β-carbolines with moderate to good enantioselectivities.

An overview of the applications of chiral phosphoric acid organocatalysts in enantioselective additions to CO and CN bonds

Since 2004, chiral phosphoric acids (CPAs) have emerged as highyl efficient organocatalysts, providing excellent results in a wide reaction scope. In this review, the applications of CPA for enantioselective additions to CO and CN bonds are covered.