Asymmetric Synthesis of Hydrodibenzofurans from Norcaradienes: Kinetic Resolution via [3 + 2] Cycloaddition with Quinones

The catalytic asymmetric [3 + 2] cycloaddition of racemic norcaradienes with quinones to construct multicyclic hydrodibenzofurans was achieved by the use of chiral N,N′-dioxide/metal complex catalysts. Kinetic resolution of norcaradienes accompanied by partial racemization occurred, and one enantiomer in prior acted as the C2 synthon to participate in diastereoselective cycloaddition. An enantiodivergent synthesis via a switch of metal ions was observed when naphthoquinone was used as the partner. DFT calculations revealed the profiles of the cycloaddition processes

Organocatalytic Asymmetric Cascade Reaction of 2‑Hydroxyphenyl-Substituted Enones and Isocyanates To Construct 1,3-Benzoxazin-2-ones

The development of a new bisguanidinium salt as a multifunctional organocatalyst for asymmetric cascade esterification/aza-Michael reaction between 2-hydroxyphenyl-substituted enones and isocyanates is reported. A high level of enantioinduction and excellent isolated yields were achieved under mild reaction conditions. Enantiomerically enriched 1,3-benzoxazin-2-ones were constructed, and a possible catalytic model was suggested based on the mechanism-driven experiments

Asymmetric Organocatalytic Cyclopropanation of Cinnamone Derivatives with Stabilized Sulfonium Ylides

A simple chiral diamine catalyst <b>1h</b> was successfully applied in the asymmetric cyclopropanation of cinnamone derivatives with stabilized sulfur ylides. The desired cyclopropanation adducts were obtained in moderate yields (up to 68%) with good enantioselectivities (67–93% <i>ee</i>) and excellent diastereoselectivities (>95:5) under mild conditions

Construction of Distant Stereocenters by Enantioselective Desymmetrizing Carbonyl–Ene Reaction

An efficient desymmetrizing carbonyl–ene reaction of 1-substituted 4-methylenecyclohexanes with glyoxal derivatives was thus executed by a chiral <i>N</i>,<i>N</i>′-dioxide/Ni^II catalyst, providing facile access to cyclohexene derivatives bearing two remote 1,6-related stereocenters. This distal stereocontrol methodology originates from the efficient interaction between the catalyst with enophiles, discrimination of the two chair conformations of olefinic components, and the intrinsic six-membered transition-state structure of ene process

Fluorescent Sensor Based on BINOL for Recognition of Cysteine, Homocysteine, and Glutathione

A new and simple fluorescent sensor based on unmodified BINOL was developed. The fluorescence of BINOL could be turned off with high selectivity toward Cu­(II) among 27 metal ions. Meanwhile, it was found that BINOL was oxidized to dibenzo­[<i>a</i>,<i>kl</i>]­xanthen-1-ol (<b>A</b>) by Cu­(NO₃)₂. A new peak appeared at ∼482 nm upon addition of thiol-containing cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). Thus, a cascade recognition of Cu­(II) and Cys, Hcy, and GSH are well presented

Nickel(II)-Catalyzed Enantioselective α‑Vinylation of β‑Keto Amides/Esters with Hypervalent Iodine Salts

The enantioselective α-vinylation of β-keto amides/esters using hypervalent iodine salts has been accomplished via a chiral <i>N</i>,<i>N</i>′-dioxide–nickel­(II) complex promoted electrophilic addition and reductive elimination process. A wide range of vinyl-substituted all-carbon quaternary β-keto amides/esters were obtained in high yields and ee values (up to 99% yield and 99% ee). Moreover, the catalytic system has been applied to the enantioselective alkynylation/arylation of β-ketoamides with good results

Nickel(II)-Catalyzed Enantioselective α‑Vinylation of β‑Keto Amides/Esters with Hypervalent Iodine Salts

The enantioselective α-vinylation of β-keto amides/esters using hypervalent iodine salts has been accomplished via a chiral <i>N</i>,<i>N</i>′-dioxide–nickel­(II) complex promoted electrophilic addition and reductive elimination process. A wide range of vinyl-substituted all-carbon quaternary β-keto amides/esters were obtained in high yields and ee values (up to 99% yield and 99% ee). Moreover, the catalytic system has been applied to the enantioselective alkynylation/arylation of β-ketoamides with good results

Organocatalytic Asymmetric Cascade Reaction of 2‑Hydroxyphenyl-Substituted Enones and Isocyanates To Construct 1,3-Benzoxazin-2-ones

The development of a new bisguanidinium salt as a multifunctional organocatalyst for asymmetric cascade esterification/aza-Michael reaction between 2-hydroxyphenyl-substituted enones and isocyanates is reported. A high level of enantioinduction and excellent isolated yields were achieved under mild reaction conditions. Enantiomerically enriched 1,3-benzoxazin-2-ones were constructed, and a possible catalytic model was suggested based on the mechanism-driven experiments

Enantioselective Synthesis of 2,2,3-Trisubstituted Indolines via Bimetallic Relay Catalysis of α‑Diazoketones with Enones

An efficient asymmetric intramolecular trapping of ammonium ylides of α-diazoketones with enones to synthesize indoline derivatives was realized. A Rh­(II)/chiral <i>N,N′</i>-dioxide−Sc­(III) complex bimetallic relay catalytic system was established. A series of optically active 2,2,3-trisubstituted indolines were obtained in high yields (up to 99%), good enantioselectivities (up to 99% ee), and excellent diastereoselectivities (up to >19:1 dr) under mild reaction conditions

Chiral <i>N</i>,<i>N</i>′‑Dioxide Organocatalyzed Asymmetric Electrophilic α‑Cyanation of β‑Keto Esters and β‑Keto Amides

An enantioselective electrophilic α-cyanation of 1-indanone-derived β-keto esters and β-keto amides using a hypervalent iodine as the cyanide-transfer reagent was realized. A chiral <i>N</i>,<i>N</i>′-dioxide was used as the efficient bifunctional organocatalyst in the presence of inorganic base, which gave the corresponding α-cyano dicarbonyl compounds in yields of 50–99% with good enantioselectivities (87–97% ee)