BF3·Etherate-Mediated Friedel–Crafts Arylation of 2-Hydroxy-1,4-benzoxazines: Synthesis of 2-Aryl-1,4-benzoxazine Derivatives

Selective Construction of Diverse Polycyclic Spirooxindoles via a Three-Component Reaction of Cyclic Mercapto-Substituted β-Enamino Esters, Isatins, and Cyclic 1,3-Diketones

The three-component reaction of alkyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetates, isatins, and 1,3-indanedione (1,3-cyclopentanedione) in ethanol in the presence of acetic acid conveniently afforded spiro[indeno[1,2-b]phenothiazine-6,3'-indolines] or spiro[cyclopenta[b]phenothiazine-4,3'-indolines] in good yields and with high diastereoselectivity. More interestingly, a similar three-component reaction with 4-hydroxychromen-2-one resulted in the unexpected polycyclic spiro[benzo[b]chromeno[3',4':5,6]pyrano[2,3-e][1,4]thiazine-7,3'-indolines] in satisfactory yields. A plausible reaction mechanism was rationally proposed for formation of different kinds of the spiro compounds, and the stereochemistries of the various spiro compounds were clearly elucidated.

Controllable synthesis of 2- and 3-aryl-benzomorpholines from 2-aminophenols and 4-vinylphenols

We present herein a method for the controllable synthesis of 3-aryl-benzomorpholine and 2-aryl-benzomorpholine cycloadducts via cross-coupling/annulation between electron-rich 2-aminophenols and 4-vinylphenols. Molecular oxygen was successfully used in the reaction as the terminal oxidant and the complete inversion of chemoselectivity was achieved by the adjustment of the solvents and bases at room temperature.

Novel Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity as Both Solvents and Catalysts for Friedel–Crafts Alkylation

Unique tunable aryl-imidazolium magnetic ionic liquids with dual functions as a solvent–catalyst and dual Brønsted–Lewis acidity (B-L MILs) are applied for Friedel–Crafts alkylation without additional solvents. The catalytic properties of these B-L MILs in the Friedel–Crafts alkylation of p-xylene with benzyl chloride are investigated. The various reaction parameters, including the catalyst dosage, reaction time, reaction temperature, molar ratio of reactants, and reusability, are discussed. The results show that the B-L MIL 5c has more excellent product selectivity (>99%) and reactant conversion (>99%) under the following optimum conditions (reaction temperature = 80 °C, reaction time = 0.5 h, molar ratio of p-xylene to benzyl chloride = 6:1, and catalyst 5c dosage = 1.0 mole %) than traditional catalysts reported in the previous literature. Specifically, due to the mesomeric effect between the FeCl4 anion and hydrogen atom at cationic moiety, the catalyst B-L MILs with the molar fraction of FeCl3 equal to 0.5 can be easily recovered and provide satisfactory catalytic activity after being re-used six times.

Friedelane triterpenoids: transformations toward A-ring modifications including 2-homoderivatives

Common reaction strategies were employed on suitable substrates to achieve a series of C2,C3-; C3,C4- and C2,C3,C4-functionalized (including 2-homo-) friedelane triterpenoids with just one to four efficient steps.

FeCl3-Mediated Domino Reaction of Benzoxazinones with Aroylmethylidene Malonates: Synthesis to Functionalized Pyrrolobenzoxazines

An efficient domino approach for the synthesis of pyrrolobenzoxazine derivatives is described. The FeCl₃-promoted domino reaction between aroylmethylidene malonates and benzoxazinones has been successfully established to afford the title compounds in good to excellent yield under mild reaction conditions. The domino protocol provides a concise and straightforward access to highly substituted pyrrolobenzoxazines with high efficiency and excellent functional group tolerance.

BF3·OEt2 Mediated Regioselective Reaction of Electron-Rich Arenes with 3-Ylidene Oxindoles

A BF₃·OEt₂ mediated novel and regioselective protocol for the construction of a C-C bond between 3-ylidene oxindoles and electron-rich arenes has been successfully accomplished. The reaction was compatible with a wide variety of electron-rich arenes. A cascade reaction of 3-ylidene oxindoles with phenols and β-naphthol resulted in 2,3-difunctionalized benzofuran and lactone bearing indoline-2-one scaffolds under same conditions.

Selective construction of polycyclic spirooxindoles via a Cu(OTf)2/HOTf-catalyzed domino reaction of o-arylalkynylacetophenones and 3-phenacylideneoxindoles

Under the combined catalysis of Cu(OTf)₂/HOTf, the domino annulation reaction ofo-arylalkynyl acetophenones with 3-phenacylideneoxindoles in refluxing acetonitrile selectively afforded functionalized spiro[indoline-3,7′-tetrapheno[7,6-bc]furans].

Trifluoroacetic acid-promoted Michael addition-cyclization reactions of vinylogous carbamates

A simple and efficient methodology has been developed for the synthesis of pyrrolobenzoxazine and 3-arylamino coumarin derivatives promoted by trifluoroacetic acid. The initial step in the current protocol involves a Michael addition of the 1,4-benzoxazinone derivatives, a novel class of vinylogous carbamates to the Michael acceptors and subsequent cyclization.

TfOH-catalyzed synthesis of 3-aryl isoindolinones via a tandem reaction

A convenient method for the synthesis of 3-aryl isoindolinones via TfOH catalyzed C–H functionalization of arenes with 2-formylbenzonitriles is developed.