In this paper, a metal-free protocol of nucleophilic ortho-halogenation and hydroxylation of anilines via an aromatic Pummerer process is reported.

We report an electrophilic cyclization of alkynyl imines to afford polysubstituted 3-haloquinolines using CuX-activated N-halosuccinimdes (NXS) as electrophiles. Control experiments demonstrated that the NXS/CuX system might be more active than single NXS and could be applied in the electrophilic cyclization of electron- deficient substrates.

A facile protocol for the synthesis of polysubstituted 1,2-dihydrocyclobuta[b]naphthalenes and 1,2-dihydrocyclobuta[b]anthracenes was developed via a sequence of base-promoted 1,5-H shift, intramolecular [2 + 2] cycloaddition, and aromatization. The synthesized 1,2-dihydrocyclobuta[b]anthracenes exhibited bright blue emissions in solution and strong yellow emissions in solid, which made them possible candidates for optoelectronic conjugated materials.

•A novel probe VC comprising coumarin as a fluorophore and a vinyl ether group as recognition unit is synthesized by optimizing the elimination reaction condition.•Probe VC treated with Hg2+ in HEPES buffer solution shows remarkable fluorescence enhancement.•Probe VC displays a high selectivity and sensitivity toward Hg2+ in neat aqueous solution, which is applied to detect Hg2+ in real water sample.A new probe VC comprising coumarin as a fluorophore and a vinyl ether group as recognition unit is designed and synthesized. The key synthetic step is investigated by elimination reaction using 7-bromoethaneoxy-4-methylcoumarin with different bases. The probe VC shows almost no fluorescence in HEPES buffer (20 mM, pH 7.0), while displays obvious fluorescence enhancement after addition of Hg2+. Recognition mechanism is studied by NMR titration and MS, suggesting that the strongly fluorescent appearance is attributed to 7-hydroxy-4-methylcoumarin, the Hg2+-promoted hydrolysis reaction product. Due to the irreversible reaction and coumarin fluorescence property, the probe VC exhibits remarkable selectivity and sensitivity toward Hg2+ (the detection limit is 0.12 μM). In addition, the detection experiment in real water sample reveals that probe VC could be used as a convenient tool to monitor Hg2+ in neat aqueous solution by fluorescence turn-on response.

β-Sulfonium carbanions, members of the organosulfur family, are ephemeral intermediates and difficult to apply in organic syntheses. We developed a new strategy toward relatively stable β-sulfonium carbanions, achieved by an intramolecular addition of the sulfur atom of a sulfide to the in situ generated electron-deficient allene moiety. These types of applicable β-sulfonium carbanions may indicate an unexplored area in which a bundle of synthetically useful building blocks are yet to be discovered.

The regioselective dibromohydration of N-(2-alkynylaryl)acetamide with the participation of a neighbouring acetamino group is described here for the synthesis of N-(2-(2,2-dibromo-2-arylacetyl)aryl)acetamide. The dibromohydration proceeds under mild conditions and works well without metal catalysis. More importantly, by employing different neighbouring groups, switchable synthesis can be achieved. The entire process of the dibromohydration of N-(2-alkynylaryl)acetamide consists of KBr/K2S2O8-based electrophilic 6-exo cyclization to form bromo-containing benzoxazine cation and the oxidative ring-opening of the resulting bromo-containing benzoxazine cation. Water serves as a reagent to be incorporated into the acetamino group.

The regioselective dibromohydration of N-(2-alkynylaryl)acetamide with the participation of a neighbouring acetamino group is described here for the synthesis of N-(2-(2,2-dibromo-2-arylacetyl)aryl)acetamide. The dibromohydration proceeds under mild conditions and works well without metal catalysis. More importantly, by employing different neighbouring groups, switchable synthesis can be achieved. The entire process of the dibromohydration of N-(2-alkynylaryl)acetamide consists of KBr/K2S2O8-based electrophilic 6-exo cyclization to form bromo-containing benzoxazine cation and the oxidative ring-opening of the resulting bromo-containing benzoxazine cation. Water serves as a reagent to be incorporated into the acetamino group.

•We report a new quinoline-based colorimetric chemosensor CQ for Cu2+ with high selectivity and sensitivity.•Test strips immersed sensor CQ can be used to conveniently monitor Cu2+ by naked-eyes.•Sensor CQ treated with Cu2+ can be applied to sequentialy detect cyanide anion.A new quinoline-based chemosensor (CQ) for sequential detection of Cu2+ and CN− has been synthesized, where diaminomaleonitrile is introduced as recognition group. After addition of Cu2+, sensor CQ in aqueous solution (DMSO/H2O) displays remarkable colorimetric change from the light yellow to red, which is attributed to the extended intermolecular charge transfer in CQ-Cu2+complex. Sensor CQ shows a highly selective and sensitive response to Cu2+, which can be used as Test strips to conveniently monitor Cu2+. In addition, CQ-Cu2+complex could be applied to monitor sequentially cyanide anion with dramatic colour change based on copper ion complex displacement mechanism.Download high-res image (215KB)Download full-size image

•Good functional group compatibility.•Stable and available starting materials.•The products can be serviceable building blocks.An efficient one-pot protocol for the synthesis of functionalized thiophene and benzo[b]thiophene derivatives was developed via a sequence of propargyl–allenyl isomerization/cyclization/demethylation. As a result of the readily accessible starting materials, simple operation, and mild conditions, this reaction should have potential utility in organic synthesis.

Acene derivatives as a class of polycyclic aromatic hydrocarbons have attracted considerable interest because of their outstanding semiconductor properties. We developed a one-pot synthesis for fully conjugated tetraphene via a sequence of propargyl-allenyl isomerization, phosphine addition, intramolecular Wittig reactions, and Diels–Alder cyclization reactions. The derivative-conjugated aromatic compounds including carbazole or triphenylamine have been constructed via Pd-catalyzed coupling reaction with dibromotetraphene. These compounds show superior photophysical and electrochemical properties, which make them possible candidates for optoelectronic conjugated materials.

An efficient metal-free procedure for the synthesis of 4-diphenylphosphoryl)methyl-2,3-dihydro-1H-pyrroles and furans was developed via a sequence of propargyl–allenyl isomerization and Alder ene reaction. The Wittig-type olefination transformation of the phosphine oxide moiety to the vinyl group with high stereoselectivity was further investigated.

Polycyclic skeletons are present in numerous important compounds, such as synthetic intermediates and target molecules of biological interest. In this paper, a Selectfluor-promoted construction of polycyclic skeletons with high synthetic efficiency was developed.

The synthesis of polysubstituted oxazolines is of great interest due to the synthetic and pharmaceutical importance. We developed a sequence of Pummerer/Michael reactions for the stereoselective synthesis of 5-(1-(arylthio)vinyl)-oxazolines.

Allenylphosphonium species, reactive Michael acceptors, could be generated from simple, readily available propargylphosphonium salts through propargyl–allenyl isomerization. We developed an efficient synthesis for cyclopentenes, pyrroles, and thiophenes via a sequence of propargyl–allenyl isomerizations, Michael additions, and intramolecular Wittig reactions.

Quinoline derivatives are important heterocyclic compounds because of their natural occurrence and applications in pharmaceutical fields. In this paper, a sequence of propargyl–allenyl isomerization and aza-electrocyclization for the synthesis of polyfunctionalized quinolines are described.

Construction of a new benzene via the electrocyclization of diene–allene is an efficient protocol to access polysubstituted benzenes from simple, readily available starting materials. In this paper, we present a comprehensive study of a heteroatom-promoted propargyl–allenyl isomerization and electrocyclization for the facile and efficient synthesis of polyfunctionalized benzenes and naphthalenes. As a result of the readily accessible starting materials, simple operation, and mild conditions, this reaction should be an appealing strategy in organic synthesis.

A sulfur-assisted five-cascade sequential reaction, wherein the in situ-generated allenyl allyl sulfides undergo thio-Claisen rearrangement, intramolecular Michael addition, and 1, 5-proton migration/aromatization to obtain allyl thiophen-2-yl acetates, propionates, and ketones as the final products, was reported. As a result of the ready availability of starting materials and the extremely simple and convenient operation, this type of reaction presented here has potential utility in organic synthesis. Application of this efficient method for the synthesis of potentially pharmaceutical compounds also might be useful for the pharmacists.

A facile and efficient electrocyclization for the synthesis of polyfunctionalized benzene and naphthalene derivatives was reported. As a result of the ready availability of starting materials and simple operation, this type of reaction has potential utility in organic synthesis.

A facile and efficient cyclization for the synthesis of tricyclic thiophene derivatives was developed. As a metal-free process, a result of the ready availability of the starting materials and the simple and convenient operation, the type of reaction presented here has potential utility in organic synthesis.

The regioselective dibromohydration of N-(2-alkynylaryl)acetamide with the participation of a neighbouring acetamino group is described here for the synthesis of N-(2-(2,2-dibromo-2-arylacetyl)aryl)acetamide. The dibromohydration proceeds under mild conditions and works well without metal catalysis. More importantly, by employing different neighbouring groups, switchable synthesis can be achieved. The entire process of the dibromohydration of N-(2-alkynylaryl)acetamide consists of KBr/K2S2O8-based electrophilic 6-exo cyclization to form bromo-containing benzoxazine cation and the oxidative ring-opening of the resulting bromo-containing benzoxazine cation. Water serves as a reagent to be incorporated into the acetamino group.

β-Sulfonium carbanions, members of the organosulfur family, are ephemeral intermediates and difficult to apply in organic syntheses. We developed a new strategy toward relatively stable β-sulfonium carbanions, achieved by an intramolecular addition of the sulfur atom of a sulfide to the in situ generated electron-deficient allene moiety. These types of applicable β-sulfonium carbanions may indicate an unexplored area in which a bundle of synthetically useful building blocks are yet to be discovered.

A facile synthesis of thiepine sulfones is described. It relies on a sequence of Rh(III)-catalyzed C–H cleavage, 1,5-H shift, and intramolecular allene insertion. As a result of extremely readily accessible starting materials and convenient operation, this protocol should be an appealing strategy in organic synthesis.

The regioselective dibromohydration of N-(2-alkynylaryl)acetamide with the participation of a neighbouring acetamino group is described here for the synthesis of N-(2-(2,2-dibromo-2-arylacetyl)aryl)acetamide. The dibromohydration proceeds under mild conditions and works well without metal catalysis. More importantly, by employing different neighbouring groups, switchable synthesis can be achieved. The entire process of the dibromohydration of N-(2-alkynylaryl)acetamide consists of KBr/K2S2O8-based electrophilic 6-exo cyclization to form bromo-containing benzoxazine cation and the oxidative ring-opening of the resulting bromo-containing benzoxazine cation. Water serves as a reagent to be incorporated into the acetamino group.