Metal-Free Electrophilic Phosphination/Cyclization of Alkynes

A metal-free electrophilic phos­phin­ation reaction has been developed. Electro­philic phosphorus species generated <i>in situ</i> from secondary phos­phine oxides and Tf₂O smoothly couple with alkynes possessing pendant nucleo­philes to afford the corresponding phos­phin­ated cyclization products in good yield. Preliminary NMR studies show that phos­phir­enium species may be involved as inter­mediates of the cyclization reactions

Rhodium(III)-catalyzed Oxidative Coupling through C–H Bond Cleavage Directed by Phosphinoxy Groups

A straightforward synthesis of phosphaisocoumarins is achieved by the rhodium-catalyzed oxidative coupling of diarylphosphinic and phenylphosphonic acid derivatives with alkynes. The P–OH groups effectively act as the key function for the regioselective C–H bond cleavage. Related oxidative coupling of phenylphosphine oxides with alkenes can also be conducted smoothly under similar conditions

Rhodium(III)-Catalyzed Direct Coupling of Arylphosphine Derivatives with Heterobicyclic Alkenes: A Concise Route to Biarylphosphines and Dibenzophosphole Derivatives

The redox-neutral direct coupling of arylphosphine oxides with heterobicyclic alkenes proceeds smoothly under rhodium­(III) catalysis involving hydroarylation followed by dehydrative aromatization to form biarylphosphine oxides. Related phenylphosphinic and phenylphosphonic esters as well as phenylphosphine sulfides also undergo ortho-arylative coupling. Furthermore, phenylphosphinothioic amides can be transformed to fused dibenzophosphole derivatives through rhodium-catalyzed coupling with heterobicyclic alkenes and successive intramolecular phospha-Friedel–Crafts reaction in a one-pot manner

Rhodium(III)-Catalyzed Oxidative Alkenylation of 1,3-Dithiane-Protected Arenecarbaldehydes via Regioselective C–H Bond Cleavage

A Rh­(III)-catalyzed direct alkenylation of 2-aryl-1,3-dithiane derivatives with alkenes has been developed. The 1,3-dithiane group can serve as an effective directing group for the exclusively monoselective alkenylation under mild oxidative conditions. The directing group is readily removable after the coupling event

Regioselective Synthesis of Benzo[<i>b</i>]phosphole Derivatives via Direct <i>ortho</i>-Alkenylation and Cyclization of Arylthiophosphinamides

A new regioselective synthetic methodology for benzo­[<i>b</i>]­phosphole derivatives has been developed. Thus, a range of functionalized benzo­[<i>b</i>]­phosphole oxides could be synthesized via Rh­(III)-catalyzed C–H alkenylation of arylthiophosphinamides with alkynes followed by formal phospha-Friedel–Crafts cyclization

Rhodium(III)-Catalyzed Regioselective C–H Alkenylation of Phenylphosphine Sulfides

The regioselective alkenylation at the <i>ortho</i> position of phenylphosphine sulfides using alkenes proceeds efficiently in the presence of a cationic Cp*-rhodium­(III) catalyst and an appropriate oxidant. A similar rhodium catalyst also promotes the redox-neutral coupling of the phosphine sulfides with alkynes to afford <i>ortho</i>-alkenylated products

Synthesis of Benzo[<i>c</i>]thiophenes by Rhodium(III)-Catalyzed Dehydrogenative Annulation

The dehydrogenative annulation of thiophen-2-carboxamides with 2 equiv of alkynes proceeds efficiently in the presence of a rhodium catalyst and a copper oxidant to furnish multiply substituted benzo­[<i>c</i>]­thiophenes. Some of the synthesized benzo­[<i>c</i>]­thiophenes exhibited strong solid-state fluorescence