Phosphaannulation by Palladium-Catalyzed Carbonylation of C–H Bonds of Phosphonic and Phosphinic Acids

An efficient phosphaannulation by Pd-catalyzed carbonylation of C–H bonds of phosphonic and phosphinic acids for the synthesis of oxaphosphorinanone oxides is reported. These compounds are novel phosphorus heterocyclic scaffolds, thus opening a new avenue to sequential C–C/C–O bond formation in one pot

Ruthenium-Catalyzed C–H Activation/Cyclization for the Synthesis of Phosphaisocoumarins

An efficient and cost-effective ruthenium-catalyzed oxidative cyclization of phosphonic acid monoesters or phosphinic acids with alkynes has been developed for the synthesis of a wide range of phosphaisocoumarins in good to excellent yields under aerobic conditions. A multitude of arylphosphonic acid monoesters and arylphosphinic acids having electron-donating and -withdrawing groups were oxidatively cyclized. Various diarylacetylenes, dialkylacetylenes, and alkylarylacetylenes effectively underwent the ruthenium-catalyzed oxidative cyclization. A substrate possessing benzoic acid as well as a phenylphosphonic monoester moiety was smoothly cyclized with hex-3-yne to afford a compound having both isocoumarin and phosphaisocoumarin moieties. Alkenylphosphonic monoester afforded phosphorus 2-pyrone through oxidative cyclization with alkyne. Competition experiments between diaryl- and dialkylalkynes and between diarylacetylenes having <i>p</i>-methoxy and <i>p</i>-chloro groups gave results which showed that the present oxidative cyclizations were not affected by the electronic effects of alkynes. Mechanistic studies revealed C–H bond metalation to be the rate-limiting step

Synthesis of Multisubstituted Allenes, Furans, and Pyrroles via Tandem Palladium-Catalyzed Substitution and Cycloisomerization

A palladium-catalyzed propargyl substitution reaction of propargyl acetates with indium organothiolates is developed for the synthesis of multisubstituted allenyl sulfides. This procedure can be applied to the synthesis of multisubstituted furans and pyrroles via tandem palladium-catalyzed propargyl substitution and cycloisomerization reaction in one pot

Alkenylation of Phosphacoumarins via Aerobic Oxidative Heck Reactions and Their Synthetic Application to Fluorescent Benzo­phospha­coumarins

Alkenylation of phosphacoumarins is developed from the reaction of phosphacoumarins with a variety of activated as well as nonactivated alkenes via aerobic oxidative Heck reactions. In addition, 3-alkenyl­phospha­coumarins undergo an inverse electron demand Diels–Alder reaction (IEDDA) with enamines <i>in situ</i> generated from ketone and pyrrolidine followed by 1,2-elimination and a dehydrogenation, producing fluorescent benzo­phospha­coumarins

Synthesis of 2‑Alkoxyaryl-2-aryl Enamines via Tandem Copper-Catalyzed Cycloaddition and Rhodium-Catalyzed Alkoxyarylation from Alkynes, <i>N</i>‑Sulfonyl Azides, and Aryl Ethers

A synthetic route to a wide range of 2-alkoxyaryl-2-aryl enamines is developed from Rh-catalyzed alkoxyarylation of <i>N</i>-sulfonyl-4-aryl-1,2,3-triazoles with aryl ethers via the elimination of nitrogen molecule. In addition, 2-alkoxyaryl-2-aryl enamines are prepared via tandem Cu-catalyzed cycloaddition and Rh-catalyzed alkoxyarylation starting from alkynes, <i>N</i>-sulfonyl azides, and aryl ethers in one-pot