α-Allenyl Ethers as Starting Materials for Palladium Catalyzed Suzuki–Miyaura Couplings of Allenylphosphine Oxides with Arylboronic Acids

Abstract

We disclose here the first palladium-catalyzed Suzuki-Miyaura couplings of aryl ethers functionalized allenylphosphine oxides with arylboronic acids. This new methodology with α-allenyl ethers as starting materials provides a novel approach to generate phosphinoyl 1,3-butadienes and derivatives with medium to excellent yields. The reaction tolerates a variety of functional groups to afford ranges of structurally diverse substituted phosphionyl 1,3-butadienes. For unsymmetrical allene substrates, high stereospecific additions to give E-isomers are usually observed. On the basis of the known palladium and allene chemistry, a mechanism is proposed.

Palladium-Catalyzed Cleavage of α-Allenylic Aryl Ether toward Pyrazolemethylene-Substituted Phosphinyl Allenes and Their Transformations via Alkenyl C–P(O) Cleavage

“…Intriguingly, conjugated N -tosylhydrazones changed the coupling pathway against the formation of conjugated alkenes, as illustrated in Scheme d. In continuation of our interest in organophosphorus and heterocyclic chemistry, herein, we disclose a palladium-catalyzed cleavage of allenyl electron-rich functionality to finalize pyrazolemethylene-substituted phosphinyl allenes. The allene moiety is maintained in the palladium-catalysis system, offering the first synthesis of combined motifs with pyrazole and allene, to our knowledge .…”

Substituents Regulate the Cyclization of Conjugated Alkynes to Accurately Construct Cyclo-(E)-[3]dendralenes

“…Inspired by the aforementioned studies and our continuous work on allenyl-phosphine oxides [31][32][33][34][35][36][37], mechanistically, an ideal approach to access phosphinyl cyclic-(E)- [3]dendralenes can be an acid-catalyzed cyclization and substituent-regulated conjugation of alkynes (Scheme 2c).…”

Copper‐Catalyzed Allenylation‐Isomerization Sequence of Penta‐1,4‐diyn‐3‐yl Acetates with P(O)H Compounds: Facile Synthesis of 1‐Phosphonyl 2,4‐Diynes

“…The high demand for these compounds in cyclizations and related reactions for constructing structurally more sophisticated organophosphorus compounds consequently stimulates the development of alternative methods ,. A few synthetic methods for phosphonyl 1,3‐dienes have been recently reported based on the transformations of phosphonyl allenes –…”