Bifunctionalized Allenes. Part XVI. Synthesis of 3-Phosphoryl-2,5-dihydrofurans by Coinage Metal-Catalyzed Cyclo-isomerization of Phosphorylated α-Hydroxyallenes

Abstract

Phosphorylated α-hydroxyallenes 1 and 2 were smoothly converted into the corresponding 2,5-dihydrofurans 3 and 4 in an 5-endo-trig cycloisomerization reaction by using 5 mol % of coinage metal salts as catalyst. Experimental conditions such as the type of the solvent, the reaction temperature, the mol % and the type of the catalyst were optimized. This mild and efficient cyclization method can be applied to dimethyl 1-hydroxyalkyl-alka-1,2-dienephosphonates 1 and 2-diphenylphosphinoyl-2,3-dien-1-ols 2a–c and 3-diphenylphosphinoyl-3,4-dien-2-ols 2d,e, furnishing 3-phosphorylated 2,5-dihydrofurans 3 and 4 in very good yields.

Palladium‐Catalyzed Cascade C−O Cleavage and C−H Alkenylation of Phosphinyl Allenes: An Expeditious Approach to 3‐Alkenyl Benzo[b]phosphole Oxides

“…Substrates bearing aromatic substitutions showed comparable reactivities with excellent yields (Table , entries 1–4), whereas an alkyl one performed sluggishly under the standard conditions, with only 10% yield of target product formed (entry 5). In terms of substitution‐free substrate ( α ‐allenic alcohol, R=H), a dihydrofuranyl derivative ( I ) was isolated instead of 3‐alkenyl benzo[ b ]phosphole oxides (entry 6), resulting from the nucleophilic attack of hydroxyl group to palladium‐allene complex. Notably, most of the purified allene substrates were highly viscous gum, therefore 2,6‐dimethylphenyl substituted allenes were chosen for further studies due to their crystalline state and operationally simplicity.…”