Behavior of 1,1-diphenyl-2,5-dihydrophospholium salts toward bases: Ylide formation or ring opening

✍ Scribed by Henri-Jean Cristau; Jerome Grenier; Patricia Lezouret; Eliane Torreilles

• Book ID: 102655405
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 877 KB
• Volume: 7
• Category: Article
• ISSN: 1042-7163
• DOI: 10.1002/(sici)1098-1071(199611)7:6<471::aid-hc10>3.0.co;2-n

✦ Synopsis

Eficient procedures are described leading to pure 3,4-R', R2-substituted I , l-diphenyl-2,5-dihydrophospholium salts (R' = R2 = CH,, H; R' = CH,, R2 = H). Their behaviors toward bases such as nBuLi and t- BuOK in THF or DMSO have been examined. According to the nature of the substituents R' and R2, the complete monodeprotonation of these salts leads either to the corresponding pure five-membered cyclic ylide (and, in some cases, its prototropic isomer) or to a dienylphosphine resulting from a ring opening. The reactivity of the 3,4-dimethyl-disubstituted salt was especially studied. The corresponding monoylide functions as a good Wittig reagent, allowing stereoselective access to interesting alkadienylphosphine oxides and subsequentlv to trienes. However, in the presence of alkylating electrophiks, it reacts under an open dienylphosphine form giving rise to P-alkylated phosphonium salts. Nevertheless, this monoylide does not undergo further deprotonation into the corresponding cyclic diylide. Most of the synthetisized derivatives are original. 0 I996 John Wiley & Sons, Inc.