Free and Polymer-Bound Tricyclic Azaphosphatranes HP(RNCH(2)CH(2))(3)N(+): Procatalysts in Dehydrohalogenations and...

The commercially available nonionic base P(CH(3)NCH(2)CH(2))(3)N (1a) was shown earlier to be superior to DBU as a stoichiometric reagent for the conversion of primary and secondary alkyl halides to alkenes (Arumugam, S.; Verkade, J. G. J. Org. Chem. 1997, 62, 4827). The precursor cation HP(CH(3)NCH(2)CH(2))(3)N(+) (2) to 1a, which is more stable and less expensive, is reported herein to be an efficient procatalyst for these reactions and also for the debromination of vicinal dibromides using NaH as a relatively inexpensive stoichiometric hydride source in CH(3)CN at room temperature. In dehydrohalogenations requiring more than ca. 10 h, the CH(2)CN(-) ion also acts as a base. By itself, NaH does not function well or at all under the same conditions. A catalytic cycle is proposed in which hydride deprotonates cation 2 liberating catalytic 1a. The cations HP(HNCH(2)CH(2))(3)N(+) (3) and HP[N(polymer)CH(2)CH(2)]N(CH(2)CH(2)NH)(2)(+) (4) are also shown to function as procatalysts for the efficient dehydrohalogenation of RX and for the debromination of vicinal dibromides. The preparation of the heterogeneous procatalyst 4(OTf) is also described.