The "cation pool" of an N-acyliminium ion was found to serve as an effective initiator of cationic polymerization of vinyl ethers in a microsystem consisting of two micromixers and a microtube reactor. The polymerization led to very narrow molecular weight distribution (Mw/Mn = 1.14). The molecular weight (Mn) increased linearly with an increase in the amount of the monomer. The carbocationic polymer end was effectively trapped by allyltrimethylsilane. The present observations illustrate the potential of microsystems, in conjunction with the cation pool, to effect polymerization in a highly controlled manner without the deceleration inherent in the dynamic equilibrium between active and dormant species.

[reaction: see text] Alkoxycarbenium ions have been generated and accumulated as "cation pools" by the low-temperature electrochemical oxidation of alpha-phenylthioethers. Although an unsuccessful attempt to accumulate glycosyl cations was made, a one-pot method for electrochemical glycosylation, which involves anodic oxidation of thioglycosides to generate glycosyl cation equivalents followed by their reactions with glycosyl acceptors, has been developed.

A "cation pool" of an N- acyliminium ion was found to serve as an effective initiator of cationic polymerization of vinyl ethers in a microflow system consisting of two micromixers (IMM micromixer) and two microtube reactors. The cationic polymerization of n-butyl vinyl ether in CH(2)Cl(2) at -78 degrees C led to very narrow molecular weight distribution (M(w)/M(n)=1.14). The molecular weight (M(n)) increased linearly with an increase in monomer/initiator ratio. The carbocationic polymer end was effectively trapped by allyltrimethylsilane. Additionally, the synthesis of block polymers was accomplished by the present microflow system controlled method. The polymerization was also conducted using commercially available trifluoromethanesulfonic acid (TfOH) as an initiator. A high level of molecular weight control was attained even at -25 degrees C. The TfOH-initiated polymerization could be conducted using a microflow system based on T-shaped micromixers, which serves as a practical tool for microflow system controlled carbocationic polymerization.

Intermediates O 0190Generation of Alkoxycarbenium Ion Pools from Thioacetals and Applications to Glycosylation Chemistry. -The title ions are generated by low-temperature electrochemical oxidation of α-phenylthioethers. Attempts to detect the ion pools under these conditions fail. High β-selectivity is observed for the one-pot method using Bu4NClO4, whereas the corresponding in situ method (electrochemical reaction in the presence of a glycosyl acceptor using Bu 4 NB(C 6 F 5 ) 4 ) exhibits α preference. -(SUZUKI, S.; MATSUMOTO, K.; KAWAMURA, K.; SUGA*, S.; YOSHIDA*, J.-I.; Org. Lett. 6 (2004) 21, 3755-3758; Dep. Synth. Chem. Biol Chem., Grad. Sch. Eng., Kyoto Univ., Nishikyo, Kyoto 615, Japan; Eng.) -Steudel 04-041