Diarylcarbenium ions generation

Scheme 5.23 Generation of diarylcarbenium ion pools by C—H bond dissociation...

Okajima M, Soga K, Nokami T et al (2006) Oxidative generation of diarylcarbenium ion pools. Org Lett 8 5005-5007... 

Okajima M, Soga K, Watanabe T et al (2009) Generation of diarylcarbenium ion pools via electrochemical C-H bond dissociation. Bull Chem Soc Jpn 82 594-599... 

Microsystem-controlled cationic polymerization technology requires extremely reactive initiators and cation pools serve as effective initiators for this technology. Usually carbocations are generated by a reversible process from their precursor. Yoshida et al. developed the cation pool method [35], in which carbocations are generated irreversibly by low-temperature electrolysis and are accumulated in relatively high concentration in the absence of nucleophiles. N-Acyliminium ions, alkoxycarbenium ions [36-40] and diarylcarbenium ions [41] have been generated by this method. Such cation pools are expected to serve as extremely reactive initiators for cationic polymerization. 

A report has described a route to multiply alkylated thiophene derivatives from electrochemically derived diarylcarbenium ions (Scheme 46). Using the cation-pool technique - in which the cationic intermediate is generated in high concentration and pooled - the carbocation (228) alkylates thiophene, providing up to 58% of the trialkylated product (229) and 24% of the dialkylated product (230). 

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