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. 2019 Jul 9:15:1515-1520.
doi: 10.3762/bjoc.15.153. eCollection 2019.

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

Sean H Kennedy  1 , Makafui Gasonoo  1 , Douglas A Klumpp  1
Affiliations

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

Sean H Kennedy et al. Beilstein J Org Chem. .

Abstract

A substrate has been prepared having two triarylmethanol centers and four pyridine-type substituent groups. Upon ionization in the Brønsted superacid CF3SO3H, the substrate undergoes two types of reactions. In the presence of only the superacid, the highly ionized intermediate(s) provide a double cyclization product having two pyrido[1,2-a]indole rings. With added benzene, an arylation product is obtained. A mechanism is proposed involving tetra-, penta-, or hexacationic species.

Keywords: Friedel–Crafts; cation; heterocycle; superacid; superelectrophile.

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Figures

Scheme 1
Scheme 1
Superelectrophilic species.
Scheme 2
Scheme 2
Synthesis of diol substrate 9.
Scheme 3
Scheme 3
Isolated yields of products from diol 9.
Scheme 4
Scheme 4
Proposed mechanisms leading to products 10 and 11.
Scheme 5
Scheme 5
Products and relative yields from the reaction of alcohol 18 with CF3SO3H and C6H6 [12].
Scheme 6
Scheme 6
Comparison of superelectrophilic carbocations (3–5 and 14) and their chemistry.
Scheme 7
Scheme 7
DFT calculated relative energies of pentacations 16 and 21 [14].
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