Selective Surface Decoration of Corannulene

The reaction of corannulene (C20H10) with
1,2-C2H4Hal2 (Hal = Cl or Br) in
the presence of AlCl3 affords stable nonplanar carbocations
C20H10CH2CH2Hal+ (Hal = Cl (1) and Br (2)) with an −CH2CH2Hal moiety attached to the interior carbon atom
of the bowl. In the analogous reaction with 1-bromo-2-chloroethane,
the selective (up to 98%) abstraction of chloride is observed with
the formation of cation 2. The molecular structures of
bowl-shaped carbocations 1 and 2 crystallized
as salts with AlCl4– counterions are
revealed by single-crystal X-ray diffraction. The reaction of 2 with methanol or ethanol provides further decoration of
the nonplanar polyarene upon the nucleophilic addition of alkoxy groups
to the exterior carbon atom of the corannulene moiety. The 1H NMR investigation of the corresponding products, C20H10(CH2CH2Br)­(OCH2R)
(R = H (3) and CH3 (4)), shows
the formation of intramolecular H···O and H···Br
hydrogen bonds.