| Research Abstract |
Benzo[ b, d] furan, benzo[ b] naphtho[ 1, 2-d] furan, benzo[ b] naphtho[ 2, 3-d] furan, benzo[ b] naphtho-[ 2, 1-d] furan, dinaphtho[ 2, 1-b : 1', 2'-d] furan, benzo[ b] naphtho[ 1, 8-de] pyran, dibenzo[ d, d'] benzo-[ 1, 2-b : 4, 3-b'] difuran, dibenzo[ d, d'] benzo[ 1, 2-b : 4, 5-b'] difuran, naphtho[ 2, 1-b : 3, 4-b'] bisbenzofuran, benzo[ 2, 3][ 1] benzofuro[ 4, 5, 6-kl] xanthene, and 9, 9-dimethyl-9H-9-silafluorene were synthesized. Their reactions in superacid/SO2ClF gave protonated carbocations, which were directly observed by NMR at low temperatures. NMR analysis and DFT calculations indicate that positive charges are delocalized into limited rings substituted by oxygen atoms.
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