A novel and convenient protocol for the
synthesis of hexahydroxy [2.1.2.1.2.1]- and octahydroxy
[2.1.2.1.2.1.2.1] metacyclophanes from 4-substituted phenol in
four steps has been developed. The synthetic route involved the
preparation of the key intermediate
1,2-bis(5-substituted-2-hydroxyphenyl) ethanes in good yields
via (i) formylation of 4-substituted phenol, (ii) reductive
deoxygenation of 5-substituted 2-hydroxy aromatic aldehydes with
low-valent titanium reagent and (iii) catalytic hydrogenation.
The metacyclophanes were prepared by base-catalyzed
macrocyclization of the above intermediates with formaldehyde in
refluxing xylene in high yields.
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