Studies in the protection of pyrrole and indole derivatives

Abstract

Treatment of pyrrole (1a), 2,5-dimethylpyrrole (1b), indole (3a), 2-methylindole (3b), 3-methylindole (3c), 2,3-dimethylindole (3d), 1,2,3,4-tetrahydro-9H-carbazole (5a), 5,6,7,8,9,10-hexahydro-cyclohept[b]indole (5b), and 6,7,8,9,10,11-hexahydro-5H-cyclo-oct[b]indole (5c) with sodium hydride in tetrahydrofuran, followed by phenyl t-butyl carbonate (8) gives the corresponding N-t-butoxycarbonyl (t-BOC) derivatives [(2a), (2b), (4a), (4b), (4c), (4d), (6a), (6b), and (6c), respectively] in satisfactory yields. By using chlorodimethyl-t-butylsilane instead of (8), N-dimethyl-t- butylsilyl derivatives [(10a), (10b), (11a), (11b), (11c), (11d), (12a), and (12b)] are obtained, also in satisfactory yields. The use of the 2-(trimethylsilyl)ethoxycarbonyl (TEOC) group for the N-protection of the indole system, and the pivaloyloxymethyl (POM) group for the N-protection of the pyrrole and indole systems is also described.