- Bismuth(III) Triflate Catalyzed Three-Component Reactions of Indoles, Ketones, and α-Bromoacetaldehyde Acetals Enable Indole-to-Carbazole Transformation
-
A three-component reaction of indoles, α-bromoacetaldehyde acetals, and ketones was developed by using bismuth(III) triflate as the catalyst to realize a straightforward approach for synthesizing carbazole derivatives. The reaction was established mechanistically through the autotandem catalysis of Bi(OTf)3 in the following two steps: (i) Friedel-Crafts-type alkylation of indole with α-bromoacetaldehyde acetal, which produced a tryptaldehyde-type intermediate and (ii) [4 + 2] annulation of this intermediate with the ketone component.
- Gu, Yanlong,Huang, Wenbo,Chen, Shaomin,Wang, Xin
-
supporting information
p. 4285 - 4289
(2018/07/29)
-
- Syntheses of Carprofen, A Carbazole-Based Nonsteroidal Anti-Inflammatory Agent
-
Syntheses of carprofen (6) have been achieved by two approaches from carbazole (11).In one, 2,9-diacetylcarbazole (12) and 2-acetylcarbazole (13) were chlorinated with trichloroisocyanuric acid (15) to give the 6-chloro derivatives (16) and (17), respectively.Reduction of 16 with NaBH4, followed by acetylation, cyanide displacement, and hydrolysis afforded 6 in 73percent yield from 16.Alternatively, 17 was converted into its trimethylsilyloxy cyanohydrin derivative (27), which was reduced with SnCl2 and hydrolysed to give 6 in 75percent yield from 17.In the other approach, the ketone (18), derived by a Friedel-Crafts acylation of 9-acetylcarbazole with 2-chloropropanoyl chloride followed by chlorination with 15, was converted into the hydroxyketal (28) with methanolic NaOMe.Mesylation of 28, followed by a modified Favorskii rearrangement and hydrolysis gave 6 in 73percent yield from 18.
- Manchand, Percy S.,Coffen, David L.,Belica, Peter S.,Wong, Frederick,Wong, Harry S.,Berger, Leo
-
p. 833 - 846
(2007/10/02)
-
