14192-51-9Relevant articles and documents
Total Synthesis of Marine Alkaloid Hyellazole and its Derivatives
Chakraborty, Suchandra,Saha, Chandan
, p. 2013 - 2021 (2018/05/15)
The total synthesis of the naturally occurring marine alkaloids hyellazole and chlorohyellazole was attempted from the corresponding easily accessible 2-methyl-1-ketotetrahydrocarbazoles obtained through the Japp–Klingemann reaction, followed by Fischer indole cyclization and subsequent Grignard coupling with phenylmagnesium bromide. Grignard coupling with 2-methyl-1-ketotetrahydrocarbazole unfortunately led directly to 2-methyl-1-phenylcarbazole through dehydration followed by aromatization through aerial oxidation, but application of the same reaction conditions to 6-chloro-2-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one, with careful treatment, led to the isolation of 6-chloro-2-methyl-1-phenyl-4,9-dihydro-3H-carbazole. However, selenium dioxide oxidation of this dihydrochloro derivative led to the formation of 6-chloro-2-methyl-1-phenyl-9H-carbazole. A different route was then adopted: a suitably substituted aromatic amine was used to establish the substitution pattern of the required carbazole derivative with a bromo group at C-1, and the required phenyl group at the 1-postion was then attached through Suzuki–Miyaura cross-coupling to furnish hyellazole.
A novel CAN-SiO2-mediated one-pot oxidation of 1-keto-1,2,3,4-tetrahydrocarbazoles to carbazoloquinones: Efficient syntheses of murrayaquinone A and koeniginequinone A
Chakraborty, Suchandra,Chattopadhyay, Gautam,Saha, Chandan
scheme or table, p. 331 - 338 (2011/06/19)
One-pot oxidations of substituted 1-keto-1,2,3,4-tetrahydrocarbazoles (1) to carbazole-1,4-quinones (2) are efficiently carried out by CAN-SiO 2-mediated reaction. This generalized protocol was successfully extended to the synthesis of two naturally occurring carbazoloquinones: murrayaquinone A (2b) and koeniginequinone A (2g). A plausible mechanism for this novel reaction involves formation of a 9-hydroxy-2,3,4,9-tetrahydro-1H- carbazole-1-one followed by rearrangement to 1-hydroxycarbazole derivatives, which are further oxidized by cerium (IV) to carbazoloquinones.
