Metathesis Reactions for the Synthesis of Ring-Fused Carbazoles

• Published in: Journal of organic chemistry Vol. 70; no. 25; pp. 10474 - 10481
• Main Authors: Pelly, Stephen C, Parkinson, Christopher J, van Otterlo, Willem A. L, de Koning, Charles B
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 09.12.2005; Amer Chemical Soc
• Subjects: Carbazoles - chemical synthesis; Chemistry; Chemistry, Organic; Cyclization; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with n hetero atom and also o and/or s, se, te hetero atoms; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Indoles - chemical synthesis; Magnetic Resonance Spectroscopy; Organic chemistry; Physical Sciences; Preparations and properties; Science & Technology; ORGANIC-SYNTHESIS; INDOLOCARBAZOLES; TRANSITION-METAL-COMPLEXES; MURRAYAQUINONE; BIOLOGICAL EVALUATION; TOPOISOMERASE-I; OLEFIN METATHESIS; CLOSING METATHESIS; CONCISE SYNTHESIS; REBECCAMYCIN; Chemical synthesis; Nitrogen heterocycle; Carbazole derivatives; Metathesis
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo051826s

The metathesis reaction is used as a key step for the synthesis of the indolo[2,3-a]carbazole core of rebeccamycin 13 and the sulfur analog of furostifoline 21. Using the same methodology for the attempted synthesis of furostifoline, we unexpectedly formed tert-butyl-2a-methyl-1,2,2a,10c-tetrahydro-6H-cyclobuta[c]furo[3,2-a]carbazole-6-carboxylate 26 from the unstable diene, tert-butyl 2-(2-isopropenyl-3-furyl)-3-vinyl-1H-indole-1-carboxylate 25, presumably via a spontaneous π8 electrocyclization reaction.