Anchimer beschleunigte Homolysen

11 12 f a h 1 -Cx&-pCH3 -I OH 13 Scheme 4. a) I . EtMgBr, Cul, Me,S, THF; 2. H,C=CHCH,Br, hexamethylphosphoric acid triamide (HMPT) (60%); b) NaH, glyme, HCOOEt (95%); c) PhN,CI ( 8 5 % ) ; d) HCOOH (86%); e) NaOMe, MeOH, RT, 12-14d (99%); f) I . OsO,, NaIO,, MTBE, H,O; 2. MeNHOH, NaCNBH,, iPrOH, pH = 6 (85%); gj MeLi, THF, -20°C + RT (98%); hj Ac,O, pyridine, 3 h, RT (99%).carbazole derivative 1 is achieved by the addition of methyllithium to the carbonyl function, and 0-acetylization of the hydroxylamine group.['] The conversion of 13 to uleine (2) can be performed in good yields without chromatographic purification of the intermediates. The novel cascade reaction allows the application of the readily obtained trans configuration of the tetrahydrocarbazole 13 for a concise and stereoselective synthesis of uleine. This example demonstrates once more that the application of domino processes can open more efficient and shorter synthetic pathways. Experimental Section2: Tetrahydrocarhazole l(68.8 mg, 0.2 mmol) was dissolved in formic acid ( 5 mLj and left at room temperature for 15 min. The solvent was evaporated under reduced pressure and the crude product was purified by preparative thin-layer chromatography (silica1 gel, CH,CI,/MeOH, 95/5 under NH, atmosphere) to give (k)-uleine (2) (54 mg, 95 %)

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Anchimer beschleunigte Homolysen

Cited by 8 publications

References 44 publications

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Relative Wanderungsneigung von Substituenten und Stereochemie der dyotropen Ringerweiterung von β‐Lactonen

Relative Migratory Aptitude of Substituents and Stereochemistry of Dyotropic Ring Enlargements of β‐Lactones

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