Unexpected aspect of the Fischer indolization of propiophenone (5-chloro-2-methoxyphenyl)hydrazone

2011 ◽  
Vol 21 (6) ◽  
pp. 337-338 ◽  
Author(s):  
Galina V. Kokurkina ◽  
Mikhail D. Dutov ◽  
Svyatoslav A. Shevelev ◽  
Vadim V. Kachala ◽  
Alexander O. Chizhov ◽  
...  
Keyword(s):  
Fischer Indolization

ChemInform Abstract: Synthesis of Enantiopure (2R,3aS,7aS)-2-Ethyloctahydroindol-6-one and Its Fischer Indolization.

ChemInform ◽  
2010 ◽  
Vol 29 (6) ◽  
pp. no-no
Author(s):  
J. BONJOCH ◽  
J. CATENA ◽  
D. TERRICABRAS ◽  
J.-C. FERNANDEZ ◽  
M. LOPEZ-CANET ◽  
...  
Keyword(s):  
Fischer Indolization

scholarly journals Design and synthesis of hybrid cyclophanes containing thiophene and indole units via Grignard reaction, Fischer indolization and ring-closing metathesis as key steps

2015 ◽  
Vol 11 ◽  
pp. 1514-1519 ◽  
Author(s):  
Sambasivarao Kotha ◽  
Ajay Kumar Chinnam ◽  
Mukesh Eknathrao Shirbhate
Keyword(s):  
Grignard Reaction ◽  
Ring Closing Metathesis ◽  
Design And Synthesis ◽  
Synthetic Strategy ◽  
Fischer Indolization ◽  
Grignard Addition ◽  
Key Steps

We demonstrate a new synthetic strategy to cyclophanes containing thiophene and indole moieties via Grignard addition, Fischer indolization and ring-closing metathesis as key steps.

Synthesis of tricyclic units of indole alkaloids: Application of Fischer indolization and olefin metathesis

Tetrahedron ◽  
2017 ◽  
Vol 73 (45) ◽  
pp. 6436-6442 ◽  
Author(s):  
Sambasivarao Kotha ◽  
Vikas R. Aswar ◽  
Gaurav Singhal
Keyword(s):  
Olefin Metathesis ◽  
Indole Alkaloids ◽  
Fischer Indolization

scholarly journals A Fischer Indolization Strategy toward the Total Synthesis of (–)-Goniomitine

Heterocycles ◽  
2017 ◽  
Vol 95 (2) ◽  
pp. 1245 ◽  
Author(s):  
Brian M. Stoltz ◽  
Beau P. Pritchett ◽  
Jun Kikuchi ◽  
Yoshitaka Numajiri
Keyword(s):  
Total Synthesis ◽  
Fischer Indolization

The Garg Synthesis of (±)-Aspidophylline A

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Drug Resistance ◽  
Trifluoroacetic Acid ◽  
Keto Ester ◽  
Heck Cyclization ◽  
Final Assembly ◽  
Fischer Indolization ◽  
Perceived Difficulty ◽  
Bicyclic Ketones ◽  
Terminal Alkene ◽  
Allyl Iodide

The pentacyclic Apocynaceae alkaloid aspidophylline A 3 reverses drug resistance in resistant KB cells. In developing a strategy for the assembly of 3, Neil K. Garg of UCLA envisioned (J. Am. Chem. Soc. 2011, 133, 8877) the intramolecular Pd-catalyzed cyclization of 1 to 2. The starting material for the cyclohexenone derivative 1 was the known tricyclic anhydride 7. This was readily available in gram quantities by oxidation of the commercial pyridone 4. The double decarboxylation to 8 was delicate but could be effected by iterative small-batch microwave heating. Protection of 8 followed by fragmentation and alkylation than delivered 1. The intramolecular Heck cyclization of 1 indeed proceeded smoothly, giving the bicyclic diene 2. Deprotection of the ketone revealed a doubly activated enone, which could be selectively reduced under modifi ed dissolving metal conditions to give the keto ester 12. Alkylation of the lithium enolate with allyl iodide then gave 13, predominantly as the diastereomer illustrated. Reduction followed by selective Johnson-Lemieux oxidative cleavage of the terminal alkene then completed the construction of the diol 14. The vision for the final assembly of the alkaloid was to effect interrupted Fischer indolization of an alkylated cyclohexanone such as 15. To this end, several bicyclic ketones were explored, but none was successful. Finally, attention was turned to the more rigid tricyclic lactone 15. Happily, exposure of 15 to phenylhydrazine in the presence of trifluoroacetic acid led to an intermediate that was not isolated, but directly combined with methanolic K2CO3 to open the lactone, allowing closure of the tetrahydrofuran ring, to give 16. Simple arene sulfonamides can be advantageous in synthesis, as they do not appear as rotameric mixtures in NMR, and are often crystalline. Nevertheless, they have not commonly been used because of the perceived difficulty of deprotection. Sonication of 16 with Mg powder in methanol containing solid NH4Cl led to smooth desulfonylation. Formylation then completed the synthesis of aspidophylline A 3.

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