Selenium-catalyzed reductive cyclization and carbocyclization of 2,2′-dinitrostilbenes with carbon monoxide: One-shot synthesis of indolo[1,2-c]quinazolinones

2011 ◽  
Vol 22 (3-4) ◽  
pp. 571-575 ◽  
Author(s):  
Rui Umeda ◽  
Shigeru Morishita ◽  
Yutaka Nishiyama
Keyword(s):  
Carbon Monoxide ◽  
Reductive Cyclization

The Carreira Synthesis of (±)-Gelsemoxonine

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Carbon Monoxide ◽  
Aldol Condensation ◽  
Computational Study ◽  
Addition Product ◽  
Nitrile Oxide ◽  
Reductive Cyclization ◽  
Single Diastereomer ◽  
Open Face ◽  
Unsaturated Nitrile

The traditional Chinese pharmacopeia includes Gelsemium elegans benth, from which the alkaloid gelsemoxonine 3 was isolated. Erick M. Carreira of the Eidgenössische Technische Hochschule Zürich envisioned (J. Am. Chem. Soc. 2013, 135, 8500) that the unusual azetidine ring of 3 could be established by Brandi contraction of 1 to give 2. Following Brandi and Salaün (Eur. J. Org. Chem. 1999, 2725), the hemiketal 4 was carried onto the aldehyde 9. Condensation with nitromethane followed by dehydration gave the unsaturated nitrile oxide, which cyclized to 10. Epoxidation of 10 across the more open face gave an intermediate epoxide. Addition of 11 to the epoxide, promoted by InBr3, delivered 12 with good stereocontrol. CeCl3-mediated addition of 1-propynyl lithium completed the assembly of 1. A cyclopropanone could be seen as the addition product of carbon monoxide to an alkene. On exposure of 1 to acid, this formal addition was reversed, leading to the β-lactam 2. A computational study of this cleavage was recently reported (Eur. J. Org. Chem. 2011, 5608). Conceptually, one can imagine protonation activating the C–N bond for cleavage, leading to an intermediate such as 14, which then fragments to the acylium ion, leading to cyclization. It is unlikely that 14 would have any real lifetime. On warming with the Petasis reagent, the Boc-protected β-lactam was converted to the alkene 15. Hydroboration proceeded to give the alcohol 16 as a single diastereomer. Reduction followed by oxidation to 17 then set the stage for intramolecular aldol condensation to give 18. The last challenge was the diastereoselective assembly of the N-methoxyoxindole. To this end, oxidation and dehydration of 18 led to the bromo amide 20. As hoped, Heck reductive cyclization proceeded across the more open face of the alkene, leading to 21. Hydroxyl-directed hydrosilylation of the pendant alkyne to give the ethyl ketone then completed the synthesis of gelsemoxonine 3. Twice in this synthesis, advantage was taken of the preparation and reactivity of heteroatom-substituted alkenes. Dimethyl dioxirane, generated as a solution in acetone, was sufficiently water free that the epoxide derived from 10 could survive long enough to react in a bimolecular sense with the ketene silyl acetal 11.

ChemInform Abstract: Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Carbon Monoxide as the Reductant.

ChemInform ◽  
2016 ◽  
Vol 47 (3) ◽  
Author(s):  
Francesco Ferretti ◽  
Mohamed A. EL-Atawy ◽  
Stefania Muto ◽  
Mohamed Hagar ◽  
Emma Gallo ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Reductive Cyclization ◽  
Palladium Catalyzed

Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Carbon Monoxide as the Reductant

2015 ◽  
Vol 2015 (26) ◽  
pp. 5712-5715 ◽  
Author(s):  
Francesco Ferretti ◽  
Mohamed A. EL-Atawy ◽  
Stefania Muto ◽  
Mohamed Hagar ◽  
Emma Gallo ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Reductive Cyclization ◽  
Palladium Catalyzed

Carbon monoxide poisoning

2000 ◽  
Vol 12 (4) ◽  
pp. 354-357
Author(s):  
David R Smart ◽  
Paul D Mark
Keyword(s):  
Carbon Monoxide ◽  
Carbon Monoxide Poisoning
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