Synthesis 2006(21): 3661-3669  
DOI: 10.1055/s-2006-950286
© Georg Thieme Verlag Stuttgart · New York

Coupling of β-Cyanocarbene-Chromium Complexes with 2-Alkynylbenzoyl Derivatives: A [5+5]-Cycloaddition Approach to Phenanthridines

Binay K. Ghorai, Shaofeng Duan, Delu Jiang, James W. Herndon*
Department of Chemistry and Biochemistry, New Mexico State University, MSC 3C, Las Cruces, NM 88003, USA
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Further Information

Publication History

Received 9 June 2006
Publication Date:
09 October 2006 (online)


The coupling of β-cyanocarbene complexes and 2-alkynylbenzoyl derivatives has been examined. The reaction afforded phenanthridine derivatives in a complex tandem process involving carbene-alkyne coupling, isobenzofuran formation, intramolecular Diels-Alder reaction using a nitrile dienophile, and deoxygenation. The chemistry could not be reproduced in non-chromium-based systems.


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  • 2b For the first example, see: Jiang D. Herndon JW. Org. Lett.  2000,  2:  1267 
  • Most examples involve electron-deficient nitriles; recent examples include:
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  • 25This compound is known; however, the spectral data are inaccessible: (Laboratorios Made S.A., Spain) Span. Patent 74-423501;
  • 25
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This compound was prepared from o-tolunitrile in a three-step sequence involving: (1) deprotonation with LDA followed by allylation with allyl bromide, (2) oxidation of the alkene to the aldehyde using OsO4/NaIO4, and (3) reaction of the aldehyde with 2-(dimethoxymethyl)phen-yllithium.


This is a variant of a literature procedure in reference 9b. This procedure is very reliable if one is careful to cut the potassium into small pieces and if the tetramethyl-ammonium acylate salt is prepared prior to the alkylation step. Otherwise we noted wide variances in the yields between different experimental runs.


Prepared from cis-1,2-cyclohexanedicarboxylic anhydride via amide formation (treatment with aqueous ammonia), followed by amide dehydration (Ac2O), followed by acid chloride formation (oxalyl chloride).


Prepared from reaction of the acid chloride (ref. 21) with aqueous dimethylamine.


This compound was prepared from Sonogashira coupling of hex-1-yne and N,N-dimethyl-2-iodobenzamide according to a literature procedure. See reference 15.