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Synlett 2003(12): 1871-1873  
DOI: 10.1055/s-2003-41468
LETTER
© Georg Thieme Verlag Stuttgart · New York

Use of (NHC)Pd(η3-allyl)Cl (NHC = N-Heterocyclic Carbene) in a Palladium-mediated Approach to Cryptocarya Alkaloids

Simon S. Cämmerer, Mihai S. Viciu, Edwin D. Stevens, Steven P. Nolan*
Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, USA
e-Mail: snolan@uno.edu;
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Publication History

Received 23 June 2003
Publication Date:
19 September 2003 (online)

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Abstract

The palladium-mediated intramolecular aryl amination of 7-benzyloxy-1-(2-bromo-4,5-dimethoxy-benzyl)-1,2,3,4-tetrahydro-6-methoxy-isoquinoline catalyzed by a recently discovered, air and moisture stable (NHC)Pd(η3-allyl)Cl (NHC = N-heterocyclic carbene) complex provides 2-benzyloxy-5,6,12,12a-tetrahydro-3,9,10-trime-thoxydibenz-[b,g]-indolizine in high yield. Effects of the solvent, the catalyst loading and the nature of the NHC-ancilliary ligand on the efficacy of the reaction were examined. Using identical conditions 7-benzyloxy-1-(2-chloro-4,5-methylendioxybenzyl)-1,2,3,4-tetrahydro-6-methoxyisoquinoline leads to 2-benzyloxy-5,6-12,12a-tetrahydro-3-methoxy-9,10-methylendioxydibenz-[b,g]-indolizine, also in high yield. Use of the catalytic intramolecular aryl amination step allows for the straightforward synthesis of the alkaloids rac-cryptaustoline and rac-cryptowoline.

Keywords

Pd-mediated aryl amination - N-heterocyclic carbene - dibenzopyrrocoline-alkaloids