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Hydrogen-bond-directed highly stereoselective synthesis of Z-enamides via Pd-catalyzed oxidative amidation of conjugated olefins.
J Am Chem Soc. 2006 Oct 04; 128(39):12954-62.JA

Abstract

An efficient procedure for the preparation of Z-enamides has been developed, involving the reaction of primary amides with conjugated olefins using a Pd/Cu cocatalyst system. It was found that certain additives, such as phosphine oxides and phosphonates, increase the efficiency of the reaction in nonpolar solvents under an oxygen atmosphere, thus producing a variety of Z-enamides in high yields with excellent stereoselectivity under Wacker-type conditions. The oxidative amidation reaction has a broad substrate scope, allowing alkyl, aryl, and vinyl amides to react with olefins conjugated with ester, amide, phosphonate, and ketone groups. The notable preference for the formation of Z-enamides is presumably due to the presence of an intramolecular hydrogen bond between the amido proton and the carbonyl oxygen. The energy difference between two plausible sigma-alkylamidopalladium intermediates, leading to Z- and E-isomeric enamide products, respectively, was calculated to be 4.18 kcal/mol. The beta-hydride elimination step is assumed to be a stereochemistry-determining step in the overall oxidative amidation process, with the energy level for the transition state leading to the Z-enamide being 5.35 kcal/mol lower than that leading to the E-isomer. The efficiency of photoisomerization between Z- and E-enamides was observed to be largely dependent on the substrates' substituents, and certain E-enamides could be obtained in synthetically useful yields by photoirradiation of Z-isomers. Synthetic application of the present method was successfully demonstrated by a direct formal synthesis of cis-CJ-15,801.

Authors+Show Affiliations

Lee JM
Center for Molecular Design and Synthesis, Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea.
Ahn DS
No affiliation info available
Jung DY
No affiliation info available
Lee J
No affiliation info available
Do Y
No affiliation info available
Kim SK
No affiliation info available
Chang S
No affiliation info available

MeSH

AlkenesAmidesCatalysisHydrogen BondingModels, MolecularOxidation-ReductionPalladiumStereoisomerism

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17002392

Citation

Lee, Ji Min, et al. "Hydrogen-bond-directed Highly Stereoselective Synthesis of Z-enamides Via Pd-catalyzed Oxidative Amidation of Conjugated Olefins." Journal of the American Chemical Society, vol. 128, no. 39, 2006, pp. 12954-62.
Lee JM, Ahn DS, Jung DY, et al. Hydrogen-bond-directed highly stereoselective synthesis of Z-enamides via Pd-catalyzed oxidative amidation of conjugated olefins. J Am Chem Soc. 2006;128(39):12954-62.
Lee, J. M., Ahn, D. S., Jung, D. Y., Lee, J., Do, Y., Kim, S. K., & Chang, S. (2006). Hydrogen-bond-directed highly stereoselective synthesis of Z-enamides via Pd-catalyzed oxidative amidation of conjugated olefins. Journal of the American Chemical Society, 128(39), 12954-62.
Lee JM, et al. Hydrogen-bond-directed Highly Stereoselective Synthesis of Z-enamides Via Pd-catalyzed Oxidative Amidation of Conjugated Olefins. J Am Chem Soc. 2006 Oct 4;128(39):12954-62. PubMed PMID: 17002392.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Hydrogen-bond-directed highly stereoselective synthesis of Z-enamides via Pd-catalyzed oxidative amidation of conjugated olefins. AU - Lee,Ji Min, AU - Ahn,Doo-Sik, AU - Jung,Doo Young, AU - Lee,Junseung, AU - Do,Youngkyu, AU - Kim,Sang Kyu, AU - Chang,Sukbok, PY - 2006/9/28/pubmed PY - 2007/8/8/medline PY - 2006/9/28/entrez SP - 12954 EP - 62 JF - Journal of the American Chemical Society JO - J Am Chem Soc VL - 128 IS - 39 N2 - An efficient procedure for the preparation of Z-enamides has been developed, involving the reaction of primary amides with conjugated olefins using a Pd/Cu cocatalyst system. It was found that certain additives, such as phosphine oxides and phosphonates, increase the efficiency of the reaction in nonpolar solvents under an oxygen atmosphere, thus producing a variety of Z-enamides in high yields with excellent stereoselectivity under Wacker-type conditions. The oxidative amidation reaction has a broad substrate scope, allowing alkyl, aryl, and vinyl amides to react with olefins conjugated with ester, amide, phosphonate, and ketone groups. The notable preference for the formation of Z-enamides is presumably due to the presence of an intramolecular hydrogen bond between the amido proton and the carbonyl oxygen. The energy difference between two plausible sigma-alkylamidopalladium intermediates, leading to Z- and E-isomeric enamide products, respectively, was calculated to be 4.18 kcal/mol. The beta-hydride elimination step is assumed to be a stereochemistry-determining step in the overall oxidative amidation process, with the energy level for the transition state leading to the Z-enamide being 5.35 kcal/mol lower than that leading to the E-isomer. The efficiency of photoisomerization between Z- and E-enamides was observed to be largely dependent on the substrates' substituents, and certain E-enamides could be obtained in synthetically useful yields by photoirradiation of Z-isomers. Synthetic application of the present method was successfully demonstrated by a direct formal synthesis of cis-CJ-15,801. SN - 0002-7863 UR - https://www.unboundmedicine.com/medline/citation/17002392/Hydrogen_bond_directed_highly_stereoselective_synthesis_of_Z_enamides_via_Pd_catalyzed_oxidative_amidation_of_conjugated_olefins_ L2 - https://doi.org/10.1021/ja0639315 DB - PRIME DP - Unbound Medicine ER -