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Publikācija: Cyclization of Trichloroacetimidates via Olefin Aminopalladation beta-Heteroatom Elimination Route

Publication Type Publication (anonimusly reviewed) in a journal with an international editorial board indexed in other databases
Funding for basic activity Unknown
Defending: ,
Publication language English (en)
Title in original language Cyclization of Trichloroacetimidates via Olefin Aminopalladation beta-Heteroatom Elimination Route
Field of research 1. Natural sciences
Sub-field of research 1.4 Chemical sciences
Authors Ansis Maļeckis
Ieva Jaunzeme
Aigars Jirgensons
Keywords Amination / Palladium / Chirality / Heterocycles / Elimination
Abstract The cyclization of δ-acetoxy-O-allyl- and ε-acetoxy-O-homoallyl- trichloroacetimidates to 4-vinyloxazolines and a 4-vinyldihydrooxazine has been efficiently achieved by olefin aminopalladation– β-heteroatom elimination. (Z)-Allylic imidates bearing a secondary δ-acetoxy group underwent PdII-catalysed cyclization to give the E isomers of 4-vinyloxazolines selectively and gave no Overman rearrangement products. Introduction The transition-metal-catalysed formation, particularly with palladium, of the Csp3–N bond by amination of olefins has emerged as a powerful tool in organic synthesis. Distinguished methods are inter- and intramolecular PdII-catalysed oxidative amination using co-oxidants to regenerate the catalyst[1] as well as oxyamination[2] and deamination,[3] which are believed to proceed by a co-oxidant promoted Pd(II/IV) catalytic cycle. Other notable intramolecular reactions of this type are PdII-catalysed olefin hydroamination[4] terminated by the protolysis of the C–Pd bond and olefin haloamination[5] involving oxidative palladium–halide exchange in an alkylpalladium intermediate. An alternative way to regenerate the metal in the oxidation state required to maintain the catalytic cycle is β-heteroatom elimination from the alkylpalladium intermediate. A well-known example of this approach is the catalytic Overman rearrangement in which aminopalladation of the double bond is followed by elimination of the protonated β-imidate.[6] A few other related cyclization reactions of unsaturated carbamates by aminopalladation–deoxypalladation have also been reported.[ 7] Recently we have demonstrated that metal-catalysed Overman rearrangement of (E)-allylic imidates (E)-1 (R = Me, R1 = Me, TBS) bearing an oxy substituent at the δ position gives 4-vinyloxazolines 3 (R = Me) as byproducts [a] Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga 1006, Latvia Fax: +371-754-14-08 E-mail: aigars@osi.lv [b] Faculty of Materials Science and Applied Chemistry Department, Azenes 14, Riga 1048, Latvia Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejoc.200900917. Eur. J. Org. Chem. 2009, 6407–6412 © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 6407 Using a chiral substrate, it has been demonstrated that cyclization to 4-vinyloxazolines occurs with high chirality transfer. Stereoselective E isomer formation and chirality transfer provided a basis from which to discuss the possible reaction mechanism.
DOI: 10.1002/ejoc.200900917
Hyperlink: http://onlinelibrary.wiley.com/doi/10.1002/ejoc.200900917/pdf 
Reference Maļeckis, A., Jaunzeme, I., Jirgensons, A. Cyclization of Trichloroacetimidates via Olefin Aminopalladation beta-Heteroatom Elimination Route . European Journal of Organic Chemistry, 2009, Iss.36, pp.6407-6412. e-ISSN 1099-0690. Available from: doi:10.1002/ejoc.200900917
ID 6518