Dithiane anions undergo intramolecular conjugate additions with alpha,beta-unsaturated nitriles when a dithiane anion is tethered to N-1 of the 3-cyano-1,4,5,6-tetrahydropyridine nucleus. 3-Cyano-1-[2-(1,3-dithianyl-2-yl)ethyl]-1,4,5,6-tetrahydropyridine (1a) and the one-carbon homologue 1b cyclize in the presence of 12-crown-4 to generate indolizidine 3 and quinolizidine 9, in which the nitrile group exhibits a strong, thermodynamic preference for the axial orientation. Oxidation of Ib provides dithiane S-oxide 10 that undergoes a highly stereoselective conjugate addition to provide crystalline quinolizidine 13. The X-ray structure of 13 is reported and corroborates our ''peg-in-a-pocket'' principle for stereoselective conjugate additions with alpha,beta-unsaturated nitriles.
The development of catalysts based on earth abundant metals in place of noble metals is becoming a central topic of catalysis. We herein report a cobalt/tetraphosphine complex catalyzed homogeneous hydrogenation of polar unsaturated compounds using an air- and moisture-stable and scalable precatalyst. By activation with potassium hydroxide, this cobalt system shows both high efficiency (up to 24000
regioselective enamine exchange with N-methylhydrazine and 1,4,5,6-tetrahydro-pyridine-3-carbonitrile (8), followed by a subsequently occurring intramolecular cyclization and aromatization, starting from a cheap 3-cyanopyridine (7).
[4 + 2]-Cycloaddition Reactions between β-Acceptor-Substituted Enamines and 2-Vinylindole Radical Cations Acting as Hetero-Dienes
作者:Christoph F. Gürtler、Eberhard Steckhan、Siegfried Blechert
DOI:10.1021/jo951551o
日期:1996.1.1
[4 + 2]-Cycloadditionreactions between 2-vinylindoles acting as hetero-dienes and beta-acceptor substituted cyclic and acyclic enamines can be induced by formation of 2-vinylindole radical cations either via anodic oxidation or photoelectron transfer (PET) using catalytic amounts of triarylpyrylium tetrafluoroborates as sensitizers. In this way, pyrido[1,2-a]indoles or indolo[1,2-a]hexahydro-1,8-naphthyridines
Reactivity of 2-cyano-1,4,5,6-tetrahydro-1-pyridinecarboxylic acid esters towards various nucleophiles: Regio- and stereoselectivity of the attack
作者:P. Stanetty、M. D. Mihovilovic、K. Mereiter
DOI:10.1007/bf00806971
日期:1997.10
The synthesis and reactivity of the title compounds towards nucleophiles are discussed. The regio-and diastereoselectivity of the attack is highly dependent on the carbamic ester and the type of nucleophile applied. Both Michael type addition across the activated double bond and S(N)2T reaction at the carbamate carbon atom were observed. Structure assignment of the adducts in solution and in the solid state was performed utilizing high temperature NMR techniques as well as single crystal X-ray diffraction.
作者:Z. Hussain、F. F. Fleming、R. E. Norman、S. C. Chang
DOI:10.1107/s010827019501345x
日期:1996.4.15
The title nitrile 1-[4-(1,3-dithian-2-yl)butyl]-1,4,5,6-tetrahydropyridine-3-carbonitrile, C14H22N2S2} was prepared as part of our investigations into the conjugate addition reactions of unsaturated nitriles [Fleming & Pak (1995). J. Org. Chem. 60, 4299-4301]. The tetrahydropyridine ring adopts a half-chair conformation and is appended by a four-carbon chain to the dithiane ring which adopts a chair conformation.