- Complex polycyclic lactams from pericyclic cascade reactions of Zincke aldehydes
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(Chemical Equation Presented) In the course of a simple mechanistic study on the rearrangement of Zincke aldehydes to Z-α,β,γ,δ- unsaturated amides, a thermally induced pericyclic cascade rearrangement that converts Zincke aldehydes derived from allylic and homoallylic amines into polycyclic lactams was discovered. The key reaction involves an E-Z alkene isomerization, a 6? electrocyclic ring closure, a[1,5]-sigmatropic shift of hydrogen, a 6? electrocyclic ring-opening , and a Diels-Alder cycloaddition, and proceeds with excellent stereoselectivity. The unusual observation that furans and an indole serve as dienophiles in this cascade reaction permitted the synthesis of complex, functional group-rich tri- and tetracyclic lactams. In all cases, the rigid polycyclic products are available in only two steps from pyridinium salts and the allylic or homoallylic secondary amines.
- Steinhardt, Sarah E.,Vanderwal, Christopher D.
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supporting information; experimental part
p. 7546 - 7547
(2009/10/17)
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- Stereoselective synthesis of imidazolidin-2-ones via Pd-catalyzed alkene carboamination. Scope and limitations
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A method for the synthesis of imidazolidin-2-ones from N-allylureas and aryl or alkenyl bromides via Pd-catalyzed carboamination reactions is described. The N-allylurea precursors are prepared in one step from readily available allylic amines and isocyanates, and the Pd-catalyzed reactions effect the formation of a C-C bond, a C-N bond, and up to two stereocenters in a single step. Good diastereoselectivities are obtained for the conversion of substrates bearing allylic substituents to 4,5-disubstituted imidazolidin-2-ones, and excellent selectivity for the generation of products resulting from syn-addition across the alkene is observed when substrates derived from cyclic alkenes or E-1,2-disubstituted alkenes are employed. A brief discussion of reaction mechanism and product stereochemistry is presented.
- Fritz, Jonathan A.,Wolfe, John P.
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p. 6838 - 6852
(2008/09/21)
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- Synthesis of functionalised azecine and azonine derivatives via an enolate assisted aza Claisen rearrangement
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This paper describes the synthesis of functionalised azecine and azonine derivatives incorporating the adrenaline motif. In a key step, an enolate assisted aza Claisen rearrangement was employed to interconvert from 6- and 5-membered heterocycles to their corresponding 10- and 9-membered lactams.
- Bremner, John B.,Perkins, David F.
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p. 2659 - 2665
(2007/10/03)
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- The Synthesis of 1-Methyl-6,7,8,8a-tetrahydro-5H-indolizin-3-one by the Palladium-Catalyzed Cyclization of N-Bromoacetyl-2-vinylpiperidine
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N-Bromoacetyl-2-vinylpiperidine underwent cyclizalion to give indolizidine derivative in the presence of a base and a catalytic amount of palladium trifluoroacetate.
- Yang, Shyh-Chyun,Shea, Fang-Rong,Chung, Wen-Hung
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p. 293 - 296
(2007/10/03)
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- A metallocarbenoid approach to the formation of spirocyclic ammonium ylides leading to the preparation of medium-sized azacane rings
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A novel approach to azacyclooctene and azacyclononene containing substrates has been achieved via the intermediacy of a spirocyclic ammonium ylide derived from the diazodecomposition of a tethered α-diazoester moiety.
- Wright, Dennis L.,Weekly, R. Matt,Groff, Royce,McMills, Mark C.
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p. 2165 - 2168
(2007/10/03)
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- Thermally Induced Intramolecular Oxime Olefin Cycloadditions (IOOC) Leading to N-Bridgehead Systems. Stereochemistry and Molecular Mechanics Calculations
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The intramolecular oxime olefin cycloaddition (IOOC) of proline and pipecolinic acid derivatives proceeds thermally with a high degree of stereoselectivity to provide a new route to functionalized pyrrolizidines, indolizidines, or quinolizidines.The ring closure proceeds with simultaneous stereoselective introduction of three or four stereocenters.Molecular mechanics calculations have been refined to accurately predict not only which stereoisomer is preferred but also the syn and anti coupling constants in these tricyclic molecules.
- Hassner, Alfred,Maurya, Rakesh,Padwa, Albert,Bullock, William H.
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p. 2775 - 2781
(2007/10/02)
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- Electrophilic formamidines. Organometallic addition to 2-methoxy pyrrolidine or piperidine N-t-butyl formamidines. Formation of 2-substituted pyrrolidines and piperidines
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The title compounds were prepared by addition of Grignard reagents to methoxyformamidines 6 and 8 in ether at room temperature. Hydrolysis gives the free secondary amines, or in cases of volatile products, their thiourea derivatives.
- Gottlieb,Meyers
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p. 4723 - 4726
(2007/10/02)
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- New synthesis of heterocycles by use of palladium catalyzed cycli zation of α-haloamide with internal double bond
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α-Haloamide having internal double bond was allowed to react with a catalytic amount of Pd(PPh3)4 in the presence of base to produce a cyclized product in a fairly good yield possibly through the intermediate of -alkylmetal complex. By use of this method, five and six membered lactams, pyrrolizidine and quinolizidine derivatives were synthesized in fairly good yields.
- Mori, Miwako,Kanda, Nana,Oda, Izumi,Ban, Yoshio
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p. 5465 - 5474
(2007/10/02)
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