- Highly Enantioselective, Organocatalytic, and Scalable Synthesis of a Rare cis,cis-Tricyclic Diterpenoid
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A highly enantioselective, organocatalytic, and scalable synthesis of a very unusual cis-decalin-cis-hydrindane tricyclic diterpenoid system has been achieved. Despite the prevalent pharmacological space that the related trans,trans and trans,cis-systems occupy, there have been no reports of an asymmetric synthesis of the cis,cis systems in the literature until now. We demonstrate the flexibility of our approach not only through access to a diverse range of products, all of which are attained in exceptionally high selectivities, but also by showing their easy conversion to the corresponding trans,cis-system and other derivatives.
- Townsend, Daniel,Shankland, Kenneth,Weymouth-Wilson, Alex,Komsta, Zofia,Evans, Tim,Cobb, Alexander J. A.
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supporting information
p. 3504 - 3508
(2020/03/05)
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- Synthesis of highly strained bicyclic[3.n.1]alkenes by a metal-catalyzed Conia-ene reaction
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A high yielding metal-catalysed Conia-ene reaction of 2-acetylenic ketones for the synthesis of bicyclo[3.n.1]alkenes has been developed. This simple and efficient 6-endo-dig-cyclization protocol enables the synthesis of a wide variety of bicyclic systems, present in many natural products.
- Kallepu, Shivakrishna,Gollapelli, Krishna Kumar,Nanubolu, Jagadeesh Babu,Chegondi, Rambabu
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supporting information
p. 16840 - 16843
(2015/11/27)
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- Direct amino acid-catalyzed cascade biomimetic reductive alkylations: Application to the asymmetric synthesis of Hajos-Parrish ketone analogues
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A direct amino acid-catalyzed chemo- and enantioselective process for the double cascade synthesis of highly substituted 2-alkyl-cyclopentane-1,3-diones, 2-alkyl-3-methoxy-cyclopent-2-enones and Hajos-Parrish (H-P) ketone analogs is presented via reductive alkylation chemistry. For the first time, we have developed a single-step alkylation of cyclopentane-1,3-dione with aldehydes/ketones and a Hantzsch ester through an organocatalytic reductive alkylation strategy. A direct combination of amino acid-catalyzed cascade olefination-hydrogenation and cascade Robinson annulations of cyclopentane-1,3-dione, aldehydes/ketones, a Hantzsch ester and methyl vinyl ketone furnished the highly functionalized H-P ketone analogues in good to high yields and with excellent enantioselectivities. Many of the reductive alkylation products have shown direct applications in pharmaceutical chemistry.
- Ramachary, Dhevalapally B.,Kishor, Mamillapalli
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supporting information; experimental part
p. 4176 - 4187
(2009/02/07)
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- Palladium-catalyzed synthesis of substituted cycloheptane-1,4-diones by an asymmetric ring-expanding allylation (AREA)
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(Chemical Equation Presented) The right AREA: Functionalized, seven-and eight-membered carbocycles are available from an asymmetric Pd-catalyzed decarboxylative fragmentation of strained bicyclo[3.2.0]heptane-2-ones (see scheme, dba = trans,trans-dibenzylidene-acetone). The products were formed in a sequence of [2+2] cycloaddition, retro-aldol reaction, and asymmetric allylation of ketone enolates.
- Schulz, Sabrina R.,Blechert, Siegfried
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p. 3966 - 3970
(2008/03/12)
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- Selective reduction of the acyl group in cyclic α-acyl-β-dicarbonyl compounds with sodium cyanoborohydride. Efficient synthesis of cyclic α-alkyl-β-dicarbonyl compounds
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Efficient synthesis of cyclic α-alkyl-β-dicarbonyl compounds of the cyclopentane, cyclohexane, tetronic acid, and α-pyrone series from the corresponding cyclic α-acyl-β-dicarbonyl compounds under the action of NaBH3(CN) in a THF-HCl system is described.
- Pashkovsky,Lokot',Lakhvich
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p. 324 - 326
(2007/10/03)
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- An efficient synthesis of alkyl substituted cyclic 1,3-diones
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An efficient method for the synthesis of cyclic α-alkyl β-dicarbonyl compounds of cyclopentane, cyclohexane, tetronic acid and α-pyrone series is described. The method consists of the selective transformation of the corresponding cyclic β,β′-tricarbonyl compounds by NaBH3CN in a mixture of THF and 2N aqueous HCl.
- Pashkovsky,Lokot,Lakhvich
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p. 1391 - 1394
(2007/10/03)
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- Substituent Effects on the CC Bond Strength, 16. - Thermal Stability and Enthalpies of Formation of β-Dicarbonyl Compounds. - Stabilisation Enthalpies of α,α'-Diketoalkyl Radicals
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The geminal interactions of the two carbonyl groups in seven β-diketones of the type 8-9 and 11-13 were estimated from their enthalpies of formation, which were deduced from their heats of combustion and enthalpies of vaporization.The radical stabilisation enthalpies RSE of the α,α'-diketoalkyl radicals 9-13 were obtained from the enthalpies of activation ΔH(excit.) of thermal CC bond cleavage of eight model compounds of the type 9-13 by their comparison with ΔH(excit.) of comparable hydrocarbons of similar strain.For non-cyclic α,α'-diacylalkyl radicals and six-membered cyclic ones RSE = 54.8 +/- 1.3 kJ mol-1 was determined, which indicates an additive stabilisation by two carbonyl groups. - Key Words: Enthalpies of formation/ Geminal substituents, energetic interaction of/ Bond cleavage, C-C, kinetics of/ Radicals, stability of/ Increments, thermochemical/ Bond strength, substituent effects on
- Noelke, Margot,Verevkin, Sergej P.,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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- AN IMPROVED PINACOL REARRANGEMENT FOR THE SYNTHESIS OF 2-ALKYL-1,3-CYCLOPENTADIONES
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2-Methyl, 2-ethyl and 2-isopropyl-1,3-cyclopentadiones are prepared by a modification of the method described by Nakamura, et al.
- Martinez, Rodolfo A.,Rao, Pemmaraju N.,Kim, Hyun K.
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p. 373 - 378
(2007/10/02)
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- Synthesis of 2-alkyl-cyclopentan-1,3-diones
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2-Lower alkyl-cyclopentan-1,3-diones are prepared in high yield by cyclization of gamma-ketoesters in the presence of a colloidal suspension of an alkali metal primary lower alcoholate.
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