- Synthesis of β-Keto Lactone with Basic Skeleton of Przewalskin B
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The synthesis of β-keto lactone was completed using cyclohexanone as starting material. The α,β-unsaturated lactone was obtained through Reformatsky reaction and iodolactonization. The aforementioned lactone was converted into target compound 1 (β-keto lactone) by Nef oxidation and Claisen condensation in six steps with 17.9% overall yield.
- Liu, Jing-Ping,Wang, Li-Qin,Zhao, Yong,Zhao, Yan,He, Ying-Hui,Wang, Zi-Rong,Zhang, Hong-Bin
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- A concise total synthesis of (?)-γ-lycorane via an aromatic C[sbnd]H alkylation of unactivated secondary alkyl iodide
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A concise and straightforward total synthetic approach towards lycorine-type alkaloid (?)-γ-lycorane has been achieved in 7 steps. The key feature of the route is the employment of a palladium-catalyzed aromatic C[sbnd]H alkylation of unactivated secondary alkyl iodide. The synthetic protocols also involve a palladium-catalyzed deracemization of allylic carbonate, a Johnson-Claisen rearrangement and an iodocyclization.
- Huang, Shuangping,Ou, Wentao,Pang, Yiying,Wang, Xiaoji,Xiao, Hesheng,Zhang, Xuesong
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supporting information
(2020/03/04)
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- Radical-Mediated Strategies for the Functionalization of Alkenes with Diazo Compounds
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One of the most common reactions of diazo compounds with alkenes is cyclopropanation, which occurs through metal carbene or free carbene intermediates. Alternative functionalization of alkenes with diazo compounds is limited, and a methodology for the addition of the elements of Z-CHR2 (with Z = H or heteroatom, and CHR2 originates from N2 CR2) across a carbon-carbon double bond has not been reported. Here we report a novel reaction of diazo compounds utilizing a radical-mediated addition strategy to achieve difunctionalization of diverse alkenes. Diazo compounds are transformed to carbon radicals with a photocatalyst or an iron catalyst through PCET processes. The carbon radical selectively adds to diverse alkenes, delivering new carbon radical species, and then forms products through hydroalkylation by thiol-assisted hydrogen atom transfer (HAT), or forms azidoalkylation products through an iron catalytic cycle. These two processes are highly complementary, proceed under mild reaction conditions, and show high functional group tolerance. Furthermore, both transformations are successfully performed on a gram-scale, and diverse γ-amino esters, γ-amino alcohols, and complex spirolactams are easily prepared with commercially available reagents. Mechanistic studies reveal the plausible pathways that link the two processes and explain the unique advantages of each.
- Su, Yong-Liang,Liu, Geng-Xin,Liu, Jun-Wen,Tram, Linh,Qiu, Huang,Doyle, Michael P.
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supporting information
p. 13846 - 13855
(2020/09/21)
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- Method for synthesizing natural product gamma-lycorane
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The invention discloses a method for synthesizing a natural product gamma-lycorane. A classical Johnson-claisen rearrangement reaction, an I2 catalyzed N heterocyclic construction reaction, a palladium-catalyzed coupled ring closing reaction and the like
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Paragraph 0026; 0027
(2019/02/27)
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- Enantioselective Radical Construction of 5-Membered Cyclic Sulfonamides by Metalloradical C-H Amination
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Both arylsulfonyl and alkylsulfonyl azides can be effectively activated by the cobalt(II) complexes of D2-symmetric chiral amidoporphyrins for enantioselective radical 1,5-C-H amination to stereoselectively construct 5-membered cyclic sulfonami
- Hu, Yang,Lang, Kai,Li, Chaoqun,Gill, Joseph B.,Kim, Isaac,Lu, Hongjian,Fields, Kimberly B.,Marshall, McKenzie,Cheng, Qigan,Cui, Xin,Wojtas, Lukasz,Zhang, X. Peter
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supporting information
p. 18160 - 18169
(2019/11/19)
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- Rapid Access to Thiolactone Derivatives through Radical-Mediated Acyl Thiol-Ene and Acyl Thiol-Yne Cyclization
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A new synthetic approach to thiolactones that employs an efficient acyl thiol-ene (ATE) or acyl thiol-yne (ATY) cyclization to convert unsaturated thiocarboxylic acid derivatives into thiolactones under very mild conditions is described. The high overall yields, fast kinetics, high diastereoselectivity, excellent regiocontrol, and broad substrate scope of these reaction processes render this a very useful approach for diversity-oriented synthesis and drug discovery efforts. A detailed computational rationale is provided for the observed regiocontrol.
- McCourt, Ruairi O.,Dénès, Fabrice,Sanchez-Sanz, Goar,Scanlan, Eoin M.
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supporting information
p. 2948 - 2951
(2018/05/28)
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- Fungistatic activity of bicyclo[4.3.0]-γ-lactones
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Five optically active and sixteen racemic lactones (nine of them new) of bicyclo[4.3.0]nonane structure were synthesized. IC50 values for the following phytopathogens were determined: Aspergillus ochraceus AM 456, Fusarium culmorum AM 282, Fusarium oxysporum AM 13, Fusarium tricinctum AM 16. Effect of compound structures, especially stereogenic centers, on fungistatic activity has been discussed. The highest fungistatic activity was observed for trans-7,8-dibromo-cis-3-oxabicyclo[4.3.0]nonan-2-one (3c), IC50 = 30.1 μg/mL (0.10 μM/mL), and cis-7,8-epoxy-cis-3-oxabicyclo[4.3.0]nonan-2- one (3b), IC50 = 72.2 μg/mL (0.47 μM/mL), toward F. oxysporum AM 13.
- Olejniczak, Teresa,Boratynski, Filip,Bialonska, Agata
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p. 6071 - 6081
(2012/02/03)
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- Iron corroles and porphyrins as very efficient and highly selective catalysts for the reactions of α-diazo esters with amines
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Iron corroles and porphyrins catalyze the reactions of amines with ethyl diazoacetate extremely efficiently, leading to complete and rapid conversion into N-substituted glycine ethyl esters by simultaneous addition of the substrates to the catalysts. The selectivity toward activation of the NH bonds is remarkable and quite different from other catalysts. Georg Thieme Verlag Stuttgart.
- Aviv, Iris,Gross, Zeev
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p. 951 - 953
(2007/10/03)
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- 4-SUBSTITUTED IMIDAZOLE-2-THIONES AND IMIDAZOL- 2-ONES AS AGONISTS OF THE ALPHA- 2B AND ALPHA-2C ADRENERGIC RECEPTORS
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Compounds of Formula (I): where X is S and the variables have the meaning defined in the specification are specific or selective to alpha2B and/or alpha2C adrenergic receptors in preference over alpha2A adrenergic receptors, and as such have no or only minimal cardivascular and/or sedatory activity. These compounds of Formula (I) are useful as medicaments in mammals, including humans, for treatment of diseases and or alleviations of conditions which are responsive to treatment by agonists of alpha2B adrenergic receptors. Compounds of Formula (I) where X is O also have the advantageous property that they have no or only minimal cardivascular and/or sedatory activity and are useful for treating pain and other conditions with no or only minimal cardivascular and/or sedatory activity.
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- Inversion of the direction of stereoinduction in the coupling of chiral γ,δ-unsaturated fischer carbene complexes with o-ethynylbenzaldehyde
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(matrix presented) A variety of γ,δ-unsaturated carbene complexes that feature a stereogenic center at the β-carbon couple with 2-ethynylbenzaldehyde to afford hydrophenanthrene derivatives with a high degree of stereoinduction. The direction of stereoinduction is opposite for examples where the stereogenic center is acyclic vs examples where it is within a ring.
- Ghorai, Binay K.,Menon, Suneetha,Lee Johnson, Dennis,Herndon, James W.
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p. 2121 - 2124
(2007/10/03)
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- Intermolecular cyclopropanation versus CH insertion in Rh(II)-catalyzed carbenoid reactions
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The product ratio of intermolecular insertion and cyclopropanation in transition metal-catalyzed diazo decompositions depends strongly upon the metal, its ligands and upon the substituents of the diazo compound. Ethyl diazoacetate (2a) reacts with cyclohexene (1) almost exclusively by cyclopropanation. However, diazomalonate (2d) and methyl 2-diazophenylacetate (2e) in the presence of Rh(II) catalysts exhibit a marked tendency towards allylic CH insertion. With 1,4-cyclohexadiene (6), methyl 2- diazophenylacetate (2e) in the presence of chiral Rh(II) catalysts affords the allylic insertion product 7 in almost quantitative yield and with up to 74% ee. (C) 2000 Elsevier Science Ltd.
- Müller, Paul,Tohill, Sarah
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p. 1725 - 1731
(2007/10/03)
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- Ketone-directed peracid epoxidation of cyclic alkenes
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Ketone carbonyl groups are shown to direct the peracid epoxidation of cyclic alkenes with greater selectivity than that displayed by esters. An 18O labelling study is used to show that a dioxirane intermediate is not involved in these reactions.
- Armstrong, Alan,Barsanti, Paul A.,Clarke, Paul A.,Wood, Anthony
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p. 1373 - 1380
(2007/10/03)
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- Ketone-directed peracid epoxidation
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Ketone carbonyl groups are shown to direct the epoxidation of cyclic alkenes with higher selectivity than that displayed by esters. An 18O labelling study is used to show that a dioxirane intermediate is not involved in these reactions.
- Armstrong,Armstrong, Alan,Barsanti,Barsanti, Paul A.,Clarke,Clarke, Paul A.,Wood,Wood, Anthony
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p. 6155 - 6158
(2007/10/02)
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- The claisen rearrangement in synthesis: Acceleration of the johnson orthoester protocol en route to bicyclic lactones
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Catalysis of the Claisen orthoester rearrangement of triethyl orthoacetate and a number of 2-cycloalken-1-ols has been achieved using acidic catalysis and brief microwave thermolysis in DMF. Unlike conventional methods of thermolysis, very high yields of rearranged products are typically obtained in less than ten minutes, and the Claisen products themselves require no further purification. The synthetic utility of the products so obtained is demonstrated in a general synthesis of functionalized bicyclic lactones.
- Jones, Graham B.,Huber, Robert S.,Chau, Sotheary
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p. 369 - 380
(2007/10/02)
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- Lithium Perchlorate-Assisted Substitution Reactions of A11llylic Acetates and Allylic Alcohols
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Substitution reactions of allylic acetates and allylic alcohols by a variety of nucleophiles proceed smoothly in the presence of lithium perchlorate in ether, providing a convenient alternative to transition metal catalyzed methods.
- Pearson, William H.,Schkeryantz, Jeffrey M.
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p. 2986 - 2987
(2007/10/02)
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- Phosphonate Analogues of Chorismic Acid: Synthesis and Evaluation as Mechanism-Based Inactivators of Chorismate Mutase
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The mechanism of chorismate mutase, the enzyme which catalyzes the Claisen arrangement of chorismic to prephenic acid, remains a fascinating area for bioorganic research.This paper describes the enantioselective synthesis of phosphonochorismic acids 3 and
- Wood, Harold B.,Buser, Hans-Peter,Ganem, Bruce
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p. 178 - 184
(2007/10/02)
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- Use of Radical Ring-Opening for Introduction of Alkyl and Substituted Alkyl Groups with Stereochemical Control: A Synthetic Application of Cyclopropylcarbinyl Radicals
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Cyclopropylcarbinols 2a and 2b (see Scheme I), which are accessible by a number of routes, can be converted into the corresponding radicals 3a and 3b, respectively.These radicals undergo peripheral ring-opening of the cyclopropyl substructure to afford su
- Clive, Derrick L. J.,Daigneault, Sylvain
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p. 3801 - 3814
(2007/10/02)
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- Synthetic Applications of Radical Ring-Opening: Use of Cyclopropylmethyl Radicals
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Cycloropanation of cyclic allylic alcohols followed by radical deoxygenation leads, by peripheral ring-opening of the cyclopropylmethyl system, to alkyl-substituted cycloalkenes (Scheme 1); the alkyl group can itself be substituted (during the cyclopropan
- Clive, Derrick L. J.,Daigneault, Sylvain
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p. 332 - 335
(2007/10/02)
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- RHODIUM(II)2,4,6-TRIARYLBENZOATES: IMPROVED CATALYSTS FOR THE SYN CYCLOPROPANATION OF Z-OLEFINS
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The stereochemical course of the cyclopropanation of Z-olefins by ethyl diazoacetate in the presence of various binuclear rhodium(II)carboxylates was studied.The highest syn/anti ratio (up to 3) was obtained using Rh2(O2CR)3(O2CR') where R = 2,4,6-triarylphenyl and R' = CH3 or CF3.
- Callot, H. J.,Metz, F.
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p. 4495 - 4502
(2007/10/02)
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- STERICALLY CROWDED CYCLOPROPANATION CATALYSTS. SYN-SELECTIVITY USING RHODIUM(III)PORPHYRINS
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Rhodium(III)porphyrins catalyze the decomposition of ethyl diazoacetate and the transfer of ethoxycarbonylcarbene to alkenes to form cyclopropanes in moderate to high yields.When compared with other catalysts a large syn-selectivity was observed on reaction with cis-alkenes.This selectivity increased with the size of the substituents, and suggested a preferencial direction of approach of the alkene towards a rhodium-carbene complex.
- Callot, H. J.,Metz, F.,Piechocki, C.
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p. 2365 - 2369
(2007/10/02)
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