- Primary Aminothiourea-Catalyzed Enantioselective Synthesis of Rauhut-Currier Adducts of 3-Arylcyclohexenone with a Tethered Enone on the Aryl Moiety at the Ortho -Position
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An enantioselective synthesis of Rauhut-Currier (RC) adducts from 3-aryl cyclohexenone with a tethered enone moiety at the ortho-position on the aryl group is accomplished. This method provides a wide range of valuable synthetic building blocks having a unique [6-5-6] all-carbon-fused tricyclic skeleton. A primary amine-containing thiourea, a bifunctional organocatalyst, was found to be an efficient catalyst for this transformation. The primary amine counterpart of the catalyst possibly activates the aliphatic enone via dienamine formation (HOMO activation), whereas the thiourea counterpart activates the tethered enone (LUMO activation). Considering the difficulty in achieving an RC reaction of β,β-disubstituted (alkyl and aryl) enones, this method would be significantly rewarding.
- Maity, Sanjay,Sar, Suman,Ghorai, Prasanta
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Read Online
- Four-Step One-Pot Catalytic Asymmetric Synthesis of Polysubstituted Tricyclic Compounds: Lipase-Catalyzed Dynamic Kinetic Resolution Followed by an Intramolecular Diels-Alder Reaction
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Starting from readily available tertiary alcohols, four different reactions (a 1,3-migration of a hydroxy group, kinetic resolution, racemization, and an intramolecular Diels-Alder reaction) took place under co-catalysis by lipase and oxovanadium compounds in a one-pot process to produce polysubstituted tricyclic carbon frameworks in high yields and with high enantioselectivities. The key to the success of this process was the discovery that a silyl group attached to the terminal carbon of the vinyl moiety completely controls the direction of hydroxy group migration.
- Tsuchimochi, Izuru,Hori, Shuhei,Takeuchi, Yasuo,Egi, Masahiro,Satoh, Tomo-O,Kanomata, Kyohei,Ikawa, Takashi,Akai, Shuji
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supporting information
p. 822 - 828
(2021/02/16)
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- Palladium-catalyzed asymmetric direct intermolecular allylation of α-aryl cyclic vinylogous esters: Divergent synthesis of (+)-oxomaritidine and (?)-mesembrine
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We demonstrate that α-aryl cyclic vinylogous esters are competent substrates in the direct intermolecular Pd-catalyzed asymmetric allylic alkylation, enabling a straightforward enantioselective synthesis of 6-allyl-6-aryl-3-ethoxycyclohex-2-en-1-ones, common motifs embedded in numerous structurally diverse natural products. As an initial demonstration of the utility of this protocol, the first catalytic enantioselective total synthesis of (+)-oxomaritidine and an improved five-step catalytic enantioselective synthesis of (?)-mesembrine have been completed divergently.
- Wang, Wei,Dai, Jun,Yang, Qiqiong,Deng, Yu-Hua,Peng, Fangzhi,Shao, Zhihui
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supporting information
p. 920 - 924
(2021/02/16)
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- Enantioselective Hydrogenation of Endocyclic Enones: the Solution to a Historical Problem?
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The enantioselective hydrogenation of endocyclic enones has been a historical problem for homogeneous catalysis. We herein report an efficient method to reduce endocyclic enones with molecular hydrogen. Catalyzed by a rhodium/Zhaophos complex, a variety of enones with five-, six- or seven-member ring were hydrogenated with high enantioselectivity (92%—99% ee). Excellent chemo- and enantioselectivity demonstrated this method was successfully applied in the enantioselective hydrogenation of citral to produce enantio-enriched citronellal.
- Lang, Qiwei,Yang, Huaxin,Gu, Guoxian,Feng, Qiang,Wen, Jialin,Zhang, Xumu
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supporting information
p. 933 - 936
(2021/03/03)
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- Rapid and Multigram Synthesis of Vinylogous Esters under Continuous Flow: An Access to Transetherification and Reverse Reaction of Vinylogous Esters
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An environmentally benign approach for the synthesis of vinylogous esters from 1,3-diketone and its reverse reaction under continuous-flow has been developed with alcohols in the presence of inexpensive Amberlyst-15 as a catalyst. This methodology is highly selective and general for a range of cyclic 1,3-dicarbonyl compounds which gives a library of linear alkylated and arylated vinylogous esters in good to excellent yield under solvent and metal free condition. Furthermore, the long-time experiment in a continuous-flow up to 40 h afforded 8.0 g of the vinylogous ester with turnover number (TON) = 28.6 and turnover frequency (TOF) = 0.715 h-1 using Amberlyst-15 as a catalyst. Furthermore, a continuous-flow sequential transetherification of vinylogous esters with various alcohols has been achieved in high yield. Reversibly, this vinylogous ester was deprotected or hydrolyzed into ketone using environmentally benign water as a solvent and Amberlyst-15 as a catalyst under continuous-flow process.
- Mohanta, Nirmala,Chaudhari, Moreshwar B.,Digrawal, Naveen Kumar,Gnanaprakasam, Boopathy
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p. 1034 - 1045
(2019/05/24)
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- DIHYDROPYRIMIDINE DERIVATIVES AND USES THEREOF IN THE TREATMENT OF HBV INFECTION OR OF HBV-INDUCED DISEASES
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Provided herein are dihydropyrimidine derivatives which are useful in the treatment of HBV infection or HBV-induced diseases, as well as pharmaceutical or medical applications thereof.
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Page/Page column 69-70
(2019/11/28)
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- Total Synthesis of (-)-Xylogranatopyridine B via a Palladium-Catalyzed Oxidative Stannylation of Enones
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We report a total synthesis of the pyridine-containing limonoid alkaloid (-)-xylogranatopyridine B in 11 steps from commercially available dihydrocarvone. The central pyridine ring was assembled by a late-stage fragment coupling approach employing a modified Liebeskind pyridine synthesis. One fragment was prepared by an allyl-palladium catalyzed oxidative enone β-stannylation, in which the key bimetallic β-stannyl palladium enolate intermediate undergoes a β-hydride elimination. This methodology also allowed introduction of alkyl and silyl groups to the β-position of enones.
- Schuppe, Alexander W.,Huang, David,Chen, Yifeng,Newhouse, Timothy R.
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supporting information
p. 2062 - 2066
(2018/02/19)
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- Synthesis of novel ent-kaurane-type diterpenoid derivatives effective for highly aggressive tumor cells
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We have designed and synthesized 6 ent-Kaurane-type diterpenoid derivatives containing α,β-unsaturated ketone moieties. In vitro, activity was evaluated against three human tumor cell lines and a rat myogenic cell line (HepG2, NSCLC-H292, SNU-1040, L6) by MTT assay. All the tested compounds exhibited comparable or higher activity than DDP and eriocalyxin B. Compounds 16, 17 and 18 are promising anti-tumor leads due to their cytotoxic potencies and higher selectivity, with SI values of 161.06, 47.80 and 128.20, respectively.
- Hu, Yu,Li, Xiao-Nian,Ma, Ze-Jin,Puno, Pema-Tenzin,Zhao, Yong,Zhao, Yan,Xiao, Ye-Zhi,Zhang, Wei,Liu, Jing-Ping
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- Synthesis of chiral seven-membered β-substituted lactams: Via Rh-catalyzed asymmetric hydrogenation
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Rh/bisphosphine-thiourea ligand (ZhaoPhos)-catalyzed asymmetric hydrogenation of seven-membered β-substituted α,β-unsaturated lactams was successfully developed to prepare various chiral seven-membered β-substituted lactams with good to excellent results (up to >99% conversion, 99% yield, and >99% ee).
- Huang, Yi,Li, Pan,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 8819 - 8823
(2018/11/30)
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- An Electrophilic Trifluoromethylthiolation of Silylenol Ethers and β-Naphthols with Diethylaminosulfur Trifluoride and (Trifluoromethyl)trimethylsilane
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An efficient and general trifluoromethylthiolation of silylenol ethers and β-naphthols have been accomplished employing the combination of diethylaminosulfur trifluoride (DAST) and (trifluoromethyl)trimethylsilane (CF3TMS) as source of electrophilic trifluoromethylthio moiety for the synthesis of α-trifluoromethylthiolated carbonyl compounds and β-naphthols in good yields. Important features of this method include wide functional group tolerance and use of readily available DAST/CF3TMS. Potential of the methodology was demonstrated via the synthesis of α-trifluoromethylthiolated (+)-4-cholesten-3-one and naphthoquinone. (Figure presented.).
- Saravanan, Perumal,Anbarasan, Pazhamalai
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supporting information
p. 2894 - 2899
(2018/08/17)
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- Iodine-Promoted Semmler–Wolff Reactions: Step-Economic Access to meta-Substituted Primary Anilines via Aromatization
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An atom- and step-economic access to an array of unprotected meta-substituted primary anilines was disclosed using the Semmler–Wolff reaction, promoted by molecular iodine. Therein, noble metal catalysts and inert atmosphere are unnecessary while the forcing reaction conditions and the lengthy synthesis can be avoided. The synthetic utility of this approach is evident in the de novo syntheses of three bioactive molecules with good total yields.
- Wang, Shi-Ke,You, Xia,Zhao, Da-Yuan,Mou, Neng-Jie,Luo, Qun-Li
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supporting information
p. 11757 - 11760
(2017/09/07)
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- Protecting-group-free synthesis of haterumadienone- and puupehenone-type marine natural products
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A divergent and expeditious access to haterumadienone- and puupehenone-type marine natural products has been achieved by using a newly developed hemiacetalization/dehydroxylation/hydroxylation/retro-hemiacetalization tandem reaction as one of the key steps. Its applicability is showcased by the first synthesis of haterumadienone, 20-hydroxyhaterumadienone, 20-epihydroxy-haterumadienone and 20-acetoxy-haterumadienone, as well as the facile synthesis of puupehenone, puupehedione and puupehenol. The synthesis is efficient, and atom- and step-economical (6 to 9 steps from commercially available starting materials), and requires no protecting groups and transition metals.
- Wang, Hong-Shuang,Li, Hui-Jing,Wang, Jun-Li,Wu, Yan-Chao
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supporting information
p. 2140 - 2144
(2017/07/24)
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- Synthesis method for marine natural product Puupehenone
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The invention relates to a synthesis method for a marine natural product Puupehenone, and belongs to the field of chemical synthesis. According to the synthesis method, (First) fragrant perillaldehyde and cyclohexanedione serve as initial raw materials; the synthesis method comprises the following steps: reacting the cyclohexanedione which is subjected to alkyl protection and the aldol of the (First) fragrant perillaldehyde to prepare beta-hydroxycyclohexanone of bicyclic sesquiterpanes; performing nucleophilic cyclization-elimination reaction of attacking a carbonyl by a hydroxyl under the catalysis of an acid to obtain a skeleton of the marine natural product Puupehenone; oxidizing the carbonyl at the ortho-position of an unsaturated ketene six-member ring carbonyl of the Puupehenone skeleton, and performing keto enol interconversion to obtain the final natural product Puupehenone. The synthesis method has the characteristics of few reaction steps, simple operation, high product selectivity, and application to industrial production and the like.
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Paragraph 0014
(2016/11/17)
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- Palladium-Catalyzed α-Arylation of Vinylogous Esters for the Synthesis of γ,γ-Disubstituted Cyclohexenones
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A palladium-catalyzed α-arylation of cyclic vinylogous esters to form products that are converted in one step to γ-alkyl-γ-aryl-substituted cyclohexenones is reported. This Pd-catalyzed reaction proceeds at room temperature, is generally high-yielding, and uses an amount of a commercially available catalyst as low as 0.25 mol %. The scope of aryl bromides is particularly broad, and alkenyl bromides can also be used. This two-step protocol, comprising α-arylation and reductive transposition, can be performed in one pot and is applicable to gram-scale synthesis.
- Johnson, Thomas,Pultar, Felix,Menke, Friedericke,Lautens, Mark
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supporting information
p. 6488 - 6491
(2016/12/23)
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- Highly enantioselective synthesis of chiral cyclic allylic amines via RH-catalyzed asymmetric hydrogenation
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Highly regioselective and enantioselective asymmetric hydrogenation of cyclic dienamides catalyzed by an Rh-DuanPhos complex has been developed, which provides a readily accessible method for the synthesis of chiral cyclic allylic amines in excellent enantioselectivities (up to 99% ee). The products are valuable chiral building blocks and could be easily transformed to multisubstituted cyclohexane derivatives.
- Zhou, Ming,Liu, Tang-Lin,Cao, Min,Xue, Zejian,Lv, Hui,Zhang, Xumu
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supporting information
p. 3484 - 3487
(2014/07/21)
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- Ionic liquid supported on magnetic nanoparticles as highly efficient and recyclable catalyst for the synthesis of β-keto enol ethers
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A magnetically ionic liquid supported on γ-Fe2O 3 nanocatalyst (AlxCly-IL-SiO 2γ-Fe2O3) was synthesized and evaluated as a recoverable catalyst for the synthesis of β-keto enol ethers. The immobilized catalyst proved to be effective and provided the products in high to excellent yield at room temperature. Moreover, the catalyst could be easily recovered by magnetic separation and recycled for six times without significant loss of its catalytic activity.
- Li, Pei-He,Li, Bao-Le,Hu, Hai-Chuan,Zhao, Xiao-Na,Zhang, Zhan-Hui
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p. 118 - 122
(2014/01/17)
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- Convenient synthesis of (e)-5-aryl(halo)methylenebicyclo-[2.2.2]oct-2-enes and -[2.2.1]hept-2-enes via Lewis acid-promoted carbohalogenation of cyclic 2,6-enynols
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An efficient synthesis of (E)-5-aryl(halo)-methylenebicyclo[2.2.2]oct-2-enes is reported. Lewis acid-promoted carbohalogenation of 4-(3-arylprop-2-ynyl)-cyclohex-2-enols in dichloromethane proceeds rapidly to afford the exo-methylenebridged bicycles in good yields. This method also provides an easy access to (E)-5-aryl(halo)methyl-ACHTUNGTRENUNGenebicyclo[2.2.1]hept-2-enes from the five-membered ring 2,6-enynols. The reactions are procedurally simple and high yielding, producing the aryl(halo) methylene-bridged bicycles in minutes under air and mild conditions.
- Yeh, Ming-Chang P.,Lin, Hsin-Hui,Kuo, Siou-Fu,Chen, Pei-Jie,Honga, Jyun-Wei
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supporting information
p. 3816 - 3820
(2015/01/16)
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- Diels-Alder reactions of masked o-benzoquinones with 1-vinylcyclohexenes: A short and efficient entry to highly functionalized decahydrophenanthrene skeleton
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Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding cycloaddition products, that is, decahydrophenanthrenes along with bicyclo[2.2.2]octenones. In the former case, the MOBs serve as the dienophile, and in the later case, the 1-vinylcyclohexenes act as the dienophile. The obtained bicyclo[2.2.2]octenones could be transformed into the corresponding decahydrophenanthrenes through a Cope rearrangement at 220 °C. Thus, these tandem reactions provide a short and efficient entry to the decahydrophenanthrene skeleton from easily available 2-methoxyphenols. Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding decahydrophenanthrenes and bicyclo[2.2.2]octenones. The obtained bicyclo[2.2.2]octenones could be transformed into decahydrophenanthrenes through a Cope rearrangement at 220 °C. Copyright
- Niu, Guang-Hao,Hou, Chieh-Shen,Chuang, Gary Jing,Wu, Chi-Phi,Liao, Chun-Chen
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supporting information
p. 3794 - 3801
(2014/06/24)
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- Simple, chemoselective, catalytic olefin isomerization
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Catalytic amounts of Co(SaltBu,tBu)Cl and organosilane irreversibly isomerize terminal alkenes by one position. The same catalysts effect cycloisomerization of dienes and retrocycloisomerization of strained rings. Strong Lewis bases like amines and imidazoles, and labile functionalities like epoxides, are tolerated.
- Crossley, Steven W. M.,Barabé, Francis,Shenvi, Ryan A.
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supporting information
p. 16788 - 16791
(2015/01/09)
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- Cyclization of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones
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The one-pot cyclization of 5-hexynoic acid to produce 3-alkoxy-2- cyclohexenones proceeds in good yields (58-90%). 3-Hexynoic acid was converted to its acyl chloride with the aid of oxalyl chloride and was cyclized to 3-chloro-2-cyclohexenone upon addition of indium(III) chloride. Subsequent addition of alcohol nucleophiles led to the desired 3-alkoxy-2-cyclohexenones.
- Hylden, Anne T.,Uzelac, Eric J.,Ostojic, Zeljko,Wu, Ting-Ting,Sacry, Keely L.,Sacry, Krista L.,Xi, Lin,Jones, T. Nicholas
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scheme or table
p. 1323 - 1326
(2011/11/06)
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- Design, synthesis, structure, and dehydrogenation reactivity of a water soluble o-iodoxybenzoic acid derivative bearing a trimethylammonium group
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5-Trimethylammonio-1, 3-dioxo-1, 3-dihydro-1λ5-benzo[d][1, 2]iodoxol-1-ol anion (AIBX 1a), an o-iodoxybenzoic acid (IBX) derivative having the trimethylammonium moiety on its phenyl ring, possesses very good solubility in water and distinct oxidative properties from IBX, which is demonstrated in the oxidation of various β-keto esters to the corresponding dehydrogenated products using water as cosolvent. The regeneration of AIBX 1a can be easily realized from the reaction mixture due to its good water solubility.2011 American Chemical Society.
- Cui, Li-Qian,Dong, Zhi-Lei,Liu, Kai,Zhang, Chi
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supporting information; experimental part
p. 6488 - 6491
(2012/02/02)
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- Formation of quaternary chiral centers by N-Heterocyclic carbene-CuCatalyzed asymmetric conjugate addition reactions with grignard reagents on trisubstituted cyclic enones
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The copper-catalyzed conjugate addition of Grignard reagents to 3-substituted cyclic enones allows the formation of all-carbon chiral quaternary centers. We demonstrate in this article that N-heterocyclic carbenes act as efficient chiral ligands for this transformation. High enantioselectivities (up to 96% ee) could be obtained for a variety of substrates.
- Kehrli, Stefan,Martin, David,Rix, Diane,Mauduit, Marc,Alexakis, Alexandre
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supporting information; experimental part
p. 9890 - 9904
(2010/11/04)
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- Iron(III) tosylate in the preparation of dimethyl and diethyl acetals from ketones and β-keto enol ethers from cyclic β-diketones
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An efficient method for conversion of ketones to their corresponding dimethyl and diethyl acetals and of cyclic β-diketones into β-keto enol ethers using Fe(OTs)3 as a catalyst is described. Copyright Taylor & Francis Group, LLC.
- Mansilla, Horacio,Afonso, Maria M.
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p. 2607 - 2618
(2008/12/22)
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- A flexible, stereoselective approach to the decorated cis-hydrindane skeleton: Synthesis of the proposed structure of faurinone
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A flexible, stereoselective approach to the cis-hydrindane motif found in a number of biologically active natural products that utilizes highly diastereoselective SmI2-mediated cyclizations of aldehyde and halide substrates was demonstrated. Aldehydes were prepared to investigate the stereoselectivity of the proposed SmI2-mediated construction of the cis-hydrindane system. Treatment of aldehydes with SmI2 in THF and tBuOH resulted in successful cyclization and construction of three contiguous stereocenters. This cyclization proceeds through reduction of the aldehyde and addition of the resulting ketyl-radical anion to the alkene through anti-transition structure to give samarium (III) enolates. It was observed that SmI2-mediated halide-alkene cyclizations provide an easy alternative for the synthesis of less oxygenated targets.
- Findley, Thomas J. K.,Sucunza, David,Miller, Laura C.,Davies, David T.,Procter, David J.
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supporting information; experimental part
p. 6862 - 6865
(2009/07/18)
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- New vistas in quinoline synthesis
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The gold-catalyzed Friedlander reaction was applied to the condensation of 2-aminoarylketones with β-keto-esters, β-diketones, β-keto-amides, and β-keto-sulfones to afford a diverse range of 2,3,4-trisubstituted quinolines in 3-82% yield. The seven-membered rings 1,3-cycloheptadione and azepane-2,4-dione reacted smoothly in 75% yield. An alternative procedure for the synthesis of 3-(methanesulfonyl)quinolines was developed and provided an entry into late stage manipulation of the 4-position of these quinolines. The requisite 2-aminoarylketones for the Friedlander reaction were prepared in one pot by modified Sugasawa reaction using gallium(III) chloride and boron(III) chloride in 12-54% yield.
- Atechian, Sarkis,Nock, Nadine,Norcross, Roger D.,Ratni, Hassen,Thomas, Andrew W.,Verron, Julien,Masciadri, Raffaello
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p. 2811 - 2823
(2007/10/03)
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- Unexpected regiospecific reactivity of a substituted phthalic anhydride
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Regioselective nucleophilic addition at C1 of anhydride 7 by a range of nucleophiles occurs to produce amide, ester and thioester derivatives 8-15 (60-99%). The increased electrophilic reactivity of the C1 carbonyl group of anhydride 7 is supported by a competition experiment with phthalic anhydride. Unexpected formation of lactams 18 and 19 from amides 12 and 13 was shown to proceed via the lactamols 16 and 17 and could be controlled by the reaction conditions. The solid-state structure of 19 is reported.
- Petersson, Maria J.,Marchal, Camille,Loughlin, Wendy A.,Jenkins, Ian D.,Healy, Peter C.,Almes?ker, Ann
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p. 1395 - 1401
(2007/10/03)
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- Ytterbium triflate catalyzed synthesis of β-keto enol ethers
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β-Keto enol ethers have been synthesized in very good yield in solvent-free conditions from differently substituted alcohols and β-diketones in the presence of Yb(OTf)3 as catalyst. The method is applicable to both cyclic and acyclic β-diketones with only slight differences in the experimental procedure.
- Curini, Massimo,Epifano, Francesco,Genovese, Salvatore
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p. 4697 - 4700
(2007/10/03)
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- An efficient conversion of β-diketones into β-keto enol ethers with P2O5/SiO2 under solvent-free conditions
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P2O5/SiO2 was found to be an efficient reagent for converting cyclic-β-diketones into their corresponding β-keto enol ethers at room temperature under solvent-free conditions.
- Cui, Zhen-Shui,Zhang, Zhan-Hui,Liu, Shu-Fen
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p. 390 - 392
(2007/10/03)
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- Cerium(IV) ammonium nitrate-catalyzed synthesis of β-keto enol ethers from cyclic β-diketones and their deprotection
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A mild and efficient method for etherification of cyclic β-diketones with alcohols has been developed using a catalytic amount of cerium(IV) ammonium nitrate at room temperature to afford the corresponding β-keto enol ethers in good to excellent yields. The deprotections of enol ethers in water-acetonitrile (1:1) using a catalytic amount (10 mol %) of cerium(IV) ammonium nitrate have also been achieved. Copyright
- Banerjee, Biplab,Mandal, Samir Kumar,Roy, Subhas Chandra
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- B(C6F5)3-catalyzed synthesis of β-keto enol ethers from β-diketones
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Efficient and practical synthesis of β-keto enol ethers from diketones catalyzed by B(C6F5)3 at room temperature has been described. Georg Thieme Verlag Stuttgart.
- Chandrasekhar,Srinivasa Rao,Ramakrishna Reddy
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p. 1471 - 1473
(2007/10/03)
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- Solvent free rapid synthesis of 3-alkoxycyclohex-2-en-1-one from 1,3-cyclohexanedione promoted by indium(in) chloride/silica gel
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A convenient and environmentally friendly method for the synthesis of 3-alkoxycyclohex-2-en-1-one 1 from cyclohexane-1,3-dioneonthe surface of silica gel impregnated with indium(III) chloride under microwave irradiation without any solvent has been reported CSIRO 2005.
- Murugan,Kamakshi,Reddy, Boreddy S. R.
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p. 228 - 230
(2008/02/04)
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- Microwave assisted rapid synthesis of 3-alkoxy-2-cyclohexen-1-ones from 1,3-cyclohexanedione
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Synthesis of 3-alkoxy-2-cyclohexen-1-ones from 1,3-cyclohexanedione with various alcohols has been achieved under microwave irradiation conditions within 7 min.
- Murugan,Reddy
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p. 1512 - 1514
(2007/10/03)
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- Iodine-catalyzed synthesis of β-keto enol ethers
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The use of iodine, as a catalyst for the synthesis of β-keto enol ethers at room temperature is reported. The use of iodine, as a catalyst for the synthesis of β-keto enol ethers at room temperature is reported.
- Bhosale, Rajesh S.,Bhosale, Sidhanath V.,Bhosale, Sheshanath V.,Wang, Tianyu,Zubaidha
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p. 7187 - 7188
(2007/10/03)
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- Niobium pentachloride activation of enone derivatives: Diels-Alder and conjugate addition products
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Niobium pentachloride has proven to be a powerful activating agent for Diels-Alder or conjugate addition reactions of cycloenones. The Diels-Alder product was obtained only with an unsubstituted enone (cyclohexenone) and the highly reactive diene cyclopentadiene; substituents in the β-position of enones seem to prevent Diels-Alder reaction: oxygenated substituents favor the formation of vinyl chlorides (ethyl ether or dichloromethane as solvents) or enol ethers (ethyl acetate as solvent), while a methyl substituent prevents (any kind of transformation with NbCl5. Less reactive dienes, furan and 2-methylfuran gave the conjugate addition products of the furan ring to the enone system.
- Gomes Constantino, Mauricio,Lacerda Jr., Valdemar,Da Silva, Gil Valdo José
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p. 456 - 464
(2007/10/03)
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- Chemo-enzymatic preparation of optically active endo- bicyclo[4.1.0]heptan-2-ols
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Resolutions of endo-bicyclo[4.1.O]heptan-2-ols were achieved by acylation in the presence of lipase from Candida antarctica (Novozym). The (1S,2R,6R) enantiomers reacted faster and the enantiomeric ratios were between 60 and 800 for the 6-substituted bicycloalkanols.
- Barnier, Jean-Pierre,Morisson, Veronique,Volle, Isabelle,Blanco, Luis
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p. 1107 - 1117
(2007/10/03)
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- Titanium(II)-based Z-reduction of alkynes. Syntheses of deuterium labelled linolenic and oleic acids and (3E,8Z,11Z)-tetradeca-3,8,11-trienyl acetate, the sex pheromone of a tomato pest, Scrobipalpuloides absoluta
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An operationally simple TiII-mediated, stereo- and regio-specific reduction of isolated, conjugated and methylene 'skipped' polyynes to the corresponding Z-polyenes in a one-pot procedure is described and applied inter alia to the syntheses of deuterium labelled linolenic and oleic acids. Final quenching with D2O (instead of H2O) results in regio- and stereo-specific Z-dideuteration of the alkyne. The synthesis of (3E,8Z,11Z)-tetradeca-3,8,11-trienyl acetate, the major sex pheromone of Scrobipalpuloides absoluta, a destructive pest of tomatoes, and the (3Z,8Z,11Z)-isomer, utilises this methodology in key reduction steps, and under- or over-reduction are negligible.
- Hungerford, Natasha L.,Kitching, William
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p. 1839 - 1858
(2007/10/03)
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- Temperature effect on [2+2] intramolecular photocycloadditions
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The temperature dependence of intramolecular [2+2] photocycloadditions has been studied for two series of cyclohexenones, α- and β-linked, respectively, to a variously substituted olefin moiety via a trimethylene chain. With one exception, the disappearance quantum yield of the starting material decreases sharply in a narrow temperature range to approximately one-half of its initial value. No such sharp temperature effect was observed on the product ratio, which either remains constant or varies monotonically over the entire temperature range. This indicates that the temperature effects on the disappearance rate and on the product distribution refer to two distinct processes. A mechanism rationalizing this behavior is proposed.
- Becker, Dan,Cohen-Arazi, Yael
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p. 8278 - 8284
(2007/10/03)
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- Photoreactions of Enones with Amines - Cyclization of Unsaturated Enones and Reductive Ring Opening by Photoinduced Electron Transfer (PET)
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Photolysis of the unsaturated enones 1 yields cycloaddition products 2 and 3 with varying regioselectivity.Under electron transfer conditions (PET) spirocyclic products 4 are formed.The straight cycloaddition products 2b, c, f are converted to the spirocyclic products 4b, c, f under the same reaction conditions.The cyclobutane 5 and cyclopropane 11 also undergo this new reductive ring opening reaction, while the stabilized system 7 is converted to reduced ring-enlarged triquinane 10 which may be interesting in natural product synthesis. - Irradiation of 2-cyclohexen-1-one (14) in the presence of N,N-dimethylallylamine (15) leads to the decahydroisoquinoline 18.A mechanism involving radical intermediates is discussed. Key Words: Photoinduced electron transfer / Cyclization / Ring opening / Enones
- Mattay, Jochen,Banning, Anja,Bischof, Eric W.,Heidbreder, Andreas,Runsink, Jan
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p. 2119 - 2128
(2007/10/02)
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- Pyrazolopyridine cycloalkanones and process for their preparation
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Novel tetrahydropyrazolo-[3,4-b]quinolinones, cyclopenta[b]pyrazolo-[4,3-e]pyridinones and cyclohepta[b]-pyrazolo[4,3-e]pyridinones, useful as anxiolytics having reduced side effects, are disclosed, including methods of preparation, pharmaceutical compositions containing them and intermediates used in their preparation.
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- New Synthetic Approaches to Fused-ring Carbocycles based on Intramolecular Photocycloadditions of 1,3-Dione Enol Esters
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Irradiation of 3-acetoxy-2-pent-4-enylcyclohex-2-enone (12) leads to the tricyclic adduct (18), in high yield (>95percent), which on hydrolytic cleavage in ethanolic potassium hydroxide gives rise to bicycloundecane-2,6-dione (20).In contrast, irradiation of the isomeric enol acetate, 3-acetoxy-4-pent-4-enylcyclohex-2-enone (17) led to the two photoadducts (25) and (26) resulting from intramolecular photocycloaddition, and to the trione (24) produced via photo-Fries rearrangement of (17); the formation of (25) and (26) followed from the structures (29) and (27) produced after saponification-retroaldolisation of mixtures containing (25) and (26).Irradiation of the 6-phenyl substituted enol ester (16) gave rise to only the photo-Fries rearrangement product (24).Irradiation of 1-acetoxy-2-pent-4-enylcyclopentene (39) led (93percent) to a 2:3 mixture of the photoadducts (41) and (42) whose structures followed from X-ray measurements.The corresponding cyclohexene (45), instead produced the product (46) of photo-Fries rearrangement on irradiation.Hydrolytic cleavage of (41) in KOH-EtOH leads to the bicyclodecanone (47), whereas similar treatment of (42) instead gave directly the aldol (49) by way of the transient retro-aldol intermediate (48).
- Begley, Michael J.,Mellor, Michael,Pattenden, Gerald
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p. 1905 - 1912
(2007/10/02)
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- The ?-? Interaction between Nitrile and Ethylene Functionalities
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The axial/equatorial free-energy difference for 3-cyano-1-methylenecyclohexane-2,2,4,4,6,6-d6 is 0.26 kcal/mol in CF2Cl2 and 0.07 kcal/mol in CHFCl2 at -102 deg C in favor of the equatorial conformer.The decreased equatorial preference in the polar, hydrogen-bonding solvent results from a less repulsive interaction between the 3-substituent and the 1-exo-methylene group.For the low-polarity solvent (CF2Cl2), the equatorial preference of cyano in the exo-methylene system is about the same as that in cyanocyclohexane (0.24 kcal/mol), which lacks the ?-? interactionin the axial conformation.These results contrast with polar, lone-pair-containing substituents such as methoxyl, which have dramatically increased equatorial preferences in the exo-methylene systems compared to their cyclohexyl counterparts.The ?-? interaction between the cyano group and the C=CH2 group appears to offer very little repulsion in comparison with the strong electrostatic interactions between methoxyl, hydroxyl, or thiomethyl and the same C=CH2 group.
- Lambert, Joseph B.,Taba, Kalulu M.
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p. 452 - 455
(2007/10/02)
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