- Stereoselective reductions of N-Boc-hexahydro-1H-indolin-5(6H)-ones
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We report the divergent effects of a 3a-methyl and 3a-phenyl substituent on the chemoselectivity and stereoselectivity of reduction of the enamide moiety of N-Boc-hexahydro-1H-indolin-5(6H)-ones. Under ionic reduction conditions (triethylsilane/trifluoroacetic acid) the enamide group of 3a-methyl-N-Boc-hexahydro-1H-indolin-5(6H)-one was reduced to afford exclusively a cis ring-fused product. For the 3a-phenyl substituted analogue more forcing conditions (sodium cyanoborohydride at pH 2-2.5) were required and resulted in the selective reduction of the enamide group to give a trans ring-fused product as well as reduction of the ketone group.
- Brodney, Michael A.,Cole, Marcus L.,Freemont, Jamie A.,Kyi, Stella,Junk, Peter C.,Padwa, Albert,Riches, Andrew G.,Ryan, John H.
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- Complementary Photocatalytic Toolbox: Control of Intramolecular endo-versus exo-trig Cyclizations of α-Phenyl Olefins to Oxaheterocyclic Products
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The regioselectivity of the intramolecular cyclization of bifunctional α-phenyl alkenes can be controlled simply by the choice of the organic chromophore as the photocatalyst. The central photoredox catalytic reaction in both cases is a nucleophilic addition of the hydroxyl function to the olefin function of the substrates. N,N-(4-Diisobutylaminophenyl) phenothiazine catalyzes exo-trig cyclizations, whereas 1,7-dicyanoperylene-3,4,9,10-tetracarboxylic acid bisimides catalyze endo-trig additions to products with anti-Markovnikov regioselectivity. We preliminarily report the photoredox catalytic conversions of 11 representative substrates into 20 oxaheterocycles in order to demonstrate the similarity, but also the complementarity, of these two variants in this photoredox catalytic toolbox.
- Belov, Arina,Steuernagel, Desirée,Wagenknecht, Hans-Achim,Weick, Fabian
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supporting information
(2022/03/03)
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- A Mechanistically Inspired Halenium Ion Initiated Spiroketalization: Entry to Mono- and Dibromospiroketals
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Employing halenium affinity (HalA) as a guiding tool, the weak nucleophilic character of alkyl ketones was modulated by the templating effect of a tethered 2-tetrahydropyranyl(THP)-protected alcohol towards realizing a bromenium ion initiated spiroketaliz
- Ashtekar, Kumar Dilip,Borhan, Babak,Chakraborty, Ankush,Ding, Xinliang,Gholami, Hadi,Kiiskila, Lindsey,Moemeni, Mehdi,Rahn, Christopher,Toma, Edmond
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supporting information
(2022/01/13)
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- Strong acid-catalyzed electrophilic ring expansion of oxetanes and sulfoxonium ylides
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A strong protic acid-catalyzed electrophilic ring expansion of oxetanes into trans-2,3-disubstituted tetrahydrofuran derivatives using sulfoxonium ylides has been developed. This reaction produces functionalized trans-2,3-disubstituted tetrahydrofuran derivatives stereospecifically by using safe and stable sulfoxonium ylides without metal catalysts and the protection of inert gas.
- Xie, Wenlai,Xu, Jiaxi,Yuan, Wenhao
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- Catalytic Asymmetric Allylic Substitution with Copper(I) Homoenolates Generated from Cyclopropanols
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By using copper(I) homoenolates as nucleophiles, which are generated through the ring-opening of 1-substituted cyclopropane-1-ols, a catalytic asymmetric allylic substitution with allyl phosphates is achieved in high to excellent yields with high enantioselectivity. Both 1-substituted cyclopropane-1-ols and allylic phosphates enjoy broad substrate scopes. Remarkably, various functional groups, such as ether, ester, tosylate, imide, alcohol, nitro, and carbamate are well tolerated. Moreover, the present method is nicely extended to the asymmetric construction of quaternary carbon centers. Some control experiments argue against a radical-based reaction mechanism and a catalytic cycle based on a two-electron process is proposed. Finally, the synthetic utilities of the product are showcased by means of the transformations of the terminal olefin group and the ketone group.
- Shi, Chang-Yun,Yin, Liang,Zhang, Qi,Zhou, Si-Wei
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supporting information
p. 26351 - 26356
(2021/11/09)
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- Biocatalytic reduction of α,β-unsaturated carboxylic acids to allylic alcohols
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We have developed robust in vivo and in vitro biocatalytic systems that enable reduction of α,β-unsaturated carboxylic acids to allylic alcohols and their saturated analogues. These compounds are prevalent scaffolds in many industrial chemicals and pharmaceuticals. A substrate profiling study of a carboxylic acid reductase (CAR) investigating unexplored substrate space, such as benzo-fused (hetero)aromatic carboxylic acids and α,β-unsaturated carboxylic acids, revealed broad substrate tolerance and provided information on the reactivity patterns of these substrates. E. coli cells expressing a heterologous CAR were employed as a multi-step hydrogenation catalyst to convert a variety of α,β-unsaturated carboxylic acids to the corresponding saturated primary alcohols, affording up to >99percent conversion. This was supported by the broad substrate scope of E. coli endogenous alcohol dehydrogenase (ADH), as well as the unexpected CC bond reducing activity of E. coli cells. In addition, a broad range of benzofused (hetero)aromatic carboxylic acids were converted to the corresponding primary alcohols by the recombinant E. coli cells. An alternative one-pot in vitro two-enzyme system, consisting of CAR and glucose dehydrogenase (GDH), demonstrates promiscuous carbonyl reductase activity of GDH towards a wide range of unsaturated aldehydes. Hence, coupling CAR with a GDH-driven NADP(H) recycling system provides access to a variety of (hetero)aromatic primary alcohols and allylic alcohols from the parent carboxylates, in up to >99percent conversion. To demonstrate the applicability of these systems in preparative synthesis, we performed 100 mg scale biotransformations for the preparation of indole-3-aldehyde and 3-(naphthalen-1-yl)propan-1-ol using the whole-cell system, and cinnamyl alcohol using the in vitro system, affording up to 85percent isolated yield.
- Aleku, Godwin A.,Leys, David,Roberts, George W.
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p. 3927 - 3939
(2020/07/09)
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- Catalytic Regioselective Isomerization of 2,2-Disubstituted Oxetanes to Homoallylic Alcohols
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The selective isomerization of strained heterocyclic compounds is an important tool in organic synthesis. An unprecedented regioselective isomerization of 2,2-disubstituted oxetanes into homoallylic alcohols is described. The use of tris(pentafluorophenyl
- Cabré, Albert,Lledós, Agustí,Rafael, Sergi,Riera, Antoni,Sciortino, Giuseppe,Ujaque, Gregori,Verdaguer, Xavier
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p. 7521 - 7527
(2020/03/24)
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- Carbene-Catalyzed Formal [3+3] Cycloaddition Reaction for Access to Substituted 2-Phenylbenzothiazoles
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A carbene-catalyzed oxidative cycloaddition reaction is developed for efficient access to multi-functionalized 2-phenylbenzothiazoles. A broad scope of heavily substituted arenes bearing 2-benzothiazole groups have been prepared in good to excellent yields. The remote C(sp2)–H bond in the substituted arene products can be activated by Pd catalysts in regio-selective fashion with the direction of the 2-benzothiazole groups.
- Ni, Zhibin,Mou, Chengli,Zhu, Xun,Qi, Puying,Yang, Song,Chi, Yonggui Robin,Jin, Zhichao
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p. 492 - 495
(2020/01/24)
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- Arene Trifunctionalization with Highly Fused Ring Systems through a Domino Aryne Nucleophilic and Diels–Alder Cascade
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A convenient and efficient domino aryne process was developed under transition-metal-free conditions to generate a range of tetra- and pentacyclic ring systems. This transformation was realized via a 1,2-benzdiyne through a nucleophilic and Diels–Alder reaction cascade using styrene as the diene moiety. Three new chemical bonds, namely one C?N and two C?C bonds, and two benzofused rings could be constructed concomitantly, which was made possible by distinct chemoselective control at both the 1,2-aryne and 2,3-aryne stages. Moreover, in-depth studies were carried out on the domino aryne precursors and controlling the diastereoselectivity.
- He, Jia,Jia, Zizi,Tan, Hongcheng,Luo, Xiaohua,Qiu, Dachuan,Shi, Jiarong,Xu, Hai,Li, Yang
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p. 18513 - 18518
(2019/11/19)
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- Diaminodiphosphine tetradentate ligand and ruthenium complex thereof, and preparation methods and applications of ligand and complex
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The invention discloses a diaminodiphosphine tetradentate ligand and a ruthenium complex thereof, and preparation methods and applications of the ligand and the complex, and provides a ruthenium complex represented by a formula I, wherein L is a diaminodiphosphine tetradentate ligand represented by a formula II, and X and Y are respectively and independently chlorine ion, bromine ion, iodine ion,hydrogen negative ion or BH4. According to the present invention, the ruthenium complex exhibits excellent catalytic activity in the catalytic hydrogenation reactions of ester compounds, has high yield and high chemical selectivity, is compatible with conjugated and non-conjugated carbon-carbon double bond, carbon-carbon triple bond, epoxy, halogen, carbonyl and other functional groups, and hasgreat application prospects.
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Paragraph 0320-0323
(2019/11/04)
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- Manganese-Catalyzed Dual-Deoxygenative Coupling of Primary Alcohols with 2-Arylethanols
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Reported herein is a general and efficient dual-deoxygenative coupling of primary alcohols with 2-arylethanols catalyzed by a well-defined Mn/PNP pincer complex. This reaction is the first example of the catalytic dual-deoxygenation of alcohols using a non-noble-metal catalyst. Both deoxygenative homocoupling of 2-arylethanols (17 examples) and their deoxygenative cross-coupling with other primary alcohols (20 examples) proceeded smoothly to form the corresponding alkenes by a dehydrogenation and deformylation reaction sequence.
- Wang, Yujie,Shao, Zhihui,Zhang, Kun,Liu, Qiang
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p. 15143 - 15147
(2018/11/01)
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- Carbene-catalyzed enal γ-carbon addition to α-ketophosphonates for enantioselective access to bioactive 2-pyranylphosphonates
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A carbene-catalyzed enantioselective [4+2] cycloaddition reaction between α,β-unsaturated aldehydes and α-ketophosphonates is developed. The reaction affords chiral 2-pyranylphosphonates with excellent enantioselectivities. The optically enriched phosphonate products bear multiple functional groups, including unsaturated lactone and phosphonate moieties that often lead to unique bio-activities. Preliminary studies show that the products from our reactions exhibit anti-bacterial (X. oryzae pv. oryzae) and anti-viral (Tobacco Mosaic Virus) activities for potential use in plant protection.
- Sun, Jun,He, Fangcheng,Wang, Zhongyao,Pan, Dingwu,Zheng, Pengcheng,Mou, Chengli,Jin, Zhichao,Chi, Yonggui Robin
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supporting information
p. 6040 - 6043
(2018/06/18)
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- Gold-Catalyzed [2,3]-Sigmatropic Rearrangement: Reaction of Aryl Allyl Alcohols with Diazo Compounds
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A gold-catalyzed [2,3]-sigmatropic rearrangement reaction has been developed. The intermolecular rearrangement occurs between in situ generated donor-acceptor gold-carbenes and cinnamyl alcohols via tandem oxonium ylide formation. The desired rearranged product has been accomplished selectively over more conventional O-H insertion, cyclopropanation, cycloaddition, and C-H functionalization products under mild, open-air conditions. The scope of the work has been illustrated by synthesizing a new class of substrates that can be used for constructing complex molecular targets.
- Rao, Santhosh,Prabhu, Kandikere Ramaiah
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supporting information
p. 846 - 849
(2017/02/26)
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- METHOD OF FORMING A MULTI-SUBSTITUTED BENZENE COMPOUND
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The invention relates to a method of forming a multi-substituted benzene compound. In particular, the method involves benzene construction via organocatalytic formal [3+3] cycloaddition reaction.
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- Green and Rapid Access to Benzocoumarins via Direct Benzene Construction through Base-Mediated Formal [4+2] Reaction and Air Oxidation
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Benzocoumarin is an important structural motif widely found in natural products and synthetic molecules. Traditional methods for the synthesis of benzocoumarins and their derivatives require multiple steps, typically with an intramolecular ester forming reaction to make the lactone ring as the last step. Another major method involves transition metal-catalyzed coupling or carbon-hydrogen bond activation reactions starting with pre-existing aryl frameworks in the substrates. Here we report a new strategy for the green and rapid access to benzocoumarins and their derivatives. Our method uses readily available unsaturated aldehydes and coumarins as the substrates and air as the green oxidant. The overall reaction proceeds through a formal [4+2] process to construct a new benzene ring and thus to afford benzocoumarins in essentially a single step. No metal catalysts were used; no toxic or expensive reagents were involved. The power of our new approach is further demonstrated in a concise formal total synthesis of cannabinol, a bioactive natural product.
- Mou, Chengli,Zhu, Tingshun,Zheng, Pengcheng,Yang, Song,Song, Bao-An,Chi, Yonggui Robin
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p. 707 - 712
(2016/03/09)
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- Silver Tetrafluoroborate-Catalyzed Oxa-Diels-Alder Reaction between Electrically Neutral Dienes and Aldehydes
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Chemoselective oxa-Diels-Alder reactions between electrically neutral 1,3-dienes and various aldehydes were achieved using the commercially available silver tetrafluoroborate (AgBF4) as catalyst. This catalytic process has high functional group tolerance. Heteroatoms at the β-position of the aryl aldehydes can greatly promote the reactivity of the substrates even with heterocyclic aldehydes that were previously believed to be unreactive for the oxa-Diels-Alder reaction. In addition, acroleins with β-heteroatom substitution are also good substrates. High chemoselectivity and regioselectivity were achieved at room temperature for the oxa-Diels-Alder reaction between acroleins and stoichiometric simple 1,3-dienes.
- Zou, Xiaodong,Yang, Lizheng,Liu, Xiangli,Sun, Hao,Lu, Hongjian
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p. 3040 - 3046
(2015/11/03)
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- Oxidative γ-addition of enals to trifluoromethyl ketones: Enantioselectivity control via lewis acid/n-heterocyclic carbene cooperative catalysis
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An oxidative γ-functionalization of enals under N-heterocyclic carbene (NHC) catalysis to give unsaturated δ-lactones is disclosed. Enantioselectivity control involving the relatively remote enal γ-carbon was achieved via Lewis acid [Sc(OTf)3 or combined Sc(OTf) 3/Mg(OTf)2] and NHC cooperative catalysis.
- Mo, Junming,Chen, Xingkuan,Chi, Yonggui Robin
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p. 8810 - 8813
(2012/07/02)
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- Electrocyclization of oxatrienes in the construction of structurally complex pyranopyridones
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Application of a tandem Knoevenagel/6π-electrocyclization sequence is able to produce highly substituted pyranopyridones from moderate to high yields in a one-step reaction. High diasteroselectivity is observed in some cases and was rationalized on the basis of the thermodynamic control of the evidenced reversibility of a 6π-electrocyclization reaction. Numerous examples are provided establishing a novel entry in natural product-like structures of pyranopyridone alkaloids.
- Fotiadou, Anna D.,Zografos, Alexandros L.
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p. 5664 - 5667
(2013/01/15)
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- Ruthenium-catalyzed asymmetric transfer hydrogenation of allylic alcohols by an enantioselective isomerization/transfer hydrogenation mechanism
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Reducing hazards: A asymmetric transfer hydrogen reaction was developed to reduce prochiral allylic alcohols in high yield and excellent enantioselectivity (see example). Mechanistic studies indicate a novel enantioselective isomerization/transfer hydrogenation mechanism. This new reaction is much safer than high-pressure hydrogenation using H2 gas. Copyright
- Wu, Ruoqiu,Beauchamps, Marie G.,Laquidara, Joseph M.,Sowa Jr., John R.
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supporting information; experimental part
p. 2106 - 2110
(2012/04/11)
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- Development of an intramolecular aryne ene reaction and application to the formal synthesis of (±)-crinine
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A general and high yielding annulation strategy for the synthesis of various carbo- and heterocycles, based on an intramolecular aryne ene reaction is described. It was found that the geometry of the olefin is crucial to the success of the reaction, with exclusive migration of the trans-allylic-H taking place. Furthermore, the electronic nature of the aryne was found to be important to the success of the reaction. Deuterium labeling studies and DFT calculations provided insight into the reaction mechanism. The data suggests a concerted asynchronous transition state, resembling a nucleophilic attack on the aryne. This strategy was successfully applied to the formal synthesis of the ethanophenanthridine alkaloid (±)-crinine.
- Candito, David A.,Dobrovolsky, Dennis,Lautens, Mark
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supporting information
p. 15572 - 15580
(2012/11/07)
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- Mild and tunable benzoic acid catalysts for rearrangement reactions of allylic alcohols
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An efficient and simple catalytic method for the isomerization of readily prepared allylic alcohols is described. We focus particularly on cyclic examples and the synthesis of unusual enyne and dienols. The benzoic acid catalysts employed are commercially available and very inexpensive and can be tuned for reactivity and substrate sensitivity.
- McCubbin, J. Adam,Voth, Samantha,Krokhin, Oleg V.
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experimental part
p. 8537 - 8542
(2011/12/14)
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- Intramolecular aryne-ene reaction: Synthetic and mechanistic studies
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Although the chemistry of arynes is well developed, some challenges still remain. The ene reaction of arynes has not gained widespread use in synthesis as a result of poor yields and selectivity. A general, high yielding and selective intramolecular aryne-ene reaction is described providing various benzofused carbo- and heterocycles. Mechanistic data is presented, and a rationale for the resulting stereochemistry is discussed.
- Candito, David A.,Panteleev, Jane,Lautens, Mark
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supporting information; experimental part
p. 14200 - 14203
(2011/10/31)
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- Trapping of active methylene intermediates with alkenes, indoles or thiols: Towards highly selective multicomponent reactions
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In this paper, a basic method to access new multicomponent reactions (MCRs) is reported. The mechanism of these MCRs is based on the trapping of methylene intermediates, formed in situ by reaction of formaldehyde with electron-rich carbons, with alkene, thiol or indole derivatives. According to our strategy, a wide range of valuable skeletons has been obtained in a one-pot reaction, thus allowing a minimization of waste, cost and labor. The presented methodology exhibits a broad substrate scope and electron-rich carbons in the α-position of a hydroxy or carbonyl group were found to be particularly efficient. More generally, this work offers new tools for creating molecular complexity and diversity from one of the simplest organic building blocks, formaldehyde.
- Gu, Yanlong,Barrault, Joel,Jerome, Francois
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scheme or table
p. 3269 - 3278
(2010/04/24)
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- Synthesis and biological activity of permethrinic acid analogs containing various substituents in position 2 of the cyclopropane ring
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A number of permethrinic acid ethyl ester derivatives having various substituents [Et, Pr, Ph, Ph(CH2) n (n = 1, 2), etc.] in position 2 of the cyclopropane ring were synthesized, and their insecticidal acivity against typhoid flies, rice weevils, and bean aphides, as well as juvenoid activity on flour beetle chrysalises, was studied. The newly synthesized compounds turned out to exhibit weak insecticidal activity against standard insects but pronounced juvenile hormone activity, which differentiates them from permethrinic acid esters.
- Mirzabekova,Kuz'mina,Lukashov,Sokolova,Golosov,Kazakov,Perlova,Potapova,Kheinman,Ivanova
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experimental part
p. 1139 - 1149
(2009/09/25)
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- A simple strategy for spirocyclopentannulation of cyclic ketones. Formal total synthesis of (±)-acorone
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A general and simple methodology for spirocyclopentannulation of cyclic ketones (or 4,4-disubstituted cyclopentenones from acyclic ketones) and its application in the synthesis of the spirodienone 7 via a prochiral precursor constituting a formal total synthesis of (±)-acorone (6), are described.
- Srikrishna, Adusumilli,Kumar, P. Praveen,Viswajanani, Ranganathan
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p. 1683 - 1686
(2007/10/03)
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- Regioselectivity of Radical-induced Bond Cleavages in Epoxides
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Radical-induced carbon-carbon and carbon-oxygen bond cleavage reactions in a highly substituted epoxide, and in epoxides fused to other rings are reported.Substitution at the site of the developing radical assists C-C bond cleavage.In ring-fused epoxides, C-C bond cleavage was not seen where stereoelectronic factors oppose it.
- Murphy, John A.,Patterson, Christopher W.
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p. 405 - 410
(2007/10/02)
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- New Syntheses of Isomerically Pure Allyl and Propargyl Cyanides by Isocyanide-Cyanide Rearrangement
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A new route for the synthesis of isomerically pure allyl and propargyl cyanides has been developed.Allylic amines are synthesized from the corresponding alcohols by Mitsunobu or by Overman reaction.Formylation with formic acid derivatives provides N-substituted formamides, which are dehydrated to isocyanides. 1,2-Sigmatropic rearrangement by flash pyrolysis provides the isomerically pure allyl and propargyl cyanides. Key Words: Isocyanide-cyanide rearrangment / Cyanides, allyl- and propargyl-
- Wolber, Erwin K. A.,Schmittel, Michael,Ruechardt, Christoph
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p. 525 - 532
(2007/10/02)
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