- Copper-Catalyzed 1,1-Boroalkylation of Terminal Alkynes: Access to Alkenylboronates via a Three-Component Reaction
-
A copper-catalyzed three-component reaction of terminal alkynes, diazo compounds, and B2pin2 to prepare trisubstituted alkenylboronates has been developed. This difunctionalization of alkynes selectively occurs at the terminal carbon atom and proceeds via
- Li, Ziyong,Sun, Jiangtao
-
supporting information
p. 3706 - 3711
(2021/05/31)
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- Room Temperature Allenation of Terminal Alkynes with Aldehydes
-
A gold-catalyzed room temperature allenation of terminal alkynes (ATA) with aldehydes affording 1,3-disubstituted allenes with diverse functional groups has been developed by identifying a gold(I) catalyst and an amine. The practicality of this reaction has been demonstrated by a ten gram-scale synthesis and the synthetic potentials have been demonstrated via various transformations and formal total synthesis of (?)-centrolobine. Mechanistic studies revealed that the gold catalyst, the aldehyde effect, the fluoroalkyl hydroxyl solvent (TFE or HFIP) and the structure of amine are vital in this room temperature ATA reaction.
- Cui, Yifan,Li, Can,Ma, Shengming,Xiao, Junzhe,Xu, Haibo,Zhai, Yizhan,Zhang, Xue
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supporting information
p. 25708 - 25713
(2021/11/09)
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- Trifluoromethylation of Allenes: An Expedient Access to α-Trifluoromethylated Enones at Room Temperature
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A silver(I) catalyzed regioselective trifluoromethylation of allenes using Langlois's salt (NaOSOCF3) is demonstrated. This transformation enables direct expedient access to α-trifluoromethylated acroleins, which are valuable synthons for a number of pharmaceuticals and agrochemicals containing vinyl-CF3 moieties. Versatility of this trifluoromethylation method has been established with good yield and excellent regioselectivity. Preliminary experiments and computational studies were carried out to elucidate the mechanistic insight of this protocol.
- Brochetta, Massimo,Borsari, Tania,Gandini, Andrea,Porey, Sandip,Deb, Arghya,Casali, Emanuele,Chakraborty, Arka,Zanoni, Giuseppe,Maiti, Debabrata
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p. 750 - 753
(2019/01/04)
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- A convenient access to allylic triflones with allenes and triflyl chloride in the presence of (EtO)2P(O)H
-
A simple method for the preparation of allylic triflones from allenes and triflyl chloride in the presence of (EtO)2P(O)H has been developed. The features of this reaction are catalyst-free and simple starting substrates. This method tolerates diverse functional groups and substituted allylic triflones are obtained in moderate to good yields.
- Ni, Jixiang,Jiang, Yong,An, Zhenyu,Lan, Jingfeng,Yan, Rulong
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supporting information
p. 7343 - 7345
(2019/06/27)
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- Matched Coupling of Propargylic Carbonates with Cyclopropanols
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The ring opening-coupling reaction of cyclopropanols with propargylic carbonates affording synthetically attractive allenyl ketones has been developed. The mechanism involves the ligand-exchange reaction of in situ formed allenyl palladium methoxide with cyclopropanols followed by carbon-carbon bond cleavage and reductive elimination. The reactions proceeded smoothly under mild reaction conditions with Pd(0)/XPhos catalysis in the absence of any external base and displayed a wide scope and application to a steroidal skeleton. The efficiency of chirality transfer and synthetic utility of the allene products have also been demonstrated.
- Wu, Penglin,Jia, Minqiang,Lin, Weilong,Ma, Shengming
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supporting information
p. 554 - 557
(2018/02/10)
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- Fluorinative Rearrangements of Substituted Phenylallenes Mediated by (Difluoroiodo)toluene: Synthesis of α-(Difluoromethyl)styrenes
-
Phenylallenes undergo fluorinative rearrangement upon the action of (difluoroiodo)toluene in the presence of 20 mol % BF3?OEt2 to yield α-difluoromethyl styrenes. This unprecedented reaction was entirely chemoselective for the internal allene π bond, and showed remarkable regioselectivity during the fluorination event. Substituted phenylallenes, phenylallenes possessing both phenyl- and α-allenyl substituents, and diphenylallenes were investigated, and good functional-group compatibility was observed throughout. The ease with which allenes can be prepared on a large scale, and the operational simplicity of this reaction allowed us to rapidly access fluorine-containing building blocks that have not been accessed by conventional deoxyfluorination strategies.
- Zhao, Zhensheng,Racicot, Léanne,Murphy, Graham K.
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supporting information
p. 11620 - 11623
(2017/09/11)
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- Stereoselective annulation between an allene, an alkene, and two nitrosoarenes to access bis(isoxazoliodine) derivatives
-
This work reports metal-free annulations between one allene, two nitrosoarenes and one electron-deficient alkene to afford bis(isoxazolidine) derivatives stereoselectively. This process involves an initial formation of isoxazolidin-4-imine oxides, followe
- Sharma, Pankaj,Jadhav, Prakash D.,Skaria, Manisha,Liu, Rai-Shung
-
supporting information
p. 9389 - 9397
(2017/11/22)
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- Iodothiocyanation/Nitration of Allenes with Potassium Thiocyanate/Silver Nitrite and Iodine
-
Direct strategies for the iodothiocyanation and iodonitration of allenes have been developed. In this process, potassium thiocyanate/silver nitrite and molecular iodine are used as the source of SCN, ONO2and iodine to provide the desired products in moderate to good yields with high stereoselectivity. (Figure presented.).
- Yang, Xiaodong,She, Yue,Chong, Ya,Zhai, Huichun,Zhu, He,Chen, Baohua,Huang, Guosheng,Yan, Rulong
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supporting information
p. 3130 - 3134
(2016/10/09)
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- Enantioselective A3 Reactions of Secondary Amines with a Cu(I)/Acid-Thiourea Catalyst Combination
-
Pyrrolidine and related amines undergo asymmetric A3 reactions in the presence of copper iodide and an easily accessible cocatalyst possessing both a carboxylic acid and a thiourea moiety. Propargylamines are obtained with up to 96% ee, and catalyst loadings can be as low as 1 mol %. Pyrrolidine-derived propargylamines, in the absence of directing groups, can be transformed to the corresponding allenes without loss of enantiopurity.
- Zhao, Chenfei,Seidel, Daniel
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p. 4650 - 4653
(2015/04/27)
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- Ligandless Regioselective Hydrosilylation of Allenes Catalyzed by Gold Nanoparticles
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The first example of Au-catalyzed hydrosilylation of allenes is presented using recyclable gold nanoparticles as catalyst, without the requirement of any external ligands or additives. The hydrosilane addition takes place on the more substituted double bond of terminal allenes in a highly regioselective manner. The observed regioselectivity/reactivity modes are attributed to steric and electronic factors.
- Kidonakis, Marios,Stratakis, Manolis
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supporting information
p. 4538 - 4541
(2015/09/28)
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- Zinc salt promoted diastereoselective synthesis of chiral propargylamines using chiral piperazines and their enantioselective conversion into chiral allenes
-
Zinc chloride catalyzed reactions of chiral piperazine derivatives 4a-d with 1-alkynes and aldehydes give chiral propargylamines in 67-95 % yields with up to 99:1 dr. The chiral propargylamines are converted into chiral allenes by using zinc bromide in sh
- Periasamy, Mariappan,Reddy, Polimera Obula,Edukondalu, Athukuri,Dalai, Manasi,Alakonda, Laxman M.,Udaykumar, Bantu
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p. 6067 - 6076
(2015/03/30)
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- Kinetics and mechanism of the racemization of aryl allenes catalyzed by cationic gold(i) phosphine complexes
-
The kinetics of the racemization of aromatic 1,3-disubstituted allenes catalyzed by gold phosphine complexes has been investigated. The rate of gold-catalyzed allene racemization displayed first-order dependence on allene, and catalyst concentration and k
- Harris, Robert J.,Nakafuku, Kohki,Widenhoefer, Ross A.
-
supporting information
p. 12245 - 12254
(2015/03/31)
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- Palladium-catalyzed insertion of an allene into an aminal: Aminomethylamination of allenes by C-N bond activation
-
A new and atom-economic palladium-catalyzed aminomethylamination of allenes with aminals by C-N bond activation is described. This direct and operationally simple method provides a fundamentally novel approach for the synthesis of 1,3-diamines. Mechanistic studies suggest that a unique cationic π-allylpalladium complex containing an aminomethyl moiety is generated as a key intermediate through the carbopalladation of the allene with a cyclometalated palladium-alkyl species.
- Hu, Jianhua,Xie, Yinjun,Huang, Hanmin
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supporting information
p. 7272 - 7276
(2014/07/21)
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- Cyclometallated gold(III) complexes as effective catalysts for synthesis of propargylic amines, chiral allenes and isoxazoles
-
A series of cyclometallated gold(III) complexes [Au(CN)Cl2] 1a-l (HCN=arylpyridines) and a PEG-linked complex 1m were synthesized. Complexes 1a-m are effective in catalyzing the synthesis of propargylic amines, chiral allenes and isoxazoles. Six-membered ring cyclometallated gold(III) complexes 1f-l exhibited higher catalytic activity than five-membered ring cyclometallated gold(III) complexes 1a-e. The diastereoselectivity of propargylic amines could be tuned by using chiral aldehyde and/or amine substrates. Excellent enantioselectivities (90-98% ee) were achieved in chiral allene synthesis. Chiral allene racemization could be minimized by using 1f as catalyst. The PEG-linked catalyst 1m is the most catalytically active towards synthesis of propargylic amines, in which case a product turnover of 900 was achieved. Moreover, 1m could be repeatedly used for 12 reaction cycles, leading to an overall turnover number of 872. Copyright
- Kung, Karen Ka-Yan,Lo, Vanessa Kar-Yan,Ko, Hok-Ming,Li, Gai-Li,Chan, Pui-Ying,Leung, King-Chi,Zhou, Zhongyuan,Wang, Ming-Zhong,Che, Chi-Ming,Wong, Man-Kin
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p. 2055 - 2070
(2013/08/23)
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- Copper(I) halide promoted diastereoselective synthesis of chiral propargylamines and chiral allenes using 2-dialkylaminomethylpyrrolidine, aldehydes, and 1-alkynes
-
Copper bromide promoted reactions of aldehydes, 1-alkynes, and chiral 2-dialkylaminomethylpyrrolidine at 25 C give the corresponding chiral propargylamine derivatives in up to 96% yield and 99:1 dr that are readily converted to the corresponding disubstit
- Gurubrahamam, Ramani,Periasamy, Mariappan
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p. 1463 - 1470
(2013/03/28)
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- Enantioselective synthesis of both enantiomers of chiral allenes using chiral N-methylcamphanyl piperazine templates
-
The reaction of unsubstitued camphanyl-piperazine 4 with ZnCl2, phenylacetylene, and benzaldehyde in toluene gave the corresponding dipropargylamine (i.e., 15) with opposite configurations at the newly formed stereogenic centres, which, upon re
- Periasamy, Mariappan,Reddy, Polimera Obula,Sanjeevakumar, Nalluri
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p. 3866 - 3875
(2013/07/11)
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- CuI-catalyzed cross-coupling of N-tosylhydrazones with terminal alkynes: Synthesis of 1,3-disubstituted allenes
-
A CuI-catalyzed synthesis of 1,3-disubstituted allenes from 1-alkynes by the reaction with various N-tosylhydrazones has been developed. This method, which uses readily available starting materials and is operationally simple, offers 1,3-disubstituted all
- Hossain, Mohammad Lokman,Ye, Fei,Zhang, Yan,Wang, Jianbo
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p. 1236 - 1241
(2013/04/10)
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- Mild-condition synthesis of allenes from alkynes and aldehydes mediated by tetrahydroisoquinoline (THIQ)
-
A practical 1,2,3,4-tetrahydroisoquinoline (THIQ)-mediated synthesis of 1,3-disubstituted allenes from terminal alkynes and aldehydes under mild conditions in the presence of CuBr first and then ZnI2 was reported. This telescoped allene synthes
- Jiang, Guo-Jie,Zheng, Qin-Heng,Dou, Meng,Zhuo, Lian-Gang,Meng, Wei,Yu, Zhi-Xiang
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p. 11783 - 11793
(2014/01/06)
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- Transition-metal-free Suzuki-Miyaura coupling reaction of arylpropargylic bromides with aryl- and alkenylboronic acids
-
In the absence of transition-metal catalyst, Suzuki-Miyaura coupling reaction between aryl- and alkenylboronic acids and arylpropargylic bromides proceeded to give the corresponding acetylenic products selectively. Georg Thieme Verlag Stuttgart New York.
- Ueda, Mitsuhiro,Nishimura, Kota,Ryu, Ilhyong
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p. 1683 - 1686
(2013/09/02)
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- Highly enantioselective synthesis of chiral allenes by sequential creation of stereogenic center and chirality transfer in a single pot operation
-
Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent chirality transfer via an intramolecular hydride shift to produce chiral allenes with high enantiomeric purities.
- Periasamy, Mariappan,Sanjeevakumar, Nalluri,Dalai, Manasi,Gurubrahamam, Ramani,Reddy, Polimera Obula
-
supporting information; experimental part
p. 2932 - 2935
(2012/08/28)
-
- Kinetics and mechanism of gas-phase pyrolysis of ylides. Part 3. 1 Thermal reactivity of α-carbonyl- and thiocarbonyl-stabilized methylenetriphenylphosphoranes
-
Fourteen ketone/thione-stabilized triphenylphosphonium methylides were subjected to conventional gas-phase and flash vacuum pyrolysis (FVP). The kinetics of the first-order thermal gas-phase reactions of all these compounds were investigated over 360-653K temperature range. The values of the Arrhenius logA and energy of activation of these ylides averaged 11.52±0.34s -1 and 133.20±3.14kJmol-1, respectively. The products of sealed-tube (static) and FVP were analyzed and compared. A mechanism is proposed to account for the products of reaction. The rate constants [k (s-1)] of the substrates at 500K were calculated and used to substantiate the proposed mechanism of pyrolysis, and to rationalize the thermal gas-phase reactivities of the ylides under study.
- Al-Bashir, Rasha F.,Al-Awadi, Nouria A.,El-Dusouqui, Osman M. E.
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p. 311 - 319
(2012/04/17)
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- Gold(I)-catalyzed enantioselective intermolecular hydroarylation of allenes with indoles and reaction mechanism by density functional theory calculations
-
Chiral binuclear gold(I) phosphine complexes catalyze enantioselective intermolecular hydroarylation of allenes with indoles in high product yields (up to 90 %) and with moderate enantioselectivities (up to 63%ee). Among the gold(I) complexes examined, be
- Wang, Ming-Zhong,Zhou, Cong-Ying,Guo, Zhen,Wong, Ella Lai-Ming,Wong, Man-Kin,Che, Chi-Ming
-
experimental part
p. 812 - 824
(2011/10/02)
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- Coupling of n-tosylhydrazones with terminal alkynes catalyzed by copper(i): Synthesis of trisubstituted allenes
-
The easy way to allenes: An operationally simple reaction under mild conditions has led to the direct formation of trisubstituted allenes (see scheme; Ts=4-toluenesulfonyl). An unprecedented copper-carbene migratory insertion process seems to take place,
- Xiao, Qing,Xia, Ying,Li, Huan,Zhang, Yan,Wang, Jianbo
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p. 1114 - 1117
(2011/04/16)
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- Silver(i)-mediated highly enantioselective synthesis of axially chiral allenes under thermal and microwave-assisted conditions
-
Silver(i) salts mediated stereospecific transformation of optically active propargylamines to axially chiral allenes with excellent enantioselectivities (17 examples with 96-99% ee; one substrate with 91% ee) without subsequent racemization.
- Lo, Vanessa Kar-Yan,Zhou, Cong-Ying,Wong, Man-Kin,Che, Chi-Ming
-
supporting information; experimental part
p. 213 - 215
(2010/05/01)
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- Pd-catalyzed three-component coupling of N-Tosylhydrazone, terminal alkyne, and Aryl halide
-
A Pd-catalyzed three-component reaction of N-tosylhydrazone, terminal alkyne, and aryl halide follows a mechanism involving a sequence of Pd carbene migratory insertion-transmetalation-reductive elimination, leading to the formation of one sp2-sp3 C-C bond and one sp-sp 3 C-C bond.
- Zhou, Lei,Ye, Fei,Zhang, Yan,Wang, Jianbo
-
supporting information; experimental part
p. 13590 - 13591
(2010/12/29)
-
- Selective synthesis of allenes and alkynes through ligand-controlled, palladium-catalyzed decarboxylative hydrogenolysis of propargylic formates
-
Ligand-controlled regioselective palladium-catalyzed decarboxylative hydrogenolysis of propargylic formates is described. A wide range of allenes and alkynes were obtained by using either 1,2-diphenylphosphinoethane (DPPE) or 1,6-bisdiphenylphosphinohexane (DPPH) as a catalyst ligand.
- Ohmiya, Hirohisa,Yang, Mingyu,Yamauchi, Yoshihiro,Ohtsuka, Yuhki,Sawamura, Masaya
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supporting information; experimental part
p. 1796 - 1799
(2010/09/07)
-
- Gold(I)-catalyzed rearrangement of propargyl benzyl ethers: A practical method for the generation and in situ transformation of substituted allenes
-
A series of benzyl propargyl ethers react with a gold(I) catalyst to furnish variously substituted allenes via a 1,5-hydride shift/fragmentation sequence. This transformation is rapid and practical. It can be performed under very mild conditions (room temperature or 60 °C) using terminal as well as substituted alkyne substrates bearing a primary, secondary, or tertiary benzyl ether group. The allenes thus formed can be reacted in situ with an internal or external nucleophile, corresponding to an overall reductive substitution process, to produce more functionalized compounds.
- Bolte, Benoit,Odabachian, Yann,Gagosz, Fabien
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supporting information; experimental part
p. 7294 - 7296
(2010/08/05)
-
- Gold-catalyzed highly enantioselective synthesis of axially chiral allenes
-
Axially chiral allenes are synthesized from chiral propargylamines catalyzed by KAuCl4 in high yields (up to 93% yield) and excellent enantioselectivities (up to 97% ee) in CH3CN at 40 °C. The reaction has been applied to the synthes
- Lo, Vanessa Kar-Yan,Wong, Man-Kin,Che, Chi-Ming
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p. 517 - 519
(2008/09/19)
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- Enantiospecific synthesis of 1,3-disubstituted allenes by palladium-catalyzed coupling of propargylic compounds with arylboronic acids
-
An enantiospecific coupling of propargylic esters and carbonates with arylboronic acids has been developed using a palladium catalyst. Optically active 1,3-disubstituted allenes were synthesized with high enantiomeric excesses by carrying out the reaction
- Yoshida, Masahiro,Okada, Tatsuro,Shishido, Kozo
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p. 6996 - 7002
(2008/02/05)
-
- Lewis acid catalyzed propargylation of arenes with O-propargyl trichloroacetimidates: Synthesis of 1,3-diarylpropynes
-
(Chemical Equation Presented) The BF3·OEt 2-catalyzed Friedel-Crafts propargylation of aromatic compounds with O-propargyl trichloroacetimidates is highly efficient and affords 1,3-diarylpropyne derivatives in good yields.
- Li, Changkun,Wang, Jianbo
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p. 7431 - 7434
(2008/02/11)
-
- Ene reaction of arynes with alkynes
-
Arynes, generated in situ from ortho-silylaryl triflates, undergo ene reaction with alkynes possessing propargylic hydrogen in the presence of KF/18-crown-6 in THF at room temperature to give substituted phenylallenes. Various terminal and internal alkyne
- Jayanth, Thiruvellore Thatai,Jeganmohan, Masilamani,Cheng, Mu-Jeng,Chu, San-Van,Cheng, Chien-Hong
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p. 2232 - 2233
(2007/10/03)
-
- Asymmetric dihydroxylation of disubstituted allenes
-
Asymmetric dihydroxylation of 1,1-disubstituted and 1,3-disubstituted allenes can be used to synthesize chiral α-hydroxy ketones. We have also obtained α,α′-dihydroxy ketones with high enantioselectivity from 1,3-disubstituted allenes. Low conversion of the dihydroxylation of chiral allenes can be used as a kinetic resolution of sterically hindered allenes.
- Fleming, Steven A.,Liu, Renmao,Redd, J. Ty
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p. 8095 - 8098
(2007/10/03)
-
- Rearrangements and stereomutations of metallacycles derived from allenes and imidozirconium complexes
-
The mechanisms of the rearrangements and Stereoinversion of azametallacyclobutenes generated via [2+2] cycloaddition of allenes and imidozirconium complexes have been studied. Metallacycles derived from allenes bearing β-hydrogen atoms racemize at room temperature by reversible β-hydride elimination, a process which is also responsible for their eventual conversion to monoazadiene complexes. Metallacycles derived from diarylallenes racemize by reversible thermal bond homolysis at 95°C; racemization of these metallacycles is also catalyzed by mild oxidants.
- Michael, Forrest E.,Duncan, Andrew P.,Sweeney, Zachary K.,Bergman, Robert G.
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p. 1752 - 1764
(2007/10/03)
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- Highly chemoselective coupling of allenylstannanes with organic iodides promoted by Pd(PPh3)4/LiCl: An efficient method for the synthesis of substituted allenes
-
An efficient method for the preparation of various monosubstituted arylallenes, disubstituted allenes and alkenylallenes via palladium-catalyzed coupling of allenylstannanes with aryl iodides or alkenyl iodides is described. The coupling reaction was carr
- Huang, Chih-Wei,Shanmugasundaram, Muthian,Chang, Hao-Ming,Cheng, Chien-Hong
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p. 3635 - 3641
(2007/10/03)
-
- Synthesis of allenes from allylic alcohol derivatives bearing a bromine atom using a palladium(0)/diethylzinc system
-
A general and efficient synthesis of allenes using a palladium(0)/diethylzinc system is described. Treatment of mesylates or trichloroacetates of (E)- or (Z)-2-bromoalk-2-en-1-ols with diethylzinc in the presence of a catalytic amount of palladium(0) affords allenes bearing an aminoalkyl, alkyl, or aryl substituent(s) in good to high yields. No transfer of chirality from the stereogenic center carrying the mesyloxy group to the allene was observed.
- Ohno, Hiroaki,Miyamura, Kumiko,Tanaka, Tetsuaki,Oishi, Shinya,Toda, Ayako,Takemoto, Yoshiji,Fujii, Nobutaka,Ibuka, Toshiro
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p. 1359 - 1367
(2007/10/03)
-
- Synthesis of allenes by double Horner-Wadsworth-Emmons reaction
-
LDA treatment of aldehydes or ketone with alkenylphosphonates 2, prepared by Horner-Wadsworth-Emmons (HWE) reaction of methylenebisphosphonate 1 with aldehydes, afforded Baylis-Hillman reaction-type products 5 in high yields. HWE olefination of 5 with KH or KH-18-crown-6 as a base provided allenes in good yields. One-flask procedure was successfully developed starting from 1 to afford an allene in a reasonably good yield.
- Inoue, Hideki,Tsubouchi, Hiroshi,Nagaoka, Yasuo,Tomioka, Kiyoshi
-
-
- Allenes through Horner-Wadsworth-Emmons olefination of alkenylphosphonates
-
Mono- and di-substituted allenes 5 were synthesized by successive Horner-Wadsworth-Emmons olefination starting from methylene-bisphosphonate 1 and two carbonyl compounds. The key to success is KH or KH-18-crown-6 as a base for the second HWE olefination o
- Nagaoka, Yasuo,Inoue, Hideki,Tomioka, Kiyoshi
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p. 1843 - 1846
(2007/10/03)
-
- Magnesium cyclopropylidenes generated from 1-chlorocyclopropyl phenyl sulfoxides with Grignard reagents: Their properties, and a sulfoxide version of the Doering-Moore-Skattebol reaction
-
Magnesium cyclopropylidenes were generated from 1-chlorocyclopropyl phenyl sulfoxides with Grignard reagents (EtMgCl or i-PrMgCl) in THF at -78°C in high yields by a sulfoxide-magnesium exchange reaction. The generated magnesium cyclopropylidenes were found to be stable at below -60°C for at least 3 h. It was also found that the pyramidal inversion of the magnesium carbenoid was quite slow at below -60°C. When the sulfoxide-magnesium exchange reaction was conducted with phenylmagnesium chloride at 0°C, the 1-chlorocyclopropyl phenyl sulfoxides gave allenes in good to high yields.
- Satoh,Kurihara,Fujita
-
p. 5369 - 5375
(2007/10/03)
-
- Catalytic synthesis of allenes via isomerization of alkynes under phase- transfer catalyzed conditions
-
Catalytic isomerization of alkynes to allenes under phase-transfer catalyzed conditions is described. Commercially available quaternary ammonium salt such as tetrahexylammonium bromide acts as a very effective promoter to accelerate the reaction under mil
- Oku, Makoto,Arai, Shigeru,Katayama, Kimiko,Shioiri, Takayuki
-
p. 493 - 494
(2007/10/03)
-
- Integrated Chemical Process: One-Pot Double Elimination Method for Acetylenes
-
A novel one-pot process for synthesis of acetylenes has been achieved in which the following series of steps are integrated: addition of an α-anion of sulfone to aldehyde; trapping of the resulting adduct to incorporate a leaving group, and double elimination of this intermediate. Consolidation of Peterson elimination renders the process much simpler. This method provides a convenient and high-yielding access to a variety of enynes and polyynes as well as to functionally substituted aryl acetylenes containing halogen(s) or acetal groups, which are useful building blocks for aryl acetylene scaffolds. Iteration of the one-pot generation of acetylenic bonds provides a new metodology for the buildup of aryl acetylene skeletons.
- Orita, Akihiro,Yoshioka, Naonori,Struwe, Petra,Braier, Arnold,Beckmann, Anke,Otera, Junzo
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p. 1355 - 1363
(2007/10/03)
-
- Reactions of the Lithium Salts of the Tribenzylidenemethane Dianion, Diphenylacetone Dianion, and Related Compounds
-
Potentially synthetically useful reactions of the dilithium salts of the title dianions have been investigated. Electrophilic quenching with a variety of reagents usually leads to the expected products in good yield. Quenching the diphenylacetone dianion with 1 equiv of trimethylchlorosilane, however, gives a good yield of 1,3-diphenylallene obtained by formal elimination of a trimethylsiloxy anion from an intermediate monoquenched monoanion salt. NMR studies, however, do not reveal the intermediacy of the 1,3-diphenyl-2-(trimethylsiloxy)allyl anion but rather suggest that the initial reaction site is at carbon, rather than oxygen. Oxidation of the dianions leads either to ring closure or dimerization for the tribenzylidenemethane dianion and to dimerization for the diphenylacetone dianion. The dimerization reactions are stereospecific, both with respect to the two new stereocenters produced and for the double bonds of the bis-silyl enol ether products if the dimeric bis-enolate dianion products are quenched with trimethylchlorosilane.
- Witt, Ortrun,Mauser, Harald,Friedl, Thomas,Wilhelm, Dieter,Clark, Timothy
-
p. 959 - 967
(2007/10/03)
-
- α-Zincated phosphorus ylides
-
1,3-Dizincata-2,4-diphosphoniacyclobutane rearranges into a zincataphosphoniaindane which reacts with benzaldehyde to give 1,3-diphenylallene.
- Steiner, Matthias,Gruetzmacher, Hansjoerg,Prtizkow, Hans,Zsolnai, Laszlo
-
p. 285 - 286
(2007/10/03)
-
- Integrated chemical process. One-pot preparation of acetylenes by Peterson-sulfone elimination
-
Integration of silylation of α-sulfonyl carbanion, addition of the anion of the resulting α-silyl sulfone to aldehyde, Peterson elimination, and sulfone elimination leads to one-pot synthesis of acetylenes.
- Orita, Akihiro,Yoshioka, Naonori,Otera, Junzo
-
p. 1023 - 1024
(2007/10/03)
-
- The Mechanism of Double Olefination Using Titanium-Substituted Ylides
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The adduct 3, derived from TiCl3(OiPr) and (Me2N)3P=CH2, engages in a complicated set of interactions with NaN(SiMe3)2 and aldehydes, resulting in the requirement to use excess amounts of both reagents for the one-pot synthesis of allenes. When TiCl2(OiPr)2 is used instead, ligand substitution reactions with NaN(SiMe3)2 are diminished and so stepwise transformations can be accomplished without excess amounts of each reagent. The selective production of vinylphosphonium salts and byproduct titanium oxides from Ti-substituted ylides and aldehydes is proposed to arise from the presence of a chloride leaving group on the metal. Isolated vinylphosphonium compounds may be deprotonated with phenyllithium to give thermally sensitive allenic phosphoranes, which have been characterized by low temperature multinuclear NMR. The reaction of allenic phosphoranes with aldehydes affords oxaphosphetane and betaine intermediates which appear to interconvert upon warming to produce allene and phosphine oxide. Dimethylamino-substituted phosphorus components are required for high yields in both steps of the allene-forming process, presumably to boost the reactivity of the hindered Ti-substituted ylide reagents and to stabilize the allenic phosphorane unit so that it may be trapped by aldehyde. The placement of chiral groups on the phosphorus methylide or aldehyde components results in low levels of enantiomeric and diastereomeric induction, respectively, during allene formation. In two cases, the diastereomeric ratios of initially-formed oxaphosphetanes have been found to differ from the diastereomeric composition of their product allenes, offering examples of the phenomenon known as "stereochemical drift". However, oxaphosphetane/betaine formation from allenic phosphorane and aldehyde has been found to be irreversible, suggesting that an intramolecular betaine olefin isomerization is responsible for the loss of stereochemical integrity during the Wittig step.
- Reynolds, Kelly A.,Finn
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p. 2574 - 2593
(2007/10/03)
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- The Polarized Absoption Spectrum of 1,3-Diphenyl-1,2-propadiene: Interaction between Mutually Perpendicular Equivalent ?-Electronic Systems
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The polarized UV absorption spectrum of 1,3-diphenyl-1,2-propadiene (DPA) wasx measured in a stretched polymer film at 101 K, and the polarization directions of the lectronic absorption bands were determined.Pariser-Parr-Pople (PPP) calculations extended
- Okubo, Jun,Shimazaki, Takayasu,Sato, Shin-ichi,Shinozaki, Hiraku
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p. 1405 - 1411
(2007/10/02)
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- Palladium-catalyzed coupling of stannyl allenes with aryl iodides
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Substituted allenes are prepared by coupling stannyl allenes with aryl iodides under palladium(0) catalysis. A concise and versatile sequence starting from propargyl alcohols provides a route for the preparation of substituted allenes under extremely mild conditions.
- Aidhen,Braslau
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p. 789 - 797
(2007/10/02)
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- Stereochemistry of direct olefin formation from carbonyl compounds and lithiated heterocyclic sulfones
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The conditions for the title reaction were studied for the 2-benzothiazole and 2-pyridine series and for some examples in the 2-pyrimidine series.The olefin preparations were generally observed to be more efficient for 2-BT-sulfone systems.From the data of the hundred cases studied, it can be concluded that (E)-olefins are obtained: (i) from saturated BT-sulfones and aromatic aldehydes; and (ii) from benzylic BT-sulfones and branched saturated aldehydes (isobutyraldehyde, pivalaldehyde) or α,β-ethylenic or aromatic aldehydes. (Z)-olefins arise: (i) fom propargylic BT-sulfones and saturated or aromatic aldehydes; and (ii) from allylic or benzylic Pyr-sulfones and saturated aldehydes.Possible mechanisms for this new olefination procedure were examined. - heteroaromatic sulfones, organolithium derivatives, intramolecular ipso reactions, stereochemistry, elimination, olefination.
- Baudin, J. B.,Hareau, G.,Julia, S. A.,Lorne, R.,Ruel, O.
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p. 856 - 878
(2007/10/02)
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- Electron Demand in the Transition State of the Cyclopropylidene to Allene Ring Opening
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The electronic structure of the transition state for the cyclopropylidene to allene conversion has been probed.The methodology involved the relative rates of ring opening vs trapping by MeOH for a series of variously substituted 2,3-diarylcyclopropylidenes.With the assumption that the rate of trapping was unaffected by substituents, a Hammett correlation was constructed.The negative value (-0.72) for ρ indicated that the carbenic center attracts electron density in the ring-opening transition state, much like the cyclopropyl cation to allyl cation transition state.Temperature-dependent studies showed that the observed preference for ring opening was driven by entropy factors.Also, using reasonable estimates for the close to diffusion-controlled trapping activation enthalpies, the derived enthalpies for ring opening were in close agreement with the best theoretical values.
- Warner, Philip,Sutherland, Robert
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p. 6294 - 6300
(2007/10/02)
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- Allene Synthesis via Boron-stabilised Alkenyl Carbanions
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A new allene synthesis involving the boron-Wittig reaction of aldehydes with boron-stabilised carbanions is disclosed and its scope and limitations are explored.
- Pelter, Andrew,Smith, Keith,Jones, Kevin D.
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p. 747 - 748
(2007/10/02)
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