- Synthesis of alkyne derivatives of a novel triazolopyrazine as A 2A adenosine receptor antagonists
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A novel [1,2,4]triazolo[1,5-a]pyrazine core was synthesized and coupled with terminal acetylenes. The structure-activity relationship of the alkynes from this novel template was studied for their in vitro and in vivo adenosine A2A receptor antagonism. Selected compounds from this series were shown to have potent in vitro and in vivo activities against adenosine A 2A receptor. Compound 12, in particular, was found to be orally active at 3 mg/kg in both a mouse catalepsy model and a 6-hydroxydopamine- lesioned rat model.
- Yao, Gang,Haque, Serajul,Sha, Li,Kumaravel, Gnanasambandam,Wang, Joy,Engber, Thomas M.,Whalley, Eric T.,Conlon, Patrick R.,Chang, Hexi,Kiesman, William F.,Petter, Russell C.
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Read Online
- Further chemistry of ruthenium alkenyl acetylide complexes: Routes to allenylidene complexes via a series of electrophilic addition reactions
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The methyl substituents in the cationic allenylidene complexes trans-[Ru{C=C=C(Me)R}Cl(dppe)2]OTf ([1a?f]OTf) are readily deprotonated to give the corresponding alkenyl acetylide complexes trans-[Ru{C=CC(=CH2)R}Cl(dppe)2] (3; R = Me (a), Ph (b), cC5H10 (c), 4-MeS-C6H4 (d), cC4H3S (e), cC5H4N (f)). Similar chemistry is also observed from [Ru{C=C=C(Me)Ph}(dppe)Cp*]PF6 ([2b]PF6) and [Ru{C=C=C(Me)(4-MeS-C6H4)}(dppe)Cp*]PF6([2b]PF6), chosen to broaden the reaction scope, giving [Ru{C= CC(=CH2)Ph}(dppe)Cp*] (4b) and [Ru{C=C=C(CH2)(4-MeS-C6H4)}(dppe)Cp*] (4d). In turn, reactions of 3b,d and 4b,d with the [BF4]? salt of the electrophilic tritylium [CPh3]+ cation give the functionalized allenylidene complexes trans-[Ru{C=C=C(CH2CPh3)R}Cl(dppe)2]BF4 ([5b,d]BF4) and [Ru{C=C=C(CH2CPh3)R}(dppe)Cp*]BF4 ([6b,d]BF4) formed by addition of the electrophile to the remote vinylic carbon (C(δ)). Although trans-[Ru{C=C=C(CH2CPh3)Me}Cl(dppe)2]BF4 ([5a]BF4) could not be successfully purified from reactions of 3a with [CPh3]BF4, deprotonation of the crude product gave the Zaitsev vinyl product trans-[Ru{C=CC(=CHCPh3)Me}Cl(dppe)2] (7a) in good yield. The initial cycloheptatrienyl adducts formed from reactions of 3b,d and 4b,d with the tropylium salt [C7H7]BF4 undergo a ring-contraction process in chloroform solutions upon exposure to air, to give the styrene-like products trans-[Ru{C=C=C(R)C(H)=CHPh}Cl(dppe)2]BF4 ([10b,d]BF4) and [Ru{C=C= C(R)C(H)=CHPh}(dppe)Cp*]BF4 ([11b,d]BF4), through what is believed to be a radical mechanism mediated by triplet oxygen.
- Hall, Michael R.,Korb, Marcus,Moggach, Stephen A.,Low, Paul J.
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p. 2838 - 2853
(2020/10/02)
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- BTK Inhibitors and uses thereof
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The invention discloses a bruton's tyrosine kinase (BTK) inhibitor and use thereof. Specifically, the invention provides heteroaromatic compounds or stereoisomers, geometrical isomers, tautomers, racemates, nitrogen oxides, hydrates, solvates, metabolites and pharmaceutically acceptable salts or prodrugs thereof, and pharmaceutical compositions containing the heteroaromatic compounds; the invention also discloses use of the heteroaromatic compounds or the pharmaceutical compositions containing the heteroaromatic compounds in preparation of medicines; the medicines can be used for treating autoimmune diseases, inflammatory diseases or proliferative diseases.
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- Kinetic Resolution of Tertiary Propargylic Alcohols by Enantioselective Cu?H-Catalyzed Si?O Coupling
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A broad range of tertiary propargylic alcohols were kinetically resolved by catalyst-controlled enantioselective silylation. This non-enzymatic kinetic resolution is catalyzed by a Cu?H species and makes use of the commercially available precatalyst MesCu/(R,R)-Ph-BPE and a simple hydrosilane as the resolving reagent. Both alkyl,aryl- as well as dialkyl-substituted propargylic alcohols participate, and especially high selectivity factors are achieved when the alkyne terminus carries a TIPS group, which also enables facile post-functionalization in this position (s up to 207).
- Seliger, Jan,Dong, Xichang,Oestreich, Martin
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supporting information
p. 1970 - 1974
(2019/01/29)
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- Neighboring Carbonyl Group Assisted Oxyacetoxylation of Propargylic Carboxylates with Retention of Chirality under Metal Free Condition
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A metal-free oxyacetoxylation method of primary, secondary and tertiary propargylic carboxylates with retention of chirality was presented. The reaction proceeds through the intramolecular nucleophilic attack of the neighboring carbonyl group on an alkynyliodonium intermediate. The process is general with broad substrate scope and is amenable for application to a variety of propargyl carboxylates including those obtained from natural products. Insight into the mechanistic pathway by isotopic labelling (using H2O18 and D2O) and controlled experiments confirmed. (Figure presented.).
- Pradhan, Tapas R.,Mohapatra, Debendra K.
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p. 3605 - 3611
(2019/07/04)
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- Cycloisomerization of Conjugated Allenones into Furans under Mild Conditions Catalyzed by Ligandless Au Nanoparticles
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Au nanoparticles supported on TiO2 (1 mol %) catalyze the quantitative cycloisomerization of conjugated allenones into furans under very mild conditions. The reaction rate is accelerated by adding acetic acid (1 equiv), but the acid does not participate in the protodeauration step as in the corresponding Au(III)-catalyzed transformation. The process is purely heterogeneous, allowing thus the recycling and reuse of the catalyst effectively in several runs.
- Zorba, Leandros,Kidonakis, Marios,Saridakis, Iakovos,Stratakis, Manolis
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supporting information
p. 5552 - 5555
(2019/08/01)
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- Heterogeneous Acid-Catalyzed Racemization of Tertiary Alcohols
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Tertiary alcohols are important structural motifs in natural products and building blocks in organic synthesis but only few methods are known for their enantioselective preparation. Chiral resolution is one of these approaches that leaves one enantiomer (50 % of the material) unaffected. An attractive method to increase the efficiency of those resolutions is to racemize the unaffected enantiomer. In the present work, we have developed a practical racemization protocol for tertiary alcohols. Five different acidic resin materials were tested. The Dowex 50WX8 was the resin of choice since it was capable of racemizing tertiary alcohols without any byproduct formation. Suitable solvents and a biphasic system were investigated, and the optimized system was capable of racemizing differently substituted tertiary alcohols.
- G?rbe, Tamás,Lihammar, Richard,B?ckvall, Jan -E.
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- Base-Catalyzed Borylation/B-O Elimination of Propynols and B2pin2 Delivering Tetrasubstituted Alkenylboronates
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An efficient approach to tetrasubstituted alkenylboronates via a cascade borylation/B-O elimination of propynols and B2pin2 was disclosed. A series of tetrasubstituted alkenylboronates were readily furnished with this strategy in good yields, with further transformations leading to tetrasubstituted alkenes and β-diketones demonstrating the synthetic potential of the alkenylboronates constructed by this strategy as versatile intermediates in organic synthesis.
- Kuang, Zhijie,Chen, Haohua,Yan, Jianxiang,Yang, Kai,Lan, Yu,Song, Qiuling
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supporting information
p. 5153 - 5157
(2018/09/12)
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- Method for efficiently preparing alkynol
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The invention relates to a method for efficiently preparing alkynol, belongs to the field of preparation of chemical intermediates and chemicals, and particularly relates to a preparation method of alkynol. The preparation method comprises the following steps that 1, alkali metal is added into an anhydrous alcohols solvent; an alcohol-alkali metal solution is prepared; 2, a compound I is added into the alcohol-alkali metal solution; uniform stirring is performed; cooling is performed to be 0 DEG C or below; 3, acetylene is introduced through being metered at normal pressure; alkynol is obtained; 4, the alkynol solution after reaction is neutralized by ammonium chloride and a same alcohol mixed suspension system; 5, the neutralized mixed suspension system is filtered; after alcohols are recovered from filter liquid, reduced pressure distillation is performed to obtain an alkynol product. The method overcomes the defect that under the existing harsh reaction conditions of high pressure,liquid ammonia and the like, the solid potassium hydroxide feeding difficulty is avoided; under the ordinary pressure condition, the ketone compounds are converted into alkynol at high conversion rate. The method has the advantages of high conversion rate, simple process and good product purity.
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Paragraph 0036; 0037; 0038; 0043; 0044; 0045; 0046
(2018/12/14)
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- Direct Substitution of Secondary and Tertiary Alcohols to Generate Sulfones under Catalyst- and Additive-Free Conditions
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An environmentally benign protocol that affords propargylic sulfones containing highly congested carbon centers from easily accessible alcohols and sulfinic acids with water as the only byproduct is reported. The reaction proceeded via an in situ dehydrative cross-coupling process by taking advantage of the synergetic actions of multiple hydrogen bonds rather than relying on an external catalyst and/or additives to achieve high product distribution.
- Liu, Yanan,Xie, Peizhong,Sun, Zuolian,Wo, Xiangyang,Gao, Cuiqing,Fu, Weishan,Loh, Teck-Peng
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supporting information
p. 5353 - 5356
(2018/09/13)
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- Synthesis of Vinyl-, Allyl-, and 2-Boryl Allylboronates via a Highly Selective Copper-Catalyzed Borylation of Propargylic Alcohols
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An efficient methodology for the synthesis of vinyl-, allyl-, and (E)-2-boryl allylboronates from propargylic alcohols via Cu-catalyzed borylation under mild conditions is reported. In the presence of commercially available Cu(OAc)2 or Cu(acac)2 and Xantphos, the reaction affords the desired products in up to 92% yield with a broad substrate scope (43 examples). Isolation of an allenyl boronate as the reaction intermediate suggests that an insertion-elimination-type reaction, followed by borylcupration, is involved in the borylation of propargylic alcohols.
- Mao, Lujia,Bertermann, Rüdiger,Emmert, Katharina,Szabó, Kálmán J.,Marder, Todd B.
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supporting information
p. 6586 - 6589
(2017/12/26)
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- Ni-Catalyzed regio- and stereoselective addition of arylboronic acids to terminal alkynes with a directing group tether
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Addition of arylboronic acids to directing group tethered acetylenes in a regio and stereoselective manner using an inexpensive catalytic system is achieved for the first time to access highly sought after allyl/homoallyl alcohol/amine units. The apparent vinylnickel intermediate was successfully trapped by the Michael electrophiles to get defined tri- and tetra-substituted olefins. An interesting selectivity switch was observed with internal alkynes.
- Hari Babu, Madala,Ranjith Kumar, Gadi,Kant, Ruchir,Sridhar Reddy, Maddi
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supporting information
p. 3894 - 3897
(2017/04/04)
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- Metal- and Acid-Free Methyl Triflate Catalyzed Meyer-Schuster Rearrangement
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A novel metal- and acid-free preparation of synthetically useful α,β-unsaturated carbonyl compounds from propargyl alcohols has been realized. This Meyer-Schuster rearrangement process is effectively catalyzed by methyl triflate (20 mol%) to prepare a broad scope of conjugated E -enals and E -enones generally in good to excellent yields (up to 90%). This reaction procedure operates under mild conditions (70 °C), in air, with short reaction times (1 h). Moreover, a carbocation intermediate trapped by the solvent 2,2,2-trifluoroethanol was isolated during this transformation.
- Yang, Lu,Zeng, Qingle
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p. 3149 - 3156
(2017/07/12)
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- Complementary iron(II)-catalyzed oxidative transformations of allenes with different oxidants
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Substituent- and oxidant-dependent transformations of allenes are described. Given the profound influence of the substituent on the reactivity of allenes, the subtle differences in allene structures are manifested in the formation of diverse products when reacted with different electrophiles/oxidants. In general, reactions of nonsilylated allenes involve an allylic cation intermediate by forming a C-O bond, at the sp-hybridized C2, with either DDQ (2,3-dichloro-5,6-dicyano-p-benzoquinone) or TBHP (tert-butyl hydroperoxide), along with FeCl2·4 H2O (10 mol %). In contrast, silylated allenes favor the formation of propargylic cation intermediates by transferring the allenic hydride to the oxidant, thus generating 1,3-enynes (E1 product) or propargylic THBP ethers (SN1 product). The formation of these different putative cationic intermediates from nonsilylated and silylated allenes is strongly supported by DFT calculations. Profound impact: Iron(II)-catalyzed transformations of allenes induced by either DDQ or tBuOOH depend on the substituent on the allenes. Nonsilylated and silylated allenes show complementary reactivity upon exposure to DDQ and tBuOOH in the presence of an iron(II) catalyst. Nonsilylated allenes incorporate the oxidant at the sp-hybridized carbon, whereas the silylated allenes generate 1,4-dehydrogenated 1,3-enynes. DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoquinone.
- Sabbasani, Venkata R.,Lee, Hyunjin,Xia, Yuanzhi,Lee, Daesung
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supporting information
p. 1151 - 1155
(2016/01/20)
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- Construction of Chiral Tri- and Tetra-Arylmethanes Bearing Quaternary Carbon Centers: Copper-Catalyzed Enantioselective Propargylation of Indoles with Propargylic Esters
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Copper-catalyzed enantioselective propargylation of indoles with propargylic esters and sequential Huisgen cycloaddition with azides lead to the construction of chiral triarylmethanes, bearing a quaternary carbon center, with high to excellent enantioselectivities. The result described herein can be used in the enantioselective preparation of a tetraarylmethane.
- Tsuchida, Kouhei,Senda, Yasushi,Nakajima, Kazunari,Nishibayashi, Yoshiaki
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supporting information
p. 9728 - 9732
(2016/08/10)
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- Lewis acid catalyzed cascade reaction of 3-(2-benzenesulfonamide)propargylic alcohols to spiro[indene-benzosultam]s
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A highly efficient and convenient construction of the spiro[indene-benzosultam] skeleton from propargylic alcohols has been developed. The reaction proceeded in a Lewis acid catalyzed cascade process, including the trapping of allene carbocation with sulfonamide, electrophilic cyclization, and intramolecular Friedel-Crafts alkylation. In the presence of NIS or NBS, iodo/bromo-substituted spiro[indene-benzosultam]s could be prepared in excellent yields.
- Sun, Lang,Zhu, Yuanxun,Wang, Jing,Lu, Ping,Wang, Yanguang
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supporting information
p. 242 - 245
(2015/02/19)
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- Convenient and highly efficient routes to 2 H-chromene and 4-chromanone derivatives: Iodine-promoted and p-toluenesulfonic acid catalyzed cascade cyclizations of propynols
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A convenient strategy is presented for the easy preparation of a series of 2 H-chromenes under mild conditions through iodocyclization of readily accessible propynols. In addition, various 4-chromanones can be synthesized through a p-toluenesulfonic acid catalyzed cascade cyclization with high efficiency (yields up to 99%). Our developed reaction systems are proven to have good functional-group applicability and can be scaled up to gram quantities in satisfactory yields. These systems also provide a new synthetic strategy for two types of important flavonoid skeleton without using costly and toxic metal catalysts. Additionally, the resulting halides could be further exploited in subsequent palladium-catalyzed coupling reactions, so these compounds could act as potential intermediates for the construction of some valuable drug molecules.
- Qiu, Yi-Feng,Ye, Yu-Ying,Song, Xian-Rong,Zhu, Xin-Yu,Yang, Fang,Song, Bo,Wang, Jia,Hua, Hui-Liang,He, Yu-Tao,Han, Ya-Ping,Liu, Xue-Yuan,Liang, Yong-Min
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supporting information
p. 3480 - 3487
(2015/03/04)
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- Gold-catalyzed reactions of propargylic esters with vinylazides for the synthesis of Z- or E-configured buta-1,3-dien-2-yl esters
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Gold-catalyzed synthesis of buta-1,3-dien-2-yl esters by the reaction of propargyl esters with vinylazides is described; the reaction mechanism is postulated to involve a vinyl attack of vinylazides at alkenyl gold carbenes.
- Wagh, Sachin Bhausaheb,Liu, Rai-Shung
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supporting information
p. 15462 - 15464
(2015/10/20)
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- Fluoride-assisted activation of calcium carbide: A simple method for the ethynylation of aldehydes and ketones
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The fluoride-assisted ethynylation of ketones and aldehydes is described using commercially available calcium carbide with typically 5 mol % of TBAF·3H2O as the catalyst in DMSO. Activation of calcium carbide by fluoride is thought to generate an acetylide "ate"-complex that readily adds to carbonyl groups. Aliphatic aldehydes and ketones generally provide high yields, whereas aromatic carbonyls afford propargylic alcohols with moderate to good yields. The use of calcium carbide as a safe acetylide ion source along with economic amounts of TBAF·3H2O make this procedure a cheap and operationally simple method for the preparation of propargylic alcohols.
- Hosseini, Abolfazl,Seidel, Daniel,Miska, Andreas,Schreiner, Peter R.
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supporting information
p. 2808 - 2811
(2015/06/16)
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- Dehalogenation of functionalized alkyl halides in water at room temperature
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Alkyl bromides and chlorides can be reduced to the corresponding hydrocarbons utilizing zinc in the presence of an amine additive. The process takes place in water at ambient temperatures, enabled by a commercially available designer surfactant. The reaction medium can be readily recycled, and the amount of organic solvent invested for product isolation is minimal, leading to very low E Factors. This journal is
- Isley, Nicholas A.,Hageman, Matt S.,Lipshutz, Bruce H.
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supporting information
p. 893 - 897
(2015/03/04)
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- Silver(I)-catalyzed hydroazidation of ethynyl carbinols: Synthesis of 2-azidoallyl alcohols
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The hydroazidation of alkynes is the most straightforward pathway to synthetically useful vinyl azides. However, a general hydroazidation of alkynes remains elusive. Herein, a chemo- and regioselective transformation of ethynyl carbinols into vinyl azides is described. This reaction produces a wide variety of 2-azidoallyl alcohols with high efficiency and in good to excellent yields. These compounds constitute a new class of densely functionalized synthetic intermediates. Their synthetic potential has been demonstrated by further transformations into NH aziridines. The mechanistic aspects of the reaction will attract the attention of chemists working on alkyne chemistry and silver catalysis. The findings that are described in this paper represent significant advances in the regioselective hydroelementation of alkynes and open a new reaction manifold for exploitation. Azides and aziridines: The hydroazidation of unactivated alkynes by means of silver catalysis is described. A variety of ethynyl carbinols are capable of reacting with trimethylsilyl azide to produce 2-azidoallyl alcohols in good to excellent yields. The synthetic utility of 2-azidoallyl alcohols was demonstrated by further conversion into NH aziridines.
- Liu, Zhenhua,Liu, Jianquan,Zhang, Lin,Liao, Peiqiu,Song, Jinna,Bi, Xihe
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p. 5305 - 5309
(2014/06/09)
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- Palladium-catalyzed intermolecular [3 + 2] carbocyclization of alkynols and propiolates: An efficient entry to halo-cyclopentadienes
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A novel and efficient Pd-catalyzed intermolecular [3 + 2] carbocyclization of alkynols and electron-deficient alkynes for the synthesis of halo-cyclopentadienes (Cps) has been developed. The present protocol employs simple propargyl alcohols as the C3 group to participate in the cyclization reaction, providing a highly convenient and atom-economical entry to the halo-cyclopentadiene framework. The Royal Society of Chemistry.
- Gao, Yang,Wu, Wanqing,Huang, Huawen,Huang, Yubing,Jiang, Huanfeng
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supporting information
p. 846 - 848
(2014/01/06)
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- Br?nsted acid-catalyzed meyer-schuster rearrangement for the synthesis of α, β -unsaturated carbonyl compounds
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An efficient and simple protocol for the Meyer-Schuster rearrangement of propargyl alcohols into α,β-unsaturated carbonyl compounds has been developed using catalytic amounts of p-toluenesulfonic acid in 1,2-dichloroethane.
- Park, Jungmin,Yun, Jihee,Kim, Jaehyun,Jang, Dong-Jin,Park, Cheol Ho,Lee, Kooyeon
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supporting information
p. 1924 - 1929
(2014/07/07)
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- Bronsted acid mediated nitrogenation of propargylic alcohols: An efficient approach to alkenyl nitriles
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A novel and efficient approach to alkenyl nitriles from readily available propargylic alcohols has been developed. This nitrogenation reaction is transition-metal-free and could be conducted under air at ambient temperature, which makes this protocol promising and practical. Moreover, NH4Br is disclosed as an efficient additive to promote the stereoselectivity of this reaction. the Partner Organisations 2014.
- Huang, Xiaoqiang,Jiao, Ning
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supporting information
p. 4324 - 4328
(2014/06/23)
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- Alkynylation of aldehydes and ketones using the Bu4NOH/H 2O/DMSO catalytic composition: A wide-scope methodology
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The Favorsky reaction of a wide range of aldehydes and ketones with alkynes has been implemented under mild conditions (5-20 C). Using a Bu 4NOH/H2O/DMSO catalytic system, propargylic alcohols are formed cleanly in 39-93% (mostly 72-93%) yields and with ca. 100% selectivity. The method is suitable for aliphatic, aromatic, and heteroaromatic aldehydes and ketones, and for aliphatic, aromatic, and functionalized acetylenes. Thus, this represents the most general and efficient protocol to achieve the Favorsky reaction. Copyright
- Schmidt, Elena Yu.,Cherimichkina, Natalia A.,Bidusenko, Ivan A.,Protzuk, Nadezhda I.,Trofimov, Boris A.
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p. 4663 - 4670
(2014/08/05)
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- Au-catalyzed formation of functionalized quinolines from 2-alkynyl arylazide derivatives
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A new method for converting 2-alkynyl arylazide derivatives into functionalized polysubstituted quinolines following a gold-catalyzed 1,3-acetoxy shift/cyclization/1,2-group shift sequence has been developed. This transformation proceeds under mild reaction conditions, is efficient, and tolerates a large variety of functional groups.
- Gronnier, Colombe,Boissonnat, Guillaume,Gagosz, Fabien
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p. 4234 - 4237
(2013/09/12)
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- Pd(II)-catalyzed highly regio-and stereoselective assembly of C-C double bonds: An efficient method for the synthesis of 2,4-dihalo-1,3,5-trienes from alkynols
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A highly efficient method for the synthesis of 2,4-dihalo-1,3,5-trienes from alkynols was developed. This chemistry allows access to multiple conjugated double bonds in a single step with high stereoselectivity.
- Jiang, Huanfeng,Gao, Yang,Wu, Wanqing,Huang, Yubing
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supporting information
p. 238 - 241
(2013/03/13)
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- Mild conversion of propargylic alcohols to α,β-unsaturated enones in ionic liquids (ILs); A new 'metal free' life for the Rupe rearrangement
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A mild and selective transition metal free protocol for the conversion of propargylic alcohols to cyclic and acyclic α,β-unsaturated enones via the Rupe rearrangement is reported. The method utilizes the Br?nsted acidic ionic liquid [BMIM-SO3H][OTf] as catalyst and [BMIM][PF 6] as solvent and offers the potential for recycling and reuse of the IL solvent. The feasibility to synthesize bicyclic fused cyclopentenone derivatives via a Rupe → Aldol → Nazarov sequence utilizing this protocol has also been demonstrated.
- Nandi, Ganesh C.,Rathman, Benjamin M.,Laali, Kenneth K.
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supporting information
p. 6258 - 6263
(2013/10/22)
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- Improved synthesis of tertiary propargyl alcohols by the Favorskii reaction of alkyl aryl (hetaryl) ketones with acetylene
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Alkyl aryl (hetaryl) ketones react with acetylene under atmospheric pressure in the superbasic system KOH-EtOH-H2O-DMSO at 10-15 C (2 h) to give the corresponding tertiary propargyl alcohols in up to 91% yield. The procedure requires no large excess of KOH and low-boiling inflammable solvents, produces few wastes, and is safe and convenient on the laboratory scale; there are no limitations for its large-scale application.
- Shmidt,Bidusenko,Protsuk,Mikhaleva,Trofimov
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- Synthesis of allenes via gold-catalyzed intermolecular reaction of propargylic alcohols and aromatic compounds
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Functionalized allenes are efficiently synthesized in moderate to high yield from gold-catalyzed intermolecular reaction of propargylic alcohols and aromatic compounds. The user-friendly process could be conducted under mild reaction conditions with easily accessible starting materials.
- Xu, Cheng-Fu,Xu, Mei,Yang, Liu-Qing,Li, Chuan-Ying
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p. 3010 - 3016
(2012/05/05)
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- Chiral silver phosphate-catalyzed cycloisomeric kinetic resolution of α-allenic alcohols
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A kinetic resolution of α-allenic alcohols is realized through chiral silver phosphate-catalyzed cycloisomerization with high stereoselectivity (selectivity factor up to 189) and tolerance of a variety of functional groups. A mechanistic model is proposed to interpret the origin of the high stereoselectivity and broad substrate scope.
- Wang, Yan,Zheng, Kuan,Hong, Ran
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supporting information; scheme or table
p. 4096 - 4099
(2012/04/10)
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- Gold-catalyzed regioselective hydration of propargyl acetates assisted by a neighboring carbonyl group: Access to α-acyloxy methyl ketones and synthesis of (±)-actinopolymorphol B
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A general atom-economical approach for the synthesis of α-acyloxy methyl ketone is demonstrated through regioselective hydration of a wide range of propargyl acetates. Readily available catalyst comprising of 1% Ph 3PAuCl and 1% AgSbF6 in dioxane-H2O efficiently hydrolyzes the terminal alkynes of the propargyl acetate in the absence of acid promoters at ambient temperature within a short time. Effective regioselective hydration is facilitated by the neighboring carbonyl group as demonstrated through 18O-labeling study. Compatibility of functional moieties and tolerance to various acid-labile protecting groups are observed. The catalytic condition is also suitable to perform hydration of TMS-substituted propargyl acetates, even though it requires prolonged reaction time for completion. Stereointegrity of the propargylic acetate is preserved during the hydration. The robustness of the system is successfully demonstrated through gram scale preparation of the product in nearly quantitative yield. The common α-acyloxy methyl ketone is transformed to 1,2-diol and 1,2-amino alcohol derivatives. Synthesis of actinopolymorphol B is achieved for the first time involving hydration of the propargyl acetate as the key step.
- Ghosh, Nayan,Nayak, Sanatan,Sahoo, Akhila K.
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p. 500 - 511
(2011/04/17)
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- Gold-catalyzed formal [3 + 3] and [4 + 2] cycloaddition reactions of nitrosobenzenes with alkenylgold carbenoids
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We report two new formal cycloaddition reactions between nitrosobenzenes and alkenylgold carbenoids. We obtained quinoline oxides 3 in satisfactory yields from the gold-catalyzed [3 + 3]-cycloadditions between nitrosobenzenes and alkenyldiazo esters 1. For propargyl esters 5, its resulting gold carbenes react with nitrosobenzene to give alkenylimine 8, followed by a [4 + 2]-cycloaddition with nitrosobenzene.
- Pagar, Vinayak Vishnu,Jadhav, Appaso Mahadev,Liu, Rai-Shung
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supporting information; experimental part
p. 20728 - 20731
(2012/02/13)
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- Tandem reaction of propargyl alcohol and N-sulfonylhydrazone: Synthesis of dihydropyrazole and its utility in the preparation of 3,3-diarylacrylonitrile
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An efficient and straightforward strategy for the synthesis of 4-methylene-1-(phenylsulfonyl)-4,5-dihydro-1H-pyrazole from propargyl alcohol and N-sulfonylhydrazone is described. N-Sulfonyl allenamide is postulated to be the key intermediate for this tandem transformation.
- Zhu, Yuanxun,Wen, Shan,Yin, Guangwei,Hong, Deng,Lu, Ping,Wang, Yanguang
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supporting information; experimental part
p. 3553 - 3555
(2011/09/14)
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- Stereoselective One-Pot synthesis of 1-Aminoindanes and 5,6-Fused azacycles using a Gold-Catalyzed Redox-Pinacol-Mannich-Michael cascade
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"Chemical Equation Presented" Just another Mannich Monday: A cascade intramolecular redox-pinacol-Mannich-Michael reaction sequence catalyzed by gold complexes can be used to generate a variety of structures including spirocycles, 1-aminoindanes, and 5,6-fused azabicycles that have a quaternary carbon center. The reaction is characterized by complete atom-economy, high diastereoselectivity, and remarkable efficiency through tandem reactions.
- Yeom, Hyun-Suk,Lee, Youngun,Jeong, Jaewon,So, Eunsoo,Hwang, Soojin,Lee, Ji-Eun,Lee, Shim Sung,Shin, Seunghoon
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supporting information; experimental part
p. 1611 - 1614
(2010/06/15)
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- Hydrolase-catalyzed stereoselective preparation of protected α,α-dialkyl-α-hydroxycarboxylic acids
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The title compounds were prepared by a Passerini multi-component reaction and subjected to enzymatic kinetic resolution using 40 enzymes known to be active towards esters of tertiary alcohols. This identified a protease (P1), a thermophilic esterase (PestE) and an esterase of metagenome origin (esterase 8) as the most active and enantioselective biocatalysts. After further optimization of reaction conditions, two compounds were prepared in preparative scale using esterase 8 yielding (+)-1-(tert-butylamino)-2-methyl-1-oxobutyl-2-yl acetate with 93%ee and (-)-1-(tert-butylamino)-2-trifluoro-methyl-1-oxobutyl-2-yl acetate with 47%ee.
- Kourist, Robert,Nguyen, Giang-Son,Struebing, Dirk,Boettcher, Dominique,Liebeton, Klaus,Naumer, Christian,Eck, Juergen,Bornscheuer, Uwe T.
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p. 1839 - 1843
(2008/12/22)
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- Efficient synthesis of 3-chloromethyl-2(5H)-furanones and 3-chloromethyl- 5,6-dihydropyran-2-ones via the PdCl2-catalyzed chlorocyclocarbonylation of 2,3- or 3,4-allenols
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(Chemical Equation Presented) A mild and efficient methodology involving PdCl2-catalyzed chlorocyclocarbonylation of 2,3- or 3,4-allenols with CuCl2 for the synthesis of 3-chloromethyl-2(5H)-furanones and 3-chloromethyl-5,6-dihydropyran-2-ones was developed. This reaction proceeded in a highly regioselective manner, i.e., the chlorine atom was introduced to the terminal position of the allene moiety while the lactone linkage was formed between the center carbon atom of the allene moiety and the hydroxyl oxygen, which was established by the X-ray single crystal diffraction study of γ-lactone 3p. The highly optically active 3-chloromethyl-2(5H)-furanones could be easily prepared from the readily available optically active 2,3-allenols. A mechanism for this reaction was proposed.
- Cheng, Xin,Jiang, Xuefeng,Yu, Yihua,Ma, Shengming
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scheme or table
p. 8960 - 8965
(2009/04/11)
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- Construction of highly substituted stereodefined dienes by cross-coupling of α-allenic acetates
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The assembly of highly substituted dienes remains a challenge for organic chemistry. This work represents a strategy for the construction of highly substituted 1,3-dienes by means of a Tsuji-Trost cross coupling between α-allenic acetates and organozinc reagents. The reaction is high yielding, and installs a trisubstituted olefin with E/Z selectivities up to 95:5 favoring the (E) product. A cheap, commercially available palladium precatalyst and a ligand are used to control the E/Z selectivity. Furthermore, an interesting reversal in selectivity is noted in which appropriate choice of ligand may be used to control the outcome of the reaction and favor the (Z) product. Thirteen examples are described, highlighting the substrate scope of the reaction. It is hoped that the straight-forward reaction conditions and high selectivity will make this reaction of broad use in natural product chemistry. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Schneekloth Jr., John S.,Pucheault, Mathieu,Crews, Craig M.
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- Asymmetric dihydroxylation of disubstituted allenes
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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)
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- P(RNCH2CH2)3N: Efficient catalysts for transesterifications, acylations, and deacylations
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Extremely strong nonionic superbases of the type P(RNCH2CH2)3N catalyze the transesterification of carboxylic acid esters with high selectivity and yields at 25 °C. These bases also catalyze the deacetylation of alcohols under mild conditions in quantitative yields. Using enol acetates as acylating agents, primary and secondary alcohols are efficiently protected as acetates through the action of these catalysts. Substituents such as epoxide, carbamate, acetal, oxazoline, nitro, and alkynyl functionalities are tolerated under the reaction conditions. N-Protected peptides undergo clean transesterification without significant racemization, making this methodology potentially very useful.
- Ilankumaran, Palanichamy,Verkade
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p. 3086 - 3089
(2007/10/03)
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- Facile preparation of substituted allenic esters via the ortho ester Claisen rearrangement
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Five substituted allenic esters were prepared in good yields through the ortho ester Claisen rearrangement of primary and secondary propargyl alcohols.
- Lai,Anderson
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p. 4087 - 4091
(2007/10/03)
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- Hydrolytic Resolution of Tertiary Acetylenic Acetate Esters With the Lipase from Candida Cylindracea
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The kinetic resolution of a series of tertiary acetylenic acetate esters using the lipase from Candida cylindracea has been explored.Compounds 6c and the trifluoromethyl acetate 6e have been resolved with high enantiomeric enrichment.Several other tertiary acetate esters carrying a CF3 group have been investigated which proved inert to enzymatic hydrolysis.From these results and published data, we are able to propose a predictive model for identifying the preferred enantiomer of secondary and tertiary trifluoromethyl acetate esters for this lipase.
- O'Hagan, David,Zaidi, Naveed A.
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p. 947 - 949
(2007/10/02)
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- Optically active propargyl alcohol derivative and a method for preparation of the same
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An optically active propargyl alcohol derivative of the formula (I) STR1 wherein X=phenyl or thienyl and R=lower alkyl, halogenated methyl, phenyl or substituted phenyl having at least one lower alkyl radical and or halogen atom, is prepared by contacting a racemic modification of l- and d-isomers of the formula (I) with l-brucine in an organic solvent, by separating the resultant deposited diastereomer from a solution containing the resultant other diastereomer in the organic solvent, by decomposing each diastereomer with an aqueous mineral acid solution in the presence of an organic solvent capable of dissolving the corresponding optically active isomer dissociated from the diastereomer and incompatible with water so as to allow the optically active isomer to be dissolved in the water-incompatible organic solvent, and by recovering the optically active isomer from the solution thereof.
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- The reaction of some propargyl alcohols with benzeneselenenyl chloride
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The reaction of benzeneselenenyl chloride with twenty-two propargyl alcohols in methylene chloride solution is reported.Products of both Markownikoff and anti-Markownikoff regiochemistry are formed in an anti stereospecific manner.The regioselectivity or specificity is found to be very dependent upon the nature of the substituents geminal to the alcoholic moiety.In general the presence of bulky substituents geminal to the alcoholic moiety tend to favour formation of the anti-Markownikoff adduct under conditions of kinetic control.The Markownikoff adducts are found to be favoured thermodynamically.
- Garratt, Dennis G.,Beaulieu, Pierre L.,Morisset, Veronique M.
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p. 927 - 934
(2007/10/02)
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- Reactions of palladium(0)-phosphine complexes with terminal α-hydroxyacetylenes
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The reactions of acetylenes with the zerovalent palladium complexes (PPh3)nPd, where n = 3 or 4, and (R3P)2Pd(C2H4), where R3P = (CH3)2PC6H5 or Ph3P, have been studied. It was found that terminal acetylenes react with these complexes to produce the air-stable colorless crystalline complexes trans-(R3P)2Pd(C≡CR)2 in reasonable yield. No complexes could be isolated from reactions with nonterminal acetylenes; rather uncharacterizable "thick black soups" were formed. The complexes have been characterized by elemental analyses and by infrared, Raman, and pmr spectroscopy as well as by chemical reactions. Mechanistic implications are presented and discussed in relation to similar reactions with the analogous zerovalent platinum complexes. The relationships of these reactions to homogeneous catalysis by zerovalent complexes of the nickel triad are presented.
- Nelson, John H.,Verstuyft, Allen W.,Kelly, James D.,Jonassen, Hans B.
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