- Rhodium-Catalyzed Parallel Kinetic Resolution of Racemic Internal Allenes Towards Enantiopure Allylic 1,3-Diketones
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A rare case of a parallel kinetic resolution of racemic 1,3-disubstituted allenes by means of a rhodium-catalyzed addition to 1,3-diketones furnishing enantiopure allylic 1,3-diketones is described. Mechanistic experiments demonstrate that the different allene enantiomers react in parallel to either the diastereomeric E- or Z-allylic 1,3-diketones with the same absolute configuration of the newly formed stereogenic center. A broad substrate scope demonstrates the synthetic utility of this new method.
- Hilpert, Lukas J.,Breit, Bernhard
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supporting information
p. 9939 - 9943
(2019/06/24)
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- 1,1-Diphosphines and divinylphosphines via base catalyzed hydrophosphination
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A catalytic hydrophosphination route to 1,1-diphosphines is yet to be reported: these narrow bite angle pro-ligands have been used to great effect as ligands in homogeneous catalysis. We herein demonstrate that terminal alkynes readily undergo double hydrophosphination with HPPh2 and catalytic potassium hexamethyldisilazane (KHMDS) to generate 1,1-diphosphines. A change to H2PPh leads to the formation of P,P-divinyl phosphines.
- Coles,Mahon,Webster
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p. 10443 - 10446
(2018/09/21)
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- Diversification of ortho-Fused Cycloocta-2,5-dien-1-one Cores and Eight- to Six-Ring Conversion by σ Bond C?C Cleavage
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Sequential treatment of 2-C6H4Br(CHO) with LiC≡CR1(R1=SiMe3, tBu), nBuLi, CuBr?SMe2and HC≡CCHClR2[R2=Ph, 4-CF3Ph, 3-CNPh, 4-(MeO2C)Ph] at ?50 °C leads to formation of an intermediate carbanion (Z)-1,2-C6H4{CA(=O)C≡CBR1}{CH=CH(CH?)R2} (4). Low temperatures (?50 °C) favour attack at CBleading to kinetic formation of 6,8-bicycles containing non-classical C-carbanion enolates (5). Higher temperatures (?10 °C to ambient) and electron-deficient R2favour retro σ-bond C?C cleavage regenerating 4, which subsequently closes on CAproviding 6,6-bicyclic alkoxides (6). Computational modelling (CBS-QB3) indicated that both pathways are viable and of similar energies. Reaction of 6 with H+gave 1,2-dihydronaphthalen-1-ols, or under dehydrating conditions, 2-aryl-1-alkynylnaphthlenes. Enolates 5 react in situ with: H2O, D2O, I2, allylbromide, S2Me2, CO2and lead to the expected C-E derivatives (E=H, D, I, allyl, SMe, CO2H) in 49–64 % yield directly from intermediate 5. The parents (E=H; R1=SiMe3, tBu; R2=Ph) are versatile starting materials for NaBH4and Grignard C=O additions, desilylation (when R1=SiMe) and oxime formation. The latter allows formation of 6,9-bicyclics via Beckmann rearrangement. The 6,8-ring iodides are suitable Suzuki precursors for Pd-catalysed C?C coupling (81–87 %), whereas the carboxylic acids readily form amides under T3P conditions (71–95 %).
- Eccleshare, Lee,Lozada-Rodríguez, Leticia,Cooper, Phillippa,Burroughs, Laurence,Ritchie, John,Lewis, William,Woodward, Simon
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supporting information
p. 12542 - 12547
(2016/08/24)
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- Styrene as 4π-Component in Zn(II)-Catalyzed Intermolecular Diels-Alder/Ene Tandem Reaction
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A mild Zn-catalyzed intermolecular Diels-Alder/ene tandem reaction with styrene as a 4π-component is reported. A variety of dihydronaphthalene products could be prepared in moderate to good yields. Moreover, a combination of DFT calculations and experiments was performed to further understand the mechanism of this unique tandem reaction.
- Zheng, Min,Wu, Feng,Chen, Kai,Zhu, Shifa
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supporting information
p. 3554 - 3557
(2016/08/16)
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- Aniline-terephthalaldehyde resin p-toluenesulfonic acid (ATRT) salt as efficient mild polymeric solid acid catalyst
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Aniline-terephthalaldehyde resin p-toluenesulfonic acid (ATRT) salt was easily prepared by the reaction of aniline with 1.25 equiv of terephthalaldehyde in the presence of 1.0 equiv of p-toluenesulfonic acid at 75 C for 24 h in EtOH. ATRT efficiently catalyzed the tetrahydropyranylation of alcohols and deprotection of tetrahydropyranyl (THP), triethylsilyl (TES), and tert-butyldimethylsilyl (TBDMS) ethers. Deprotection of dodecyl THP ether and dodecyl TBDMS ether catalyzed by ATRT proceeded faster than those by pyridinium p-toluenesulfonate (PPTS). ATRT was reused without significant loss of activities.
- Tanemura, Kiyoshi,Suzuki, Tsuneo
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supporting information
p. 6740 - 6743
(2013/11/19)
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- Facile access to 2,5-disubstituted-4-chloromethyl-3-iodofuran derivatives via ICl-mediated cyclization of 1-alkyl-2-alkynylallylic alcohols
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Substituted furans are conveniently synthesized from acyclic secondary 1-alkyl-2-alkynylallylic alcohol precursors via an ICl-promoted cyclization reaction. The furans generated by this method incorporate both iodine and chlorine atoms which may be useful for further elaborations via many known methods. The methodology is suitable for generating a wide array of furan products which can serve as useful building blocks for the synthesis of various biologically active molecules.
- Thongsornkleeb, Charnsak,Rabten, Wangchuk,Ruchirawat, Somsak,Bunrit, Anon,Tummatorn, Jumreang
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p. 6615 - 6619,5
(2012/12/11)
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- Facile access to 2,5-disubstituted-4-chloromethyl-3-iodofuran derivatives via ICl-mediated cyclization of 1-alkyl-2-alkynylallylic alcohols
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Substituted furans are conveniently synthesized from acyclic secondary 1-alkyl-2-alkynylallylic alcohol precursors via an ICl-promoted cyclization reaction. The furans generated by this method incorporate both iodine and chlorine atoms which may be useful for further elaborations via many known methods. The methodology is suitable for generating a wide array of furan products which can serve as useful building blocks for the synthesis of various biologically active molecules.
- Thongsornkleeb, Charnsak,Rabten, Wangchuk,Bunrit, Anon,Tummatorn, Jumreang,Ruchirawat, Somsak
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p. 6615 - 6619
(2013/01/15)
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- Enantioselective copper-catalysed propargylic substitution: Synthetic scope study and application in formal total syntheses of (+)-anisomycin and (-)-cytoxazone
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A copper catalyst with a chiral pyridine-2,6-bisoxazoline (pybox) ligand was used to convert a variety of propargylic esters with different side chains (R=Ar, Bn, alkyl) into their amine counterparts in very high yields and with good enantioselectivities (up to 90% enantiomeric excess (ee)). Different amine nucleophiles were applied in the reactions and the highest enantioselectivities were obtained for aniline and its analogues. Interestingly, some carbon nucleophiles could also be used and with indoles excellent ee values were obtained (up to 98% ee). The versatility of the propargylic amines obtained was demonstrated by their further elaboration to formal total syntheses of the antibiotic (+)-anisomycin and the cytokine modulator (-)-cytoxazone. Copyright
- Detz, Remko J.,Abiri, Zohar,Le Griel, Remi,Hiemstra, Henk,Van Maarseveen, Jan H.
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experimental part
p. 5921 - 5930
(2011/06/26)
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- Three-component reaction for the C2-functionalization of 1-substituted imidazoles with acetylenic ketones and isocyanates
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An efficient method for the direct C2-amidation of 1-substituted imidazoles with acetylenic ketones and isocyanates is reported. This three-component procedure has the advantages of catalyst-free, operational simplicity, mild reaction conditions, and good to excellent yields.
- Shen, Yang,Cai, Shuying,He, Chi,Lin, Xufeng,Lu, Ping,Wang, Yanguang
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supporting information; experimental part
p. 8338 - 8342
(2011/11/12)
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- Gold-catalyzed ethynylation of arenes
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(Figure Presented) A novel gold-catalyzed ethynylation of aromatic rings with electron-deficient alkynes via gold catalyzed C-H activation of both C sp-H and Csp2-H bonds has been developed. This transformation provides aromatic propiolates difficult to prepare by other methods, highlighting the synthetic potential of gold chemistry.
- De Haro, Teresa,Nevado, Cristina
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experimental part
p. 1512 - 1513
(2010/04/04)
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- A mild and efficient cleavage of tert-butyldimethylsilyl (TBS) and tetrahydropyranyl (THP) ethers using a catalytic amount of TBPA+ {radical dot} Sb Cl6-
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A mild and efficient method for the deprotection of the TBS and THP ethers is described. A wide variety of TBS ethers as well as THP ethers can be easily deprotected to the corresponding parent hydroxyl compounds by employing a catalytic amount of tris(4-bromophenyl)aminium hexachloroantimonate (TBPA+ {radical dot} Sb Cl6-) in methanol at room temperature in good yield.
- Xu, Yanfen,Tang, Shouchu,Han, Junjie,She, Xuegong,Pan, Xinfu
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p. 3634 - 3637
(2008/09/19)
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- Enantioselective copper-catalyzed propargylic amination
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(Chemical Equation Presented) A proper copper catalyst with a chiral pyridine-2,6-bisoxazoline (pybox) ligand was used to convert a variety of propargylic acetates with aromatic side chains (R = Ar) into their amine counterparts in high yield and with good selectivity (up to 88% ee). The resulting chiral propargylic amines can be elaborated further into P,N ligands (see scheme; DIPEA = diisopropylethylamine).
- Detz, Remko J.,Delville, Marielle M. E.,Hiemstra, Henk,Van Maarseveen, Jan H.
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p. 3777 - 3780
(2008/12/23)
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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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- Studies on the Cu(I)-catalyzed regioselective anti-carbometallation of secondary terminal propargylic alcohols
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A highly regioselective Cu(I)-catalyzed anti-carbometallation of secondary terminal propargylic alcohols with 1° alkyl or aryl Grignard reagents affording 2-substituted allylic alcohols was developed. By using this method, optically active allylic alcohols can be prepared from the optically active propargylic alcohols without obvious loss of the enantiopurity. The cyclic organometallic intermediate formed may undergo an iodination or a Pd(0)-catalyzed coupling reaction to afford stereo-defined allylic alcohols.
- Lu, Zhan,Ma, Shengming
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p. 2655 - 2660
(2007/10/03)
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- Palladium-catalyzed silastannation of secondary propargylic alcohols and their derivatives
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A series of terminal propargylic alcohols and their derivatives were subjected to Pd-catalyzed silastannation. In all reactions, complete regio- and stereoselectivities were observed with the tributyltin moiety exclusively adding to the internal carbon of the triple bond in a cis fashion, including the first example of a diyne bis-silastannation. Silastannation reaction products could sequentially be protiodesilylated or iododestannylated, thus providing synthetic routes to 1,1-gem-disubstituted alkenylstannanes and iodides, respectively.
- Nielsen, Thomas E.,Le Quement, Sebastian Le,Tanner, David
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p. 1381 - 1390
(2007/10/03)
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- Efficient tetrahydropyranylation of alcohols and detetrahydropyranylation reactions in the presence of catalytic amount of trichloroisocyanuric acid (TCCA) as a safe, cheap industrial chemical
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Preparation and cleavage of THP ethers of different hydroxy functional groups are easily and efficiently performed in the presence of trichloroisocyanuric acid (TCCA) in the absence of solvent with high yields.
- Firouzabadi, Habib,Iranpoor, Nasser,Hazarkhani, Hassan
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p. 3623 - 3630
(2007/10/03)
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- An efficient and highly selective deprotecting method for β-(trimethylsilyl)ethoxymethyl ethers
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A series of β-(trimethylsilyl)ethoxymethyl ethers were hydrolyzed to their corresponding alcohols in high yields by using a catalytic amount of CBr4 (15%) in MeOH under refluxing reaction conditions. The chemoselective deprotection between trialkylsilyl and β-(trimethylsilyl)-ethoxymethyl-protected alcohols can be achieved by using an alcohol with steric hindrance such as iPrOH. The selectivity also can be achieved in the CBr4/MeOH reaction mixture under ultrasonic reaction conditions.
- Chen, Ming-Yi,Lee, Adam Shih-Yuan
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p. 1384 - 1387
(2007/10/03)
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- Enantioselective synthesis of both enantiomers of various propargylic alcohols by use of two oxidoreductases
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The oxidoreductases Lactobacillus brevis alcohol dehydrogenase (LBADH) and Candida parapsilosis carbonyl reductase (CPCR) are suitable catalysts for the reduction of ketones to afford enantiopure sec. alcohols. A broad variety of alkynones (1, 3, and 5) are accepted as substrates and the corresponding propargylic alcohols (2, 4, and 6) are obtained in good yield and excellent enantiomeric excess. By changing the steric demand of the substituents the ee values can be adjusted and even the configurations of the products can be altered.
- Schubert, Thomas,Hummel, Werner,Kula, Maria-Regina,Mueller, Michael
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p. 4181 - 4187
(2007/10/03)
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- A simple and highly efficient deprotecting method for methoxymethyl and methoxyethoxymethyl ethers and methoxyethoxymethyl esters
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A series of methoxyethoxymethyl (MEM)- and methoxymethyl (MOM)-ethers and MEM-esters were hydrolyzed to their corresponding alcohols and carboxylic acids by a catalytic amount of CBr4 (10%) in iPrOH under refluxing reaction condition. The chemoselective hydrolysis between R3Si- and MEM-protected alcohols can be achieved by using different steric bulkness solvents such as MeOH or iPrOH.
- Shih-Yuan Lee, Adam,Hu, Yi-Jung,Chu, Shu-Fang
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p. 2121 - 2126
(2007/10/03)
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- A simple and efficient hydrolyzing method for tetrahydropyranyl ethers
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A series of tetrahydropyranyl ethers are hydrolyzed to the corresponding alcohols in a CBr4/CH3OH (5%/5mL) reaction system under refluxing. This method also enables to deprotect other functionalities such as acetals and ketals.
- Lee,Su,Liao
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p. 1323 - 1326
(2007/10/03)
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- A novel, highly efficient and selective desilylating method for trialkylsilyl ethers
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A series of tert-butyldimethylsilyl, tert-butyldiphenylsilyl and triisopropylsilyl ethers are hydrolyzed to theirs corresponding alcohols in CBr4 / CH3OH (0.1 eq. / 10mL) reaction system under refluxing condition. The chemoselectivity can be achieved between primary and secondary triisopropylsilyl ethers when more hindered 2-propanol is used instead of methanol.
- Lee, Adam Shih-Yuan,Yeh, Hsiu-Chih,Shie, Jiun-Jie
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p. 5249 - 5252
(2007/10/03)
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- Oxygenation of alkynes to α,β-acetylenic ketones with dioxygen catalyzed by N-hydroxyphthalimide combined with a transition metal
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Alkynes were successfully converted into α,β-acetylenic carbonyl compounds through radical-catalyzed aerobic oxidation using N-hydroxyphthalimide (NHPI) combined with a transion metal under mild conditions.
- Sakaguchi, Satoshi,Takase, Tomoyuki,Iwahama, Takahiro,Ishii, Yasutaka
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p. 2037 - 2038
(2007/10/03)
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- Deprotection of Acetals and Silyl Ethers Using Some ?-Acceptors
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Hydrolysis of dodecanol dimethyl acetal and dodecyl silyl ethers in MeCN-H2O was examined using a catalytic silyl amount of ?-acceptors such as 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF4), and chloranil (CA).Cleavage of dodecyl triethylsilyl ether with TCNQ and CA was caused by room light.By application of DDQ-catalyzed deprotection of acetals to hydrolysis of tetrahydropyranyl ethers, the corresponding alcohols were obtained in quantitative yields.
- Tanemura, Kiyoshi,Suzuki, Tsuneo,Horaguchi, Takaaki
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p. 290 - 292
(2007/10/02)
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- Alkyliron and Alkylcobalt Reagents, IV.- High Superiority of Me4CoLi2 and Me4FeLi2 in Comparison to Me2CuLi and Me4MnLi2 in Cross Coupling Reactions with Vinyl Bromides
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The complexes Me4MLi2 (M = Co, Fe, Mn) and Me2CuLi (prepared in situ, but well-known in isolated form) were treated with a series of vinyl bromides.In nearly all cases Me4CoLi2 and Me4FeLi2 proved to by far the best methylating reagents (high yields, reaction at -78 deg C, short reaction time, no excess of the reagent necessary.These reagents will tolerate a hydroxy or cyano group in the substrate, whereas the classical reagent for methylation of vinyl bromides, Me2CuLi, is strongly inhibited by these groups.With the methylation of hydroxyvinyl bromides a new method was found for the synthesis of allyl alcohols. Key Words: Organocobalt complexes / Organoiron complexes
- Kauffmann, Thomas,Stach, Dirk
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p. 913 - 922
(2007/10/02)
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- Novel 6-alkyl and 6.8-dialkylbicyclo(4.2.0)octane derivatives
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Compounds useful in treating or preventing gastrointestinal ulcers and in treating cardiovascular disorders such as thrombosis, hypertension and atherosclerosis are depicted in formulas (1), (2) and (3): STR1 wherein: A is --C C--, trans --HC=CH--, trans --CH=CHCH2 -- or --CH2 CH2 --; X is lower alkyl of 1-6 carbon atoms; Y is hydrogen, exo-(lower alkyl) or endo-(lower alkyl); n is an integer from 2-4; R1 is --CH2 OH, --CHO, --CO2 R or --CO2 H, and the olefin formed by the R1 (CH2)n CH= moiety is either (E) or (Z); R2 is hydrogen or methyl, or optionally --CH=CH2 when A is trans --CH=CHCH2 --; and R3 is linear or branched alkyl, alkenyl or alkynyl having 5-10 carbon atoms, STR2 --(CH2)m -phenyl or CH2 O-phenyl; in which each phenyl may be optionally substituted with lower alkyl, lower alkoxy, trifluoromethyl, or halogen. in which: a is an integer of 0, 1 or 2; b is an integer of 3-7; m is an integer of 0, 1 or 2; and R is STR3 wherein X' is STR4 in which each R4 is independently hydrogen or lower alkyl having 1-6 carbon atoms, or a pharmaceutically acceptable, non-toxic salt or ester thereof.
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- Novel substituted (4.2.0)bicyclooctane derivatives with valuable therapeutic properties
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Compounds useful in treating cardiovascular disorders such as thrombosis, hypertension and atherosclerosis are depicted in formulas (1), (2) and (3): STR1 wherein: A is --C C--, trans --HC=CH--, --CH2 CH2 -- or --CH=CHCH2 --; X is lower alkoxy, hydroxy, or (2,2,2)-trifluoroethoxy; Y is hydrogen, exo-(lower alkyl) or endo-(lower alkyl); is an integer of 2-4; R1 is --CH2 OH, --CHO, --CO2 R or --CO2 H, and the olefin formed by the R1 (CH2)n CH= moiety is either (E) or (Z); R2 is hydrogen or methyl, or optionally --CH=CH2 when A is --CH=CHCH2 --; and R3 is linear or branched alkyl, alkenyl or alkynyl having 5-10 carbon atoms, STR2 --(CH2)m -phenyl or CH2 O-phenyl; in which each phenyl may be optionally substituted with lower alkyl, lower alkoxy, trifluoromethyl, or halogen; in which: a is an integer of 0, 1 or 2; b is an integer of 3-7; m is an integer of 0, 1 or 2; and R is STR3 wherein x is STR4 in which each R4 is independently hydrogen or lower alkyl having 1-6 carbon atoms, and the pharmaceutically acceptable, non-toxic salts and esters thereof.
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- Novel [4,2,0]bicyclooctane derivatives with valuable therapeutic properties
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Compounds useful in treating cardiovascular disorders such as thrombosis, hypertension, and atherosclerosis are compounds depicted in formulas (1), (2), and (3): STR1 wherein: n is 2 or 3; R1 is CH2 OH, CHO, CO2 R or CO2 H; R2 is hydrogen or methyl; and R3 is linear or branched alkyl having 5-10 carbon atoms, STR2 optionally substituted with lower alkyl, lower alkoxy, trifluoromethyl, or halogen, in which a is 0, 1 or 2; b is 3-7; m is 1 or 2; and R is STR3 in which each R4 is independently hydrogen or lower alkyl having 1-6 carbon atoms, and the pharmaceutically acceptable, non-toxic salts and esters thereof.
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- ASYMMETRIC SYNTHESIS BASED ON CHIRAL DIAMINES HAVING PYRROLIDINE RING
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Various highly stereoselective asymmetric reactions based on chiral diamines having pyrrolidine ring are described.Some of these reactions have been successfully applied to the syntheses of natural products.
- Mukaiyama, Teruaki
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p. 4111 - 4119
(2007/10/02)
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- Total Synthesis of Prostaglandin-F2α involving Stereocontrolled and Photo-induced Reactions of Bicycloheptanones
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A short total synthesis of prostaglandin-F2α from cyclopentadiene is described.Acetalisation of bicyclohept-2-en-6-one (1) followed by formation of a singal bromohydrin gave on treatment with base the epoxyacetal (4).Reaction of (4) with the appropriate organocuprate reagent introduced both the 12β side-chain and 11α-hydroxy-group of the embryonic prostaglandin.The fused cyclobutane ring is important as it controls both the stereoselectivity of epoxide formation and the regioselectivity of the subsequent ring-opening reaction.Furthermore, the unusual photochemical behaviour of cyclobutanones was exploited in this synthesis.Irradiation of the bicycloheptan-6-one (9) in aqueous solution and subsequent Wittig olefination afforded prostaglandin-F2α.Baeyer-Villiger oxidation of the same ketone (9) furnished the lactone (16), a known precursor of prostaglandin-E.
- Howard, Colin C.,Newton, Roger F.,Reynolds, Derek P.,Wardsworth, Alan H.,Kelly, David R.,Roberts, Stanley M.
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p. 852 - 857
(2007/10/02)
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