- Tuning the catalytic performance for the semi-hydrogenation of alkynols by selectively poisoning the active sites of Pd catalysts
-
Semi-hydrogenation of alkynols to alkenols with Pd-based catalysts is of great significance in fine chemical industries. Industrial Lindlar catalysts, employing Pb to modify the Pd nanoparticles for higher selectivity toward alkenols, however, generally suffer from both a severe activity decrease and environment pollution caused by using heavy metal Pb and additives. Therefore, how to overcome the selectivity-activity paradox remains a great challenge in industry. Here, we report a controllable strategy for the synthesis of semi-hydrogenation catalysts, which successfully improves the catalytic performance through selectively poisoning the edge and corner sites of Pd nanoparticles. When the integrity of the crystal face is reserved, both higher activity (~1340 h-1) and selectivity (~95% at 99% conversion) are achieved in the semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) in ethanol, an industrially important intermediate product for the synthesis of vitamin E, without adding any toxic additives. What's more, the yield could exceed 98% at 99% conversion under no solvent and organic adsorbate conditions, which had never been achieved before. This work provides a different perspective to design and develop high performance catalysts for semi-hydrogenation of alkenols or even substituted alkynes.
- Mao, Shanjun,Zhao, Bowen,Wang, Zhe,Gong, Yutong,Lü, Guofeng,Ma, Xiao,Yu, Lili,Wang, Yong
-
p. 4143 - 4151
(2019/08/07)
-
- Structurally diverse glycoconjugated volatile compounds from Oxytropis falcata Bunge
-
A phytochemical investigation on the whole plant of Oxytropis falcata Bunge yielded 16 glycoconjugated compounds with structurally diverse volatile aglycones but similar sugars. Of these, five were previously undescribed compounds with different volatile aglycones but same glucuronic acid (1 → 2) glucosyl moiety, including three octanol glucuronic acid (1 → 2) glucosides (1–3), one acyclic monoterpenoid glucuronic acid (1 → 2) glucoside (4), and one 4-phenyl-butan-2-ol glucuronic acid (1 → 2) glucoside (5), and 11 were biological related known glucoconjugated volatile compounds (6–16) isolated from genus Oxytropis for the first time. The structures of these compounds were determined by extensive spectroscopic analysis of MS, 1D and 2D NMR data. The absolute configurations of aglycones and sugar residues were assigned via enzymatic hydrolysis and subsequently comparison of the specific rotations. This is the first report of such structurally diverse glycoconjugated volatile compounds from O. falcata, which might be regarded as the precursor of free volatile compounds, and presents scientific evidences for better clarifying the volatile compositions of this medicinal plant and genus Oxytropis.
- Wang, Shanshan,Zhang, Xiaojing,Que, Sheng,Liang, Hong,Tu, Pengfei,Zhang, Qingying
-
p. 143 - 147
(2018/07/29)
-
- Metal-organic framework Co(D-cam)1/2(bdc)1/2(tmdpy) for improved enantioseparations on a chiral cyclodextrin stationary phase in gas chromatography
-
Initial efforts to combine a chiral metal-organic framework (MOF), Co(D-Cam)1/2(bdc)1/2(tmdpy) (D-Cam=D-camphoric acid, bdc=1,4-benzenedicarboxylic acid, tmdpy=4,4′-trimethylenedipyridine), with peramylated β-cyclodextrins to investigate whether the use of a MOF can enhance enantioseparations on a cyclodextrin stationary phase are reported. Compared with columns of peramylated β-cyclodextrin incorporated in a MOF containing sodium chloride, the column of peramylated β-cyclodextrin+MOF shows excellent selectivity for the recognition of racemates, and higher resolutions are achieved on the peramylated β-cyclodextrin+MOF stationary phase. Experimental results indicate that the use of Co(D-Cam) 1/2(bdc)1/2(tmdpy) can improve enantioseparations on peramylated β-cyclodextrins. This is the first report that chiral MOFs can improve enantioseparations on a chiral stationary phase for chromatography. Copyright
- Liu, Hong,Xie, Sheng-Ming,Ai, Ping,Zhang, Jun-Hui,Zhang, Mei,Yuan, Li-Ming
-
p. 1103 - 1108
(2014/11/07)
-
- Synthesis and reactions of the optically active selenols derived from monoterpenes Dedicated to Professor Jacek Gawronski on the occasion of his 70th birthday
-
A convenient methodology for the synthesis of optically active selenols, derived from p-menthane, carane, and pinane, is described. The selenols were oxidized with air to give the optically active diselenides, and were also converted into the corresponding allylic selenides via reaction with Z- and E-cinnamyl, geranyl, and neryl chlorides. Oxidation of the allylic selenides with mCPBA gave the optically active alcohols via [2,3]-sigmatropic rearrangement of the in situ generated allylic selenoxides.
- Scianowski, Jacek,Rafalski, Jaroslaw,Banach, Anna,Czaplewska, Justyna,Komoszynska, Anna
-
p. 1089 - 1096
(2013/10/08)
-
- Characterization of a novel esterase isolated from intertidal flat metagenome and its tertiary alcohols synthesis
-
A gene coding for an esterase (EstEH112) was isolated from metagenome originated from Korean intertidal flat sediment. The putative esterase gene encoded a 340 amino acids protein with characteristic residues of lipolytic enzymes such as a conserved pentapeptide (GXSXG), the typical catalytic S-D-H triad, and a GGG(A)X-motif in the oxyanion hole near the active site similar to the hormone sensitive lipase (HSL) family. p-Nitrophenyl butyrate was the best substrate for the enzyme among the other p-nitrophenyl esters investigated. The apparent optimal temperature and pH for EstEH112 was 35°C and at pH 8.0, respectively. EstEH112 efficiently catalyzed the hydrolysis of various large tertiary alcohol esters. These characteristics of EstEH112 make it a potential candidate for application in biocatalysis.
- Oh, Ki-Hoon,Nguyen, Giang-Son,Kim, Eun-Young,Kourist, Robert,Bornscheuer, Uwe,Oh, Tae-Kwang,Yoon, Jung-Hoon
-
experimental part
p. 67 - 73
(2012/09/07)
-
- Enantioselective synthesis of allylboronates bearing a tertiary or quaternary B-substituted stereogenic carbon by NHC-Cu-catalyzed substitution reactions
-
Allylic substitutions that afford α-substituted allylboronates bearing B-substituted tertiary or quaternary carbon stereogenic centers are presented. C-B bond-forming reactions, catalyzed by chiral bidentate Cu-NHC complexes, are performed in the presence of commercially available bis(pinacolato)diboron. Transformations proceed in high yield (up to >98%) and site selectivity (>98% SN2′), and in up to >99:1 enantiomer ratio. Trans- or cis-disubstituted alkenes can be used; alkyl- (linear as well as branched) and aryl-trisubstituted allylic carbonates serve as effective substrates. Allylboronates that bear a quaternary carbon center are air-stable and can be easily purified by silica gel chromatography; in contrast, secondary allylboronates cannot be purified in the same manner and are significantly less stable. Oxidation of the enantiomerically enriched products furnishes secondary or tertiary allylic alcohols, valuable small molecules that cannot be easily obtained in high enantiomeric purity by alternative synthesis or kinetic resolution approaches.
- Guzman-Martinez, Aikomari,Hoveyda, Amir H.
-
supporting information; experimental part
p. 10634 - 10637
(2010/11/05)
-
- An efficient procedure for the 1,3-transposition of allylic alcohols based on lithium naphthalenide induced reductive elimination of epoxy mesylates
-
An efficient protocol for the 1,3-transposition of allylic alcohols has been developed. The method is based on the pretransformation of allylic alcohols into the corresponding epoxy mesylates, followed by the reductive elimination of the resulting epoxy mesylates by using lithium naphthalenide (LN) as a reducing agent. Georg Thieme Verlag Stuttgart.
- Wu, Yen-Ku,Liu, Hsing-Jang,Zhu, Jia-Liang
-
p. 621 - 623
(2008/12/22)
-
- Enzymatic alcoholysis of alkoxymethyl alkanoates: A possible approach for the kinetic resolution of tertiary alcohols
-
The pivaloyloxymethyl and butanoyloxymethyl derivatives of tert-butanol and linalool (1.4) are readily accepted by hydrolases. Linalool derivative 4b is alcoholysed stereoselectively by Candida rugosa lipase (E=9.7).
- Franssen, Maurice C.R.,Goetheer, Earl L.V.,Jongejan, Hugo,De Groot, Aede
-
p. 8345 - 8348
(2007/10/03)
-
- Asymmetric [2,3]sigmatropic rearrangement of optically active allylic selenides
-
Oxidation of an optically active allylic selenide derived from L-proline 1 with m-chloroperbenzoic acid afforded the corresponding chiral allylic alcohol 3 via asymmetric [2,3]sigmatropic rearrangement with fair enantioselectivity (up to 66% e.e.).
- Fujita, Ken-Ichi,Kanakubo, Mitsuhiro,Ushijima, Hirobumi,Oishi, Akihiro,Ikeda, Yoshikazu,Taguchi, Yoichi
-
p. 987 - 988
(2007/10/03)
-
- First synthesis of optically pure selenuranes and stereoselective alkaline hydrolysis. Their application to asymmetric [2,3] sigmatropic rearrangement of allylic selenoxides
-
The first synthesis of optically pure selenuranes 1 has been accomplished by utilizing 2-exo-hydroxy-10 bornyl group as a chiral ligand Complete retention of the configuration has been observed in alkaline hydrolysis of 1 to give selenoxides 2. The structure of 1 and 2 has been fully established by X-ray crystallography. [2,3] Sigmatropic rearrangement of allylic selenoxides 2 gave the corresponding allylic alcohols 3 with up to 88% enantiomeric excess (ee). The [2,3] sigmatropic rearrangement of allylic selenoxides 2 progresses predominantly via an endo transition state.
- Kurose, Noriyuki,Takahashi, Tamiko,Koizumi, Toru
-
p. 12115 - 12129
(2007/10/03)
-
- One-pot transformation of p-toluenesulfonates of 2,3-epoxy alcohols into allylic alcohols
-
A convenient and efficient method for the synthesis of synthetically useful non-racemic allylic alcohols from 4-methylbenzenesulfonates of non- racemic 2,3-epoxy alcohols is described. Satisfactory yields are obtained by treatment of 4-methylbenzenesulfonates of non-racemic 2,3-epoxy alcohols with potassium iodide followed by zinc powder and ammonium chloride in a one-pot manner. The method has been successfully applied to the synthesis of a key building block of C30-C37 botryococcenes.
- Habashita, Hiromu,Kawasaki, Takeshi,Akaji, Masako,Tamamura, Hirokazu,Kimachi, Tetsutaro,Fujii, Nobutaka,Ibuka, Toshiro
-
p. 8307 - 8310
(2007/10/03)
-
- First total synthesis of two new diglycosides, neohancosides A and B, from Cynanchum hancockianum
-
Neohancosides A (1) and B (2) are monoterpene diglycosides isolated from Cynanchum hancockianum, which is a Chinese folk medicine having antitumor activity. First total synthesis of 1 and 2, (3R)-linaloyl and (3R)-8-hydroxylinaloyl 3-O-β-D-xylopyranosyl-(1 → 6)-β-D-glucopyranosides were achieved stereoselectively using fluoride 12b as a glycosyl donor. The asymmetry of C-3 in 1 and 2 was introduced efficiently by separating diasteremers of (3R), (3S)-linaloyl and (3R), (3S)-8-benzoyloxylinaloyl 3-O-2,3,4-tri-O-benzoyl-β-D-glucopyranoside, 19 and 21 and 20 and 22, respectively. Absolute configurations of 1 and 2 were determined by enzymatic degradation of synthetic intermediates 33 and 34.
- Konda, Yaeko,Toida, Tsuneyuki,Kaji, Eisuke,Takeda, Kazuyoshi,Harigaya, Yoshihiro
-
p. 123 - 143
(2007/10/03)
-
- 1,3-Transposition of primary allylic alcohols: Synthesis of optically active secondary and tertiary allylic alcohols
-
The reduction of optically active 2,3-epoxy alcohols, suitably prepared by the Sharpless asymmetric epoxidation of primary allylic alcohols, with the system triphenylphosphine/ iodine/imidozole/2,6-lutidine/water, leads in a single step to optically active secondary and tertiary allylic alcohols.
- Dorta, Rosa L.,Rodriguez, Maria S.,Salazar, Jose A.,Suarez, Ernesto
-
p. 4675 - 4678
(2007/10/03)
-
- First total synthesis of new diglycosides, neohancoside A, and B from Cynanchum hancockianum
-
First total synthesis of monoterpene diglycosides, neohancosides A (1) and B (2) from Cynanchum hancockianum were achieved stereoselectively using fluoride as a glycosyl donor. The absolute configurations of 1 and 2 were determined by enzymatic degradation of synthetic intermediates.
- Konda, Yaeko,Toida, Tsuneyuki,Kaji, Eisuke,Takeda, Kazuyoshi,Harigaya, Yoshihiro
-
p. 4015 - 4018
(2007/10/03)
-
- Simple one-pot transformations of toluene-p-sulfonates of 2,3-epoxy alcohols into allylic alcohols
-
A simple synthetic method for the preparation of scalemic allylic alcohols from toluene-p-sulfonates of scalemic 2,3-epoxy alcohols is reported. Satisfactory yields are obtained by treatment of toluene-p-sulfonates of 2,3-epoxy alcohols with potassium iodide followed by triphenylphosphine and iodine in a one-pot synthesis.
- Fujii, Nobutaka,Habashita, Hiromu,Akaji, Masako,Nakai, Kazuo,Ibuka, Toshiro,Fujiwara, Masahiro,Tamamura, Hirokazu,Yamamoto, Yoshinori
-
p. 865 - 866
(2007/10/03)
-
- Synthesis of - and -Bisferrocenyl> Diselenides and Their Application to Asymmetric Selenoxide Elimination and Sigmatropic Rearrangement
-
Novel optically-active bisferrocenyl> diselenides ( and ), each of which possesses two axial and two central elements of chirality, have been prepared by lithiation of commercially available chiral ferrocenes, followed by reaction with elemental selenium and air oxidation, in 77-80percent isolated yields.The structure of the -bisferrocenyl diselenide has been fully characterized by X-ray crystallography.Six chiral ferrocenyl vinylic selenides and six chiral allylic ferrocenyl selenides have been newly prepared by reaction of the diselenides with the corresponding propiolate derivatives and allylic halides.The oxidation of the vinylic selenides with m-chloroperbenzoic acid in various organic solvents produces axially chiral allenecarboxylic esters via asymmetric selenoxide elimination in 27-59percent chemical yields with high enantioselectivities (up to 89percent ee).Similar treatment of the allylic selenides afforded the corresponding chiral allylic alcohols via asymmetric sigmatropic rearrangement in 28-82percent chemical yields with high enantioselectivities (up to 89percent ee).The observed high enantioselectivities indicate that oxidation proceeds diastereoselectively, that the resultant chiral selenoxides are slow to racemize, and also that selenoxide elimination and sigmatropic rearrangement proceed with little loss of optical activity.
- Nishibayashi, Yoshiaki,Singh, Jai Deo,Fukuzawa, Shin-ichi,Uemura, Sakae
-
p. 4114 - 4120
(2007/10/02)
-
- An extremely mild desulfurization of thiiranes: An efficient transformation from geraniol to (+)- and (-)-linalool
-
Thiirane was transformed to alkene very efficiently at -78°C by triethylborane initiated radical reaction with tributyltin hydride. Enantiomerically pure (+)- and (-)-linalools were derived from geraniol in four steps including the alkene formation reaction.
- Uenishi,Kubo
-
p. 6697 - 6700
(2007/10/02)
-
- A catlaytic tellurium process for the transposition of allylic hydroxyl groups and carbon-carbon double bonds
-
As little as 0.1 molar equivalent of elemental tellurium in combination with excess (up to 3 molar equivalents) reducing agent (HOCH2SO2Na·H2O, NaBH4, or LiEt3BH) effects the telluride-ion mediated transposition of allylic hydroxyl groups and carbon-carbon double bonds that proceeds via the epoxy tosylate. The workup is much more convenient than when a molar equivalent of tellurium is used.
- Kumar, Archana,Dittmer, Donald C.
-
p. 5583 - 5586
(2007/10/02)
-
- A Tellurium Transposition Route to Allylic Alcohols: Overcoming Some Limitations of the Sharpless-Katsuki Asymmetric Epoxidation
-
Good yields of enantiomeric allylic alcohols can be obtained in high enantiomeric excess (ee) by combining Sharpless-Katsuki asymmetric epoxidation process (SAE) with tellurium chemistry.The advantages of the tellurium process are as follows: (1) the 50percent yield limitation on the allylic alcohol in the Sharpless kinetic resolution (SKR) can be overcome; (2) allylic tertiary alcohols which are unsatisfactory substrates in the SKR can be obtained in high optical purity; (3) optically active secondary allylic alcohols with tertiary alkyl substituents (e.g. tert-butyl) at C-1 can be obtained in high ee; (4) optically active sterically congested cis secondary alcohols can be obtained in high ee; and (5) the nuisance of the slow SAE of some vinyl carbinols can be avoided.The key step in the reaction sequence is either a stereospecific 1,3-transposition of double bond and alcohol functionalities or an inversion of the alcohol configuration with concomitant deoxygenation of the epoxide function in epoxy alcohols.Trans secondary allylic alcohols can be converted to cis secondary allylic alcohols by way of erythro epoxy alcohols (glycidols); threo glycidyl derivatives are converted to trans secondary allylic alcohols.These transformations are accomplished by the action of telluride ion, generated in situ from the element, on a glycidyl sulfonate ester.Reduction of elemental Te is conveniently done with rongalite (HOCH2SO2Na) in an aqueous medium.This method is satisfactory when Te2- is required to attack at primary carbon site of a glycidyl sulfonate.In cases where Te2- is required to attack a secondary carbon site, reduction of the tellurium must be done with NaBH4 or LiEt3BH.Elemental tellurium is precipitated during the course of the reactions and can be recovered and reused.
- Dittmer, Donald C.,Discordia, Robert P.,Zhang, Yanzhi,Murphy, Christopher K.,Kumar, Archana,et al.
-
p. 718 - 731
(2007/10/02)
-
- Larger Scale Preparation of Optically-active Allylic Alcohols
-
An efficient and practical synthesis of optically-active allylic alcohols from 2,3-epoxytoluene-p-sulfonates by the in situ formation of the epoxy iodides and their subsequent reduction with zinc-copper couple has been established.Application of this procedure to the larger-scale synthesis of (S)-(+)-but-3-en-2-ol from (2S,3S)-3-methylglycidyl toluene-p-sulfonate has also been investigated.
- Balmer, Ethnie,Germain, Andrew,Jackson, William P.,Lygo, Barry
-
p. 399 - 400
(2007/10/02)
-
- Oxirane Ring-Opening with Alcohol Catalyzed by Organotin Phosphate Condensates. Complete Inversion at Tertiary and Benzylic Centers
-
Regio- and stereospecific ring-opening of chiral oxiranes has been effected by organotin phosphate condensates catalyst.Alcohols attack on the tertiary and benzylic positions exclusively.Despite seemingly acidic character of the catalyst in terms of regioselectivity the chiral centers are completely inverted.The new methodology is applied to synthesis of enantiomerically pure linalool and to conversion of commercially available (R)-styrene oxide into the (S)-counterpart.
- Otera, Junzo,Niibo, Yoshihisa,Nozaki, Hitosi
-
p. 7625 - 7634
(2007/10/02)
-