General asymmetric hydrogenation of alpha-branched aromatic ketones catalyzed by TolBINAP/DMAPEN-ruthenium(II) complex

[reaction: see text] A catalyst system consisting of RuCl2[(S)-tolbinap][(R)-dmapen] and t-C4H9OK in 2-propanol effects asymmetric hydrogenation of arylglyoxal dialkylacetals to give the alpha-hydroxy acetals in up to 98% ee. Hydrogenation of racemic alpha-amidopropiophenones under dynamic kinetic resolution predominantly gives the syn alcohols in up to 99% ee and >98% de, while the reaction of racemic bezoin methyl ether gives the anti alcohols in excellent stereoselectivity.     

梨果及土壤中亚胺唑及其代谢物的气相色谱分析

介绍了杀菌剂亚胺唑及其代谢物ＩＢＣ－０１在梨果实及土壤样品内的提取、净化方法以及气相色谱的分析测定方法。保留时间：亚胺唑为３８．３６ｍｉｎ，ＩＢＣ－０１为１７．０１ｍｉｎ。变异系数：亚胺唑为０．４５％～１５．５３％，ＩＢＣ－０１为３．０３％～９．５２％。回收率：亚胺唑为８８．２８％～９８．５％，ＩＢＣ－０１为８４．９８％～９８．１３％。     

Mechanochemical Copper-Catalyzed Asymmetric Michael-Type Friedel–Crafts Alkylation of Indoles with Arylidene Malonates

A mechanochemical version of the asymmetric Michael-type Friedel–Crafts alkylation of indoles with arylidene malonates was developed. The reaction proceeds under ambient atmosphere using a chiral bis(oxazoline)copper catalyst in a mixer mill. Under these reaction conditions nineteen 3-substituted indole derivatives were synthesized in good to excellent yields (up to 98 %), and with good enantioselectivities (up to 91:9 e.r.) after short milling times.     

Rhodium(II,II) dimer as an efficient catalyst for aziridination of sulfonamides and amidation of steroids

[reaction: see text] Unsaturated sulfonamides underwent direct intramolecular aziridination catalyzed by Rh(2)(OAc)(4) with PhI(OAc)(2) and Al(2)O(3) to give the corresponding aziridine products in excellent yields (up to 98%) and with good to excellent conversions. High turnovers (up to 1375) were achieved. The intermolecular rhodium-catalyzed amidation of cholesteryl acetate with PhI=NTs or PhI(OAc)(2)/NH(2)R as the nitrogen source exhibited both excellent regio- and alpha-selectivity (alpha/beta ratio up to 9:1).     

Organocatalytic diastereo- and enantioselective Michael addition reactions of 5-aryl-1,3-dioxolan-4-ones

5-Aryl-1,3-dioxolan-4-one heterocycles derived from mandelic acid derivatives and hexafluoroacetone have been identified as new and effective pro-nucleophiles in highly diastereo- and enantioselective Michael addition reactions to nitro olefins catalyzed by bifunctional epi-9-amino-9-deoxy cinchona alkaloid derivatives. Diastereoselectivities up to 98% and enantioselectivities up to 89% for a range of nitro olefins and 5-aryl-1,3-dioxolan-4-ones under mild reaction conditions are reported.     

A highly organocatalytic stereoselective double Michael reaction: efficient construction of optically enriched spirocyclic oxindoles

An effective double Michael reaction has been disclosed to access spirocyclic oxindoles in high yields (up to 98%) and excellent enantioselectivities (up to 98% ee).     

Highly diastereoselective allylation and reduction of chiral camphor-derived α-ketoamides

The diastereoselective allylation and reduction of camphor-derived α-ketoamides to give optically enriched α-hydroxyl amides with high to excellent stereoselectivities are described. Allylation was carried out using allyltributylstannane in the presence of a stoichiometric amount of a Lewis acid to afford the desired homoallylic alcohols in relatively high chemical yields (up to 98%) and stereoselectivities (up to 98% de). Diastereoselective reductions were performed with the relatively bulky hydride K-Selectride at −78 °C to give the corresponding α-hydroxy amides in excellent chemical yields (up to 98%) and stereoselectivities (up to 98% de). The absolute configuration of the new stereogenic center of the major diastereomer was established by X-ray crystallographic analysis. Finally, stereochemical induction and the Lewis acid dependent reversal of stereoselectivity is described.     

Proline-based reduced dipeptides as recyclable and highly enantioselective organocatalysts for asymmetric Michael addition

A series of novel proline-based reduced dipeptides was developed and evaluated for a direct Michael addition of ketones and aldehydes to nitroalkenes. Excellent yields (up to 95%), diastereoselectivities (up to 98% dr) and enantioselectivities (up to 98% ee) were achieved in the presence of 5 mol% catalyst without any additional additives at room temperature.     

硅胶负载H6PMo9V3O40催化合成5-硝基水杨醛

采用硅胶负载Keggin型H6PMo9V3O40催化水杨醛与硝酸反应合成5-硝基水杨醛,考察了催化剂负载量、反应时间、反应温度、催化剂用量、硝酸用量和溶剂对反应的影响及催化剂的重复使用性能。实验结果表明,m(水杨醛)∶m(质量分数65%硝酸)∶m(负载量20%H6PMo9V3O40/SiO2)=2.44∶3.00∶3.00,用石油醚作为溶剂,45℃反应2.5 h,水杨醛的转化率为98%,5-硝基水杨醛的选择性为96.8%。催化剂回收容易,重复使用5次后,活性基本不变。     

The dienolate aldol reaction of (E)-N-crotonoyl C(4)-isopropyl SuperQuat: asymmetric synthesis of α-vinyl-β-hydroxycarboxylic acid derivatives and conversion to α-ethylidene-β-hydroxyesters (β-substituted Baylis-Hillman products)

The synthesis of α-vinyl-β-hydroxyesters and α-ethylidene-β-hydroxyesters (β-substituted Baylis-Hillman products) via the dienolate aldol reaction of (E)-N-crotonoyl C(4)-isopropyl SuperQuat is described. High levels of syn-diastereoselectivity (up to >98% de) are observed for the dienolate aldol reaction with boron enolates, generated either directly with Bu₂BOTf or by transmetalation of the potassium enolate with B-bromocatecholborane. Cleavage of the resultant syn-aldol products from the auxiliary gives α-vinyl-β-hydroxyesters in >98% de and >98% ee. Subsequent isomerisation of the double bond into conjugation provides α-ethylidene-β-hydroxyesters (β-substituted Baylis-Hillman products) in high diastereo- and enantiopurity (≥91:9 [(E):(Z)] and >98% ee).     

Improved method for the determination of 4'-epidoxorubicin and seven metabolites in plasma by high-performance liquid chromatography

4'-Epidoxorubicin, its seven metabolites and doxorubicin, as internal standard, were efficiently extracted from plasma using C18 Sep-Pak cartridges. The recoveries ranged from 58% for doxorubicin aglycone up to 98% for 4'-epidoxorubicin glucuronide. The anthracyclines were separated by reversed-phase high-performance liquid chromatography within 9 min and analysed by fluorescence. The assay was sensitive to 3 X 10(-10) M for the glucuronides up to 12 X 10(-10) M for 7-deoxydoxorubicin aglycone. The peak-height ratio of the fluorescence intensities of the anthracyclines versus doxorubicin showed a linear correlation with the concentration from the detection limit up to 2.5 X 10(-7) M (correlation coefficient r2 greater than 0.99). Within-day and between-day precision of the assay were in the ranges 2-14% (n = 6) and 2-11% (n = 6), respectively.     

Diastereo- and enantioselective aldol reaction of granatanone (pseudopelletierine)

Granatanone (granatan-3-one, 9-methyl-9-azabicyclo[3.3.1]nonan-3-one, pseudopelletierine or pseudopelletrierin) undergoes deprotonation with lithium amides giving a lithium enolate, which reacts with aldehydes diastereoselectively giving exclusively exo isomers and anti/syn selectivity up to 98:2. Granatanone can be enantioselectively lithiated by chiral lithium amides and the resulting non-racemic enolate can be reacted with aldehydes giving aldols with enantiomeric excess up to 93% (99% ee after recrystallization). The absolute and relative configuration of the aldol products was determined by NMR spectroscopy and X-ray analysis.Granatanone; aldol reaction; asymmetric synthesis; enantioselective deprotonation; chiral lithium amide.     

syn-selective direct catalytic asymmetric Mannich-type reactions of hydroxyketones using Y{N(SiMe3)2}3/linked-BINOL complexes

[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield).     

Synthesis of C1-symmetric chiral secondary diamines and their applications in the asymmetric copper(II)-catalyzed Henry (nitroaldol) reactions

A small library of C(1)-symmetric chiral diamines (L1-L9) was constructed via condensing exo-(-)-bornylamine or (+)-(1S,2S,5R)-menthylamine with various Cbz-protected amino acids. Among them, ligand L1/CuCl(2)·2H(2)O complex (2.5 mol %) shows outstanding catalytic efficiency for Henry reaction between a variety of aldehydes and nitroalkanes to afford the expected products in high yields (up to 98%) with excellent enantioselectivities (up to 99%) and moderate to good diastereoselectivities (up to 90:10). This process is air- and moisture tolerant and has been applied to the synthesis of (S)-2-amino-1-(3,4-dimethoxyphenyl)ethanol (9), a key intermediate for (S)-epinephrine and (S)-norepinephrine. On the basis of HRMS and X-ray diffraction analysis of the L1/CuCl(2) complex, a transition-state model was proposed to explain the origin of asymmetric induction. The low catalyst loading, excellent yields and enantioselectivities, inexpensive copper salt, and mild reaction conditions make our catalytic system to be practically useful.     

A highly enantioselective Diels-Alder reaction of 1,2-dihydropyridine using a simple β-amino alcohol organocatalyst for a practical synthetic methodology of oseltamivir intermediate

An easily prepared chiral amino alcohol catalyst was found to provide an efficient synthetic intermediate of oseltamivir with excellent chemical yield and enantioselectivity (up to 98% yield and up to 98% ee) in enantioselective Diels-Alder reactions of 1,2-dihydropylidines with acroleins.     

Asymmetric Michael addition of α-substituted isocyanoacetates with maleimides catalyzed by chiral tertiary amine thiourea

A highly diastereoselective and enantioselective Michael addition of α-substituted isocyanoacetates with maleimides catalyzed by bifunctional tertiary amine thioureas has been developed. Various chiral succinimide derivatives bearing adjacent quaternary and tertiary stereocenters were prepared in excellent yields (up to 98%), diastereoselectivities (up to 99:1), and enantioselectivities (up to 98% ee). The synthetic utility of chiral succinimide derivatives is also demonstrated in the preparation of h5-HT(1d) receptor agonist motifs.     

Catalytic, highly enantio- and diastereoselective pinacol coupling reaction with a new tethered bis(8-quinolinolato) ligand

A new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is developed. Its chromium complex, TBOxCrCl (3 mol %), effectively catalyzes the pinacol coupling reaction of aromatic aldehydes at room temperature with high yield (up to 94%), high diastereoselectivity (up to dl:meso = 98:2), and high enantioselectivity (up to 98%). The scope of the present method turns out not to be limited to aromatic aldehyde derivatives, as cyclohexanecarboxaldehyde undergoes pinacolization as well (44% yield, dl:meso = 93:7, 84% ee). The method provides an efficient access to enantioenriched 1,2-diols.     

Novel prolinamide–ureas as organocatalysts for the asymmetric aldol reaction

Among the various versions of the aldol reaction, the enantioselective reaction between cyclic ketones and aldehydes constitutes a typical reaction model for the evaluation of novel organocatalysts. A multifunctional organocatalyst consisting of a prolinamide moiety, a gem diamine unit and a urea group was successfully employed in this asymmetric transformation. The products of the reaction between various ketones and aldehydes were obtained in high yields (up to 98%) with excellent diastereo- (up to >98:2 dr) and enantioselectivities (up to 99% ee).     

Biocompatible SuFEx Click Chemistry: Thionyl Tetrafluoride (SOF4)‐Derived Connective Hubs for Bioconjugation to DNA and Proteins

We report here the development of a suite of biocompatible SuFEx transformations from the SOF₄‐derived iminosulfur oxydifluoride hub in aqueous buffer conditions. These biocompatible SuFEx reactions of iminosulfur oxydifluorides (R‐N=SOF₂) with primary amines give sulfamides (8 examples, up to 98 %), while the reaction with secondary amines furnish sulfuramidimidoyl fluoride products (8 examples, up to 97 %). Likewise, under mild buffered conditions, phenols react with the iminosulfur oxydifluorides (Ar‐N=SOF₂) to produce sulfurofluoridoimidates (13 examples, up to 99 %), which can themselves be further modified by nucleophiles. These transformations open the potential for asymmetric and trisubstituted linkages projecting from the sulfur(VI) center, including versatile S?N and S?O connectivity (9 examples, up to 94 %). Finally, the SuFEx bioconjugation of iminosulfur oxydifluorides to amine‐tagged single‐stranded DNA and to BSA protein demonstrate the potential of SOF₄‐derived SuFEx click chemistry in biological applications.     

New chiral ferrocenyl P,S-ligands for highly diastereo-/enantioselective catalytic [3 + 2] cycloaddition of azomethine ylides with cyclic and acyclic enones

A new family of chiral ferrocenyl P,S-ligands has been developed and successfully applied in a highly endo-selective catalytic asymmetric cycloaddition of azomethine ylides with various enones, including cyclic and acyclic α-enones. For cyclic α-enones, a [Cu(CH(3)CN)(4)]ClO(4)/(R(c),S(Fc))-2f complex catalyzed the cycloaddition to give the sole endo-cycloadducts in perfect enantioselectivities (normally 99% ee), while an AgOAc/(R(c),S(Fc))-2f catalytic system exhibited good endo/exo selectivities (endo/exo = 91/9 to 96/4) and high enantiocontrol (up to 98% ee) for acyclic α-enones.