Total synthesis of (+)-laurallene

The stereoselective total synthesis of (+)-laurallene is described. The required key oxocene skeleton possessing trans-orientated alkyl substituents at the α,α′-positions was stereoselectively constructed via the cyclization of the corresponding hydroxy epoxide promoted by Eu(fod)₃.     

Sc(OTf)3-catalyzed intramolecular aza-Prins cyclization for the synthesis of heterobicycles

The coupling of (E)- and (Z)-hex-3-ene-1,6-ditosylamide with various aldehydes in the presence of 10 mol % Sc(OTf)₃ gave the corresponding trans- and cis-fused 1,5-ditosyl-octahydro-1H-pyrrolo[3,2-c]pyridines, respectively, in good yields via intramolecular aza-Prins cyclization, whereas the coupling of (E)- and (Z)-N-(6-hydroxyhex-3-enyl)-4-methylbenzenesulfonamide afforded the corresponding trans- and cis-fused octahydro-1-tosylpyrano[4,3-b]pyrroles derivatives, respectively, via intramolecular Prins-cyclization.     

Mass spectrometry of the paramagnetic nmr shift reagents Eu(fod)3 and Yb(fod)3 and their adducts with propylamine

By means of electron impact mass spectrometry, the occurrence of dimeric (or higher) associates of the lanthanide shift reagents Eu(fod)₃ and Yb(fod)₃ has been demonstrated. Also, the occurrence of 1:1 and 1:2 adducts of Ln(fod)₃ with propylamine was shown.     

Catalysis of homo diels-alder reactions by Yb(fod)3

The use of Yb(fod)₃ to catalyze Diels-Alder reactions of acrolein with sensitive dienes in nearly stoichiometric ratio and with high stereoselectivity is described.     

Electronic tuning cyclization of aryl-1,4-enediones: AlCl3-mediated Nazarov-type cyclization to synthesize polysubstituted-1-indanones

An electronic tuning Nazarov-type cyclization protocol was proposed for the synthesis of polysubstituted-1-indanones from the readily available starting materials 1,4-enediones. AlCl₃ was highlighted as the most efficient promoter for this reaction.     

Sc(OTf)3-catalyzed one-pot ene-Prins cyclization: a novel synthesis of octahydro-2H-chromen-4-ols

(R)-Citronellal undergoes initial ene reaction followed by Prins cyclization with aldehydes in the presence of 5 mol % of scandium triflate at ambient temperature to furnish octahydro-2H-chromen-4-ols in good yields and with high cis-selectivity. The use of scandium triflate makes this procedure simple, more convenient, and practical.     

The role of anhydrous zinc nitrate in the thermal decomposition of the zinc hydroxy nitrates Zn5(OH)8(NO3)2·2H2O and ZnOHNO3·H2O

The steps associated with the thermal decomposition of Zn₅(OH)₈(NO₃)₂·2H₂O and ZnOHNO₃·H₂O are re-examined. Previous reports have suggested that Zn₅(OH)₈(NO₃)₂·2H₂O decomposes to ZnO via two intermediates, Zn₅(OH)₈(NO₃)₂ and Zn₃(OH)₄(NO₃)₂ whereas ZnOHNO₃·H₂O has been reported to decompose to ZnO via a Zn₃(OH)₄(NO₃)₂ intermediate. In this study, we demonstrate using TG, mass spectral analysis of evolved gases and in situ variable temperature powder X-ray diffraction analysis that, in fact, in the decomposition of Zn₅(OH)₈(NO₃)₂·2H₂O an anhydrous zinc nitrate intermediate is also involved. We, additionally, show that the decomposition of ZnOHNO₃·H₂O to ZnO also involves the formation of an anhydrous zinc nitrate intermediate. The anhydrous zinc nitrate formed in both cases is poorly crystallised and this observation may explain why this phase could not be observed by PXRD analysis in the previous studies.     

Construction of a pentacyclic ring system of isoryanodane diterpenoids by SmI2-mediated transannular cyclization

Isoryanodane diterpenoids possess a densely oxygenated and intricately fused pentacycle (ABCDE-ring), although its unique ring system has not yet been assembled chemically. The 6/5/7-membered BCD-rings of isoryanodanes differ from the 5/6/6-membered rings of the structurally-related ryanodanes. We previously achieved the total synthesis of ryanodine and five other ryanodane diterpenoids by employing the common ABDE-tetracyclic intermediate 1. Herein, we report a new strategy for constructing isoryanodane ABCDE-ring structure 3 from 1 via a combination of the oxy-Cope rearrangement and SmI₂-mediated transannular cyclization.     

PhI(OAc)2-mediated iminobromination for synthesis of bromomethyl cyclic imines starting from alkenyl carbonitriles and Grignard reagents

PhI(OAc)₂-mediated iminobromination was developed starting from alkenyl carbonitriles and Grignard reagents. The present transformation is carried out by a sequence of nucleophilic addition of Grignard reagents to alkenyl carbonitriles to form N-H imines and their iminohalogenation by subsequent treatment with PhI(OAc)₂.     

Facile synthesis of polysubstituted 2,3-dihydropyrroles and pyrroles from Mn(OAc)3-promoted oxidative cyclization of alkenes with amines/alkyne esters or enaminone esters

A novel oxidative cyclization of alkenes with amines/alkyne esters or enaminone esters can be efficiently promoted by Mn(OAc)₃, furnishing a series of polysubstituted 2,3-dihydropyrroles in moderate to excellent isolated yields (75–91%). Afterward addition of a suitable oxidant such as K₂S₂O₈ can furnish efficient synthesis of the corresponding polysubstituted pyrroles in a one-pot pathway.     

Synthesis and characterization of carborane-containing poly(hydroxy ethers) with excellent thermal stability

o-Carborane-containing poly(hydroxy ethers)(P1, P2 and P3) were synthesized via "advancement reaction" of o-carborane-containing bisphenol(4) and diglycidyl ether of bisphenols(DGEBA and 1). FTIR and ~(1) H-, ~(13)C-, and ~(11) B-NMR were utilized to characterize the obtained polymers. TGA test was conducted under nitrogen and air. It is found that the shielding effect of carborane moiety on its adjacent aromatic structures contributes to high initial decomposition temperatures, while oxygen in air has an adverse effect on the initial decomposition temperature. The oxygen can combine with polymer chain to form peroxide and hydroperoxide groups, which are more reactive during the degradation process. Besides, o-carborane-containing poly(hydroxy ethers) have high char yield at elevated temperatures. The boron atom combines with oxygen from the polymer structure or/and from air, thus to form a three-dimensional network linked with B―O―B and B―C bonds, and retain the polymer weight to a large extent.     

Bi(OTf)3-catalyzed allylation of epoxides: a facile synthesis of homoallylic alcohols

Epoxides react smoothly with tetraallyltin in the presence of 2 mol% of Bi(OTf)₃ under mild reaction conditions to afford the corresponding homoallylic alcohols in excellent yields with high regioselectivity while aryl aziridines produce exclusively allyl amines in good yields under similar conditions.     

以[Eu(PBrBA)3phen]和[Eu(PCBA)3phen]为探针的温敏漆制备及其性能对比

以氧化铕(Eu_2O_3)、对氯苯甲酸(PCBA)、对溴苯甲酸(PBrBA)和菲咯啉(phen)为原料制备了菲咯啉对氯苯甲酸铕[Eu(PCBA)_3phen]、菲咯啉对溴苯甲酸铕[Eu(PBrBA)_3phen]两种探针分子,并将这2种探针分子掺杂在甲基丙烯酸甲酯(MMA)中,以过氧化苯甲酰(BPO)为引发剂,制得Eu(PCBA)_3phen/PMMA和Eu(PBrBA)_3phen/PMMA温敏漆样品。利用红外光谱仪、扫描电子显微镜、紫外-可见分度光度计和荧光光谱仪对探针分子的组成结构、发光性能、形貌和温敏漆的温度敏感性进行了测试分析,研究了不同配体对探针分子发光性能和温敏漆性能的影响。结果表明,Eu~(3+)分别与对氯苯甲酸(PCBA)和对溴苯甲酸(PBrBA) 2种主配体配位,并且第二配体菲咯啉(phen)均参与了配位,成功合成了2种配合物。2种配合物均发出Eu~(3+)的特征荧光,其中以PBrBA为主配体的菲咯啉铕三元配合物具有更好的发光性能。此外,基于这2种探针分子制备的温敏漆在50～90℃范围内均具有温度猝灭性能,以Eu(PCBA)_3phen为探针制成的温敏漆温度敏感性更强。     

Ring opening of epoxides with alcohols using Fe(Cp)2BF4 as catalyst

Fe(Cp)₂BF₄ is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)₂BF₄ as a catalyst (5 mol %) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6 h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol.     

A novel method for correlation of substituent constants in some aromatic esters using the shift reagent Eu(fod)3

The lanthanide induced chemical shifts of the ester methyl group were studied in eighteen m-, and p-substituted aromatic methyl esters with varying amounts of added shift reagent, Eu(fod)₃. Each time the lanthanide induced shift (LIS) was plotted against the molar ratio of shift reagent (SR)/substrate and a straight line was obtained upto one mole ratio of added shift reagent. The slopes of these plots correlated well with the Hammett's σ constants and yield a value of ?4.95 for the reaction constant ?. The method is therefore one of the simplest ways of correlating the substituent constants in aromatic esters.     

[Co(HOC10H6COO)2(H2O)4]配合物的合成、晶体结构和性质研究

Complex [Co(HOC₁₀H₆COO)₂(H₂O)₄] was synthesized by reaction of hydroxy-2-naphthoic acid with CoCl₂·6H₂O. The compound was characterized by elemental analysis, IR and the structure was determined by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P2₁/n with a=0.675 8(2) nm, b=0.518 15(14) nm, c=2.962 9(9) nm, β=94.925(8)°. V=1.033 6(5) nm³, Z=2, D=1.624 Mg·m^-3, F(000)=522. The Co atom has an octahedron coordination geometry and was six-coordinated with two oxygen atoms from two carboxylate ligands and four oxygen atoms from four water molecules. The complex molecules were linked by different hydrogen bonds to form a 2D network. The complex has thermal stability and shows a strong fluorescent emission at 421 nm (λ_ex=342 nm). CCDC: 250903.     

Synthesis of tetrahydroisoquinolines through TiCl4-mediated cyclization and Et3SiH reduction

A versatile and efficient telescoped reaction sequence for the synthesis of tetrahydroisoquinolines(THIQs)is reported that uses TiCl4 to promote cyclization of a benzylaminoacetal derivative and Et3SiH for reduction of the intermediate 4-hydroxy-THIQ.This method is complimentary to the classical Pomeranz-Fritsch and related reactions since it tolerates electron-withdrawing substituents and allows access to 8-substituted THIQs.