Engineering reactions in crystals: suppression of photodecarbonylation by intramolecular β-phenyl quenching

The photochemical reactivity of cis- and trans-2-(p-carboxybenzyl)-2,6-diphenyl-6-vinylcyclohexanone, cis-1 and trans-1, was investigated in solution and in the crystalline solid state. Photochemical decarbonylation in solution proceeded in excellent yields to give cis- and trans-1-(p-carboxybenzyl)-1,2-diphenyl-2-vinylcyclopentanes cis-2 and trans-2 along with 3-(p-carboxybenzyl)-1,3-diphenylcycloheptene 3. Reactions in crystals were suppressed by a stereospecific quenching interaction between the benzyl substituent and the carbonyl oxygen in the crystalline ketone.     

Spectrophotometric evidence for the existence of rotamers in solutions of some ketocyanine dyes

The existence of rotational conformers in solutions of 1,5-bis[dialkylaminophenyl]-1,4-pentadien-3-one (I) was investigated by infrared, absorption and fluorescence spectroscopy. Comparison was made with 2,5-bis{[4-(dialkylamino)phenyl]-methylene}-cyclopentanone (II) and 2,6-bis{[4-(dialkylamino)phenyl]-methylene}-cyclohexanone (III) which may be considered as rigidified analogues of I. The study in organic solvents revealed that two different conformers coexisted in solutions of I. They differ by rotation about the carbonyl-carbon quasi-single bond and, according to spectroscopic data and AM1 calculations, could be cis, cis and cis, trans isomers, the latter being found in much larger proportions.     

A novel, versatile synthetic approach to linearly fused tricyclopentanoids via photo-thermal olefin metathesis

Fifteen examples of a new, speedy and general approach to linearly fused tricyclopentanoids bearing the tricyclo[6.3.0.0^2,6]undecane (triquinane) frame of high contemporary interest is delineated. The key concept in our synthetic sequence to triquinanes is the novel photo-thermal olefin metathesis of cheap, abundantly available Diels-Alder adducts of 1,3 cyclopentadienes and p-benzoquinones. Thus photolysis of endo-tricyclo[6.2.1.0^2,7] undeca-4,9-dien-3,6-diones (9a–9j, 13a,b) furnished pentacyclo [5.4.0.0^2,6.0^3,10.0^5,9]undecan-8,11-diones (10a–10j, 14a,b), which on thermal fragmentation of the cyclobutane ring gave cis, syn, cis-tricyclo [6.3.0.0^2,6]undeca-4,9-dien-3,11-diones (11a–11j, 15a,b in just three steps and in exceptionally good yields. A few interesting transformations of the readily available parent bis-enone 11a which indicates its wider uses in syntheses, are described. Finally, a smooth thermal isomerisation of cis, syn, cis-bis-enones to cis, anti, cis-bis-enones is reported, which further enhances the scope and versatility of our synthetic theme.     

吡啶双亚胺酰氯Ni(Ⅱ)配合物的合成、 表征及催化合成液体聚丁二烯

合成了一系列吡啶双亚胺酰氯三齿Ni(Ⅱ) 配合物(1a~1c, 2a~2c), 通过傅里叶变换红外光谱和元素分析对配合物进行表征, 测定了配合物1a~1c的晶体结构. 3个化合物同属于单斜晶系, 且都具有以Ni原子为中心的近似于C_s对称的扭曲三角双锥构型. 该系列配合物通过倍半乙基氯化铝(EASC)活化, 在20 ℃下对丁二烯聚合表现出良好的催化活性, 得到分子量为4700~5200、 cis-1,4含量为74.8%~77.2%(摩尔分数)的液体聚丁二烯. 通过改变配体的结构和聚合条件, 可在一定范围内调控聚丁二烯的结构和分子量.     

Studies on the reactivity of methyl γ-tosylcrotonoate as ambident reagent in organic synthesis

The treatment of methyl(E)-4-tosyl-2-butenoate (4) with two equiv. of sodium hydride and different mono and dihalides gives mainly γ,γ- and ,- or ,γ- and ,-dialkylated products (5–7) depending on the electrophile. The corresponding monoanion dimerizes with iodine to afford stereoselectively dimethyl cis-4,5-ditosyl-2,6-cyclohexadiene-1,2-dicarboxylate (11). The tosyl group in compounds 6 and 7 is reduced and in the case of γ,γ-dimethylated 5a substituted by sodium dimethyl malonate under Pd(PPh₃)₄ catalysis. Michael addition of different nucleophiles provides the corresponding β-substituted methyl γ-tosylbutanoates 16.     

Platinum(II) substituted pyrrolidine complexes. Crystal structure of dichloride 1,2 diethyl 3 aminopyrrolidine Pt. Reactions with DNA and dinucleotides

The effect of five derivatives of Pt^II, cis dichloro-(1,2-dimethyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1-methyl, 2-ethyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1-ethyl, 2-methyl-3-aminopyrrolidine)platinum(II), cis dichloro-(1,2-diethyl-3-aminopyrrolidine)platinum(II), and cis dichloro-(1-propyl, 2 methyl-3 aminopyrrolidine)platinum(II) on platination of DNA was studied by CD and melting temperature determination. Reactions with the nucleotides d(ApG) and d(ApA) were also followed by ¹H NMR and CD, indicating binding via N(7) and formation mainly of bifunctional, in the case of d(ApG), or monofunctional adducts, in the case of d(ApA). The crystal structure of cis dichloro-(1 ethyl, 2 methyl-3 aminopyrrolidine)platinum(II) shows the analogues cisplatin structure of these active antitumour complexes. This compound is racemic.     

Stereochemical studies of optically active 2-hydroxy-5-alkyl-δ-valerolactone derivatives as chiral dopant for ferroelectric liquid crystals

Both (2S, 5R)- and (2R, 5R)-2-hydroxy-5-alkyl-δ-valerolactone derivatives, cis and trans, respectively, show almost the same magnitude of spontaneous polarization (P_s) when added to a non-chiral smectic C mixture. The stereochemistry of these chiral dopants was studied using ¹H NMR. Trans derivatives seem to have a half-chair conformation with the 2, 5-diequatorial substituents and the cis derivatives have rather a flat conformation in solution. However in the liquid-crystalline phase, the cis and trans derivatives appear to change their conformation or the distribution of their conformations as the alkyl chain length is varied. The difference in the effect as a chiral dopant depends upon lateral interactions between chiral molecules through the solvent liquid crystal phase.     

Synthesis and characterisation of a novel surfactant, sodium geranyl sulphate

An anionic surfactant, sodium geranyl sulphate (sodium 3,7-dimethyl-2,6-octadienyl sulphate), was synthesised from the natural extracted monoterpenol, geraniol. The final product yield is 51.5% after recrystallisation. The cis/trans isomer reduced the surface tension of water to 33 ± 0 mN m⁻¹ and yielded a critical micelle concentration of 89 ± 7 mM.     

Proton magnetic resonance studies of cyclic compounds—III cis- and trans-2,6-dimethylmorpholines

Commercial 2,6-dimethylmorpholine has been separated into cis- and trans-isomers by vapour phase chromatography. The PMR spectra of the bases, analysed as ABXK₃ systems (J_AK = J_BK = 0), show that the most abundant isomer has the cis-configuration, consisting probably of a single conformation in which both methyl groups are equatorial. The trans-isomer is probably a mixture of rapidly inverting and energetically equivalent conformations, since the vicinal coupling constants deduced from the PMR spectrum are averages of those expected for the two conformations.     

Variation of activation volumes for aquation of chloroaminecobalt(III) complexes

Activation volumes for aquation of cis-[Co(en)₂(NO₂)Cl]⁺, trans-[Co(en)₂ (CN)Cl]⁺, cis-- and cis-β-[Co(trien)Cl₂]⁺ have been determined, and are compared with values reported for a range of chloroaminecobalt(III) complexes. Variation of reported ΔV^≠ in terms of, particularly, solvation effects is discussed.     

Stereocontrolled synthesis of (RR)- and (RS)-5-hydroxy-2-methylhexanoic acid lactones : Pheromone of the carpenter bee via palladium-catalyzed reactions

(E,Z)-2,4-Hexadiene was transformed to the lactone cis-1 ( 93% cis)(pheromone of the carpenter bee) in a stereospedfic reaction sequence via a Pd-calalyzed 1,4-acetoxychlorination. The same reaction sequence applied to (E,E)-2,4-hexadiene afforded the isomeric lactone trans-1 (91% trans).     

Enantioselective hydrogen transfer reactions from propan-2-ol to ketones catalyzed by pentacoordinate iridium(I) complexes with chiral Schiff bases

Some diastereoisomeric pentacoordinate complexes of the type [Ir(COD)-(NNR)I] (COD = cis,cis-1,5-cyclooctadiene; NNR = 2-pyridinal-1-phenylethylimine (PPEI) (I), 2-acetylpyridine-1-phenylethylimine (APPEI) (II)) have been synthesized. The complexes are active and selective catalysts for asymmetric hydrogen transfer from propan-2-ol to prochiral ketones. Optical yields of up to 84% have been obtained in the reduction of t-butyl phenyl ketone. The structure and absolute configuration of complexes I and II were determined by X-ray diffraction.     

空间因素对敏化剂性质的影响

本文介绍了一种新的敏化剂cis-(NCS)₂-bis(2,2′-bipyridyl-3,3′-dicar-boxylate)ruthenium(Ⅱ)的合成,测定了它的吸收光谱及氧化还原电位,并将这种染料吸附到具有大比表面的TiO₂纳晶电极上测量它的光电转换效率。另外,参照文献分别合成出cis-(NCS)₂-bis(2,2′-bipyrdyl-4,4′-or 5,5′-dicarboxylate)Ru(Ⅱ)染料,测定它们的光电及光物理性质并以此为依据讨论了空间因素对敏化剂性质的影响。     

Ideal gas state thermodynamic functions for a series of halogenated propenes

The thermodynamic functions, C√_p, S√,—F√_o—H√)/T and (H√—H√_o)/T have been calculated in the ideal gas state at one atmosphere for the following halogenated propenes: cis-1-chloropropene; trans-1-chloropropene; cis-1-bromopropene; trans-1-bromopropene; 2-fluoropropene; 2-chloropropene; 2-bromopropene; 2-iodopropene; cis-3-fluoropropene; gauche-3-fluoropropene; isomeric-3-fluoropropene; mixture; cis-3-chloropropene; gauche-3-chloropropene; isomeric-2-chloropropene mixture; cis-3-bromopropene; gauche-3-bromopropene; isomeric-3-bromopropene; mixture; cis-3-iodopropene; gauche-3-iodopropene and isomeric-3-iodopropene mixture. The agreement with other results, whenever available, is very good.     

Conformational and NBO analysis on cis and trans isomers of methyl-1-(4-hydroxy-3-methoxyphenyl)-1,2,3,4-tetrahydro-9H-β-carboline-3-carboxylate

The cis and trans-methyl-1-(4-hydroxy-3-methoxyphenyl)-1,2,3,4-tetrahydro-9H-β-carboline-3-carboxylates were prepared and ¹H and ¹³C NMR spectra were recorded for both isomers. Conformational and NBO analysis were carried out for the cis and trans isomers. Conformer structures were pre-optimized using the hybrid method B3LYP along with the 6-311+G(d) basis set. Frequency calculations were employed to confirm the structures as minimum points. Potential energy surfaces (PES) were built at the same level of theory. Geometries obtained from DFT calculations were used to perform NBO analysis by the NBO 3.1 module in GAUSSIAN 03. The results obtained through theoretical calculations revealed that the shielding observed at C1 for the trans isomer can be attributed to carbomethoxy γ-effect, together with the hyperconjugative effect, while only hyperconjugative effects were found to explain the shielding of C3. The higher chemical shift value of C3 of the cis isomer was attributed to the carbonyl substituent, which plays an important role by capturing part of the electronic density in C3.     

Synthesis and hydride reductions of chiral cyclic β-iminosulfoxides

The hydride reductions of chiral N-(2-p-tolylsulfinyl)cyclohexylidene phenyl amines 3A and 3B (epimers at C-2), and of N-1-(2-p-tolylsulfinyl)cyclohexenyl benzyl amine, 4, are highly stereoselective, yielding only the corresponding cis-aminosulfoxides.     

Steric effects of the 2-(diphenylphosphino)pyridine bridging ligand in the synthesis of binuclear palladium(II) complexes

Treatment of [Pd{CH₂C(CH₃)CH₂}(Ph₂PPy)Cl] (Ph₂PPy = 2-(diphenylphosphino)pyridine) with cis-[Pd(^tBuNC)₂Cl₂] in dichloromethane affords the mixed isocyanide-tertiary phosphine complex cis-[Pd(^tBuNC)Ph₂PPy)Cl₂], in which the Ph₂PPy is a monodentate P-donor, and [{Pd[CH₂C(CH₃)CH₂]Cl}₂]. The steric effects of the Ph₂PPy bridging ligand in determining the reaction course is discussed. The complex cis-[Pd(^tBuNC)(Ph₂PPy)Cl₂] was crystallographically characterized: P2₁/n, a = 15.143(2), b = 9.527(1), c = 17.517(4) Å, β = 113.96(1)°, V= 2309.4(7) ų, Z = 4. The final R value was 0.044, R^w= 0.046 for the 3078 reflections with I > 3σ(I).     

Convenient diastereospecific synthesis of a rociverine precursor and its resolution by lipase-catalyzed transesterification

(±)-1-Cyclohexyl-c-2-hydroxymethyl-r-1-cyclohexanol 3, a precursor of the antimuscarinic drug Rociverine 1, was obtained diastereospecifically in very high yield, from the Grignard reaction between C₆H₁₁MgCl and an appropriately protected 2-(hydroxymethyl)cyclohexanone. The preparation of enantiomerically enriched cis diol (+)-(1R,2S)-3 and the corresponding 2-acetoxymethyl derivative (+)-(1S,2R)-12 was achieved by lipase PPL-catalyzed transesterification of racemic diol (±)-3.     

Metathesis polymerization of norbornene and terminal acetylenes catalyzed by bis(acetonitrile) complexes of molybdenum and tungsten

The ring-opening metathesis polymerization (ROMP) of norbornene catalyzed by bis(acetonitrile) molybdenum and tungsten complexes, [M(η³-C₃H₅)Cl(CO)₂(NCMe)₂] (1-Mo: M = Mo, 1-W: M = W), which have two labile acetonitrile ligands, has been investigated. These complexes catalyzed the ROMP of norbornene as a single-component initiator. The highly cis-selective polymerization proceeded in a THF solution (95% for 1-Mo and 96% for 1-W), whereas polymerization in CH₂Cl₂ or toluene resulted in lower cis selectivity. The polymerization of terminal acetylenes using these complexes was also examined. The tungsten complex 1-W showed a high catalytic activity for the polymerization of terminal acetylenes, such as phenyl- and tert-butylacetylene. A highly active catalytic system for the ROMP of norbornene was achieved by the activation of the tungsten complex, 1-W, with one equivalent of phenylacetylene, giving poly(norbornene) with a high molecular weight (M_n = 391 × 10⁴) and a high cis selectivity (cis  89%).     

A short, practical synthesis of the ant venom alkaloid, three (3R,5S,8aS)-3-alkyl-5-methylindolizidines

A short, practical and diastereoselective method for preparing the ant venom alkaloid, three (3R,5S,8aS)-3-alkyl-5-methylindolizidines (1–3), has been developed. The stereoselective intramolecular amidomercuration of the N-alkenylurethane 4 followed by oxidative demercuration provides the piperidine alcohol cis-6 as a major product. Thereafter, oxidation of cis-6 followed by the Horner-Emmons elongation of the ring appendages affords the enones 8, 10, and 11, which are stereoselectively converted into 1, 2, and 3, respectively, by catalytic hydrogenation.