Microwave-assisted InCl3-catalyzed Meyer-Schuster rearrangement of propargylic aryl carbinols in aqueous media: a green approach to α,β-unsaturated carbonyl compounds

A novel, efficient, simple and environmentally benign protocol for the Meyer-Schuster isomerization of propargylic aryl carbinols into α,β-unsaturated carbonyl compounds has been developed using catalytic amounts of InCl₃, pure water as the solvent, and microwave irradiation as the heating source.     

N-叔丁基苯基呋喃甲酰肼的合成研究

N-叔丁基苯基呋喃甲酰肼是具有良好生物活性的含呋喃环双酰肼类昆虫生长调节剂(IGRs)的重要中间体,可由酰氯与叔丁基肼发生亲核反应制得。通过反应条件探索,获得了同时制备N1-叔丁基苯基呋喃甲酰肼和N2-叔丁基苯基呋喃甲酰肼的合成方法,并用此法制备了10个未见报道的新化合物,其结构通过1HNMR、IR、MS及元素分析确证。本文还通过计算化学方法对其反应机理及在不同条件下所生成异构体的现象进行了初步探讨。     

Scope, mechanism and diene inhibition of isomerization of allylic alcohols to saturated ketones catalyzed by ruthenium(II)-cyclopentadienyl complexes

The isomerization of 3-buten-2-ol to butanone catalyzed by Ru(II)Cp-complexes (Cp = η⁵-cyclopentadienyl) with phosphine and amine ligands is described. The reaction catalyzed by [RuCp(MeCN)₃](PF₆) and two equivalents of triphenylphospine is first order in substrate with a k_ini of 0.43 h⁻¹ and an initial TOF of 13,000 h⁻¹. The catalyst precursor complex [RuClCp(dppb)] (dppb = bis(diphenylphosphino)butane) has been characterized by X-ray diffraction. This compound features a seven-membered ring incorporating the ruthenium centre and the dppb ligand.Combination of two equivalents of primary, secondary or tertiary amines and [RuCp(MeCN)₃](PF₆) results in active catalyst precursors. Within each group, increasing the bulk of the ligand gives lower isomerization rates. The combined effects of optimal pK_a, nucleophilicity and steric bulk make RuCp-complexes with secondary amines the most active precursors. With di-n-butylamine, 745 turnovers can be reached after 1 h. ³¹P NMR spectra indicate that the resting state in the catalytic cycle is a complex in which 3-buten-2-ol is η²-coordinated through the alkene moiety. This implies that coordination of the oxygen moiety and concomitant β-hydrogen abstraction is the rate-limiting step. A counterintuitive result is that allylic alcohols bind stronger to RuCp complexes with phosphine ligands than dienes. Inhibition of the catalyst appears to be a result of interaction of the diene with a ruthenium-allyl alcohol complex, which is sufficiently strong to prevent coordination of the oxygen moiety of the allylic alcohol. This hinders orientation of the allylic alcohol substrate in a suitable way to undergo β-hydrogen abstraction, thereby blocking isomerization catalysis.     

Isomerization Polymerization of Lactams

Isomerization polymerization affords a macromolecule whose repeating unit is derived from an isomer of the original monomer. Thus hexa- and heptacyclic β-carboxymethyllactams yield polymers containing glutarimide units, whereas penta- and hexacyclic β-carboxylactams furnish polymers containing succinimide units. Some dimethyl derivatives of β-carboxylactams isomerize or rearrange, and 5-oxopyrrolidine-3-acetic acid does not react at all. These observations can be explained in terms of a bicyclic intermediate.     

C 78 IPR fullerenes: Computed B3LYP/6-31G*//HF/3-21G temperature-dependent relative concentrations

The five isolated-pentagon-rule (IPR) satisfying isomers of C₇₈, labeled 1-5, or according to symmetry as D₃, C_2v, C' _2v , D_3h, and D' _3h , are computed. The cage geometries are optimized at the ab initio HF level with the standard 3-21G basis set (HF/3-21G). The separation energetics is then computed using the B3LYP density-functional treatment in the standard 6-31G* basis set (B3LYP/6-31G*//HF/3-21G). Harmonic vibrational frequencies are calculated by the SAM1 semiempirical method. The computed energies, structural and vibrational data are employed in the construction of isomeric partition functions and evaluation of the relative Gibbs free energies. The results are converted into relative concentrations for a wide temperature interval. The C' _2v structure is the most populated throughout while the D_3h species is negligible at all temperatures. The agreement between theory and experiment is reasonable, though some aspects are still to be clarified. Received 28 November 2000     

HFSiS构型及其稳定性的理论研究

The structures and stability of triplet HFSiS system were investigated by density functional theory（DFT）in detail. The optimized geometrical parameters and vibrational frequencies of all species were obtained at the level of B3LYP/6-311G** and the assignments of them were performed. At the same theoretical level, IRC calculations were carried. In addition, the singlet-point energies and relative energies were calculated by high level electron-correlation CCSD（T）/6-311G**. The isomerized and dissociated processes were explained by vibrational mode analysis method. The triplet PES is compared to the singlet one. The results are as the following: there are six isomers on the triplet PES. Moreover, 3HFSiS is found to be the most thermodynamically and kinetically stable and is able to be observed in experiments. Structures 2 are the more stable ones between the two group bond cycled isomers and are predicted to be detected. 3SiSHF is the most unstable isomer in thermodynamics and kinetics.     

合成光学活性菊酸酯的方法

Ｌ－孟醇与过量外消旋菊酰氯反应表现出非对映异构体选择性,得到了光学活性菊酸的Ｌ－孟醇酯。由外消旋菊酸的Ｌ－孟醇酯经异构化反应也得到了光学活性菊酸的Ｌ－孟醇酯。     

Integration of nitrogen into coronene bisimides

N-Decorated PBIs and CBIs have been synthesized by the combination of Pictet-Spengler condensation and subsequent oxidative aromatization based on highly electron-deficient amino-PBIs. A detailed analysis of their photophysical properties and molecular crystals has shown that the lateral aryl groups appended on the N-heterocycle have a negligible effect on their optical absorptions and electrochemical potentials, but the subtle modification leads to significant variations on arrangement in the solid state.     

Synthesis of β,γ-unsaturated primary amides from α,β-unsaturated acids and investigation of the mechanism

α,β-Unsaturated acids, through their acid chlorides, react with tritylamine in the presence of triethylamine under mild conditions, to afford in high yield and high regioselectivity the corresponding β,γ-unsaturated tritylamides. Detritylation with TFA generates quantitatively β,γ-unsaturated primary amides. An investigation of this deconjugative isomerization was performed.