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1.
A new methodology for the synthesis of 2,2-disubstituted 2H-chromenes was developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. Phosphazene P2-tBu efficiently catalyzed the addition reaction of 4H-chromen-4-ols containing a diethoxyphosphoryl group with α,β-unsaturated ketones, which involved the catalytic generation of a carbanion through the [1,2]-phospha-Brook rearrangement and subsequent conjugate addition at the 2-position to afford adducts possessing an alkenylphosphate moiety in a highly diastereoselective manner. Further transformation of the adducts based on a nickel-catalyzed cross-coupling reaction with arylzinc reagents provided densely functionalized 2,2-disubstituted 2H-chromenes.  相似文献   
2.
Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional molecules represents an extremely useful process in organic synthesis. Herein, we describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio- and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcohols. Control experiments demonstrated that the key to this high reactivity and selectivity is the addition of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex molecules. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be especially useful in a lead optimization program.  相似文献   
3.
Chemiluminescence (CL) is a luminescence phenomenon originated by a “chemical reaction.” CL provides a basis for real-time imaging technology in materials science. In fact, a CL reaction is easily triggered in general and makes it possible to track its progress in a target material by highly sensitive photon detection. Recently, real-time CL imagings became breakthrough techniques for analyzing the molecular mechanisms of failures of polymeric materials and of reactions and phase transitions in soft crystals. In the CL imaging techniques, adamantylideneadamantane 1,2-dioxetane (Adox) has been adopted as a stable core structure of chemiluminophores. That is, Adox is an essential seed compound to design a chemiluminophore with a desired molecular function. To support developments of real-time CL imaging techniques, we review the chemistry of Adox as a representative stable chemiluminophore including scientific history and utilities of Adox and its derivatives.  相似文献   
4.
The lability of B=B, B?P, and B–halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes undergo cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange.  相似文献   
5.
The imidazo[1,2‐a]pyridines are an important target in organic synthetic chemistry and have attracted critical attention of chemists mainly due to the discovery of the interesting properties exhibited by a great number of imidazo[1,2‐a]pyridine derivatives. Although lots of synthetic methods of imidazo[1,2‐a]pyridines have been developed in the past years, the chemistry community faces continuing challenges to use green reagents, maximize atom economy and enrich the functional group diversity of product. Undoubtedly, with its low cost and lack of environmentally hazardous byproducts, cascade reactions and C?H functionalizations are ideal strategies for this field. In this record we highlight some of our progress toward the goal to synthesis of imidazo[1,2‐a]pyridine derivatives through carbene transformations or C?H functionalizations.  相似文献   
6.
The stereospecific 1,2-migration of boronate complexes is one of the most representative reactions in boron chemistry. This process has been used extensively to develop powerful methods for asymmetric synthesis, with applications spanning from pharmaceuticals to natural products. Typically, 1,2-migration of boronate complexes is driven by displacement of an α-leaving group, oxidation of an α-boryl radical, or electrophilic activation of an alkenyl boronate complex. The aim of this article is to summarize the recent advances in the rapidly expanding field of electrophile-induced stereospecific 1,2-migration of groups from boron to sp2 and sp3 carbon centers. It will be shown that three different conceptual approaches can be utilized to enable the 1,2-migration of boronate complexes: stereospecific Zweifel-type reactions, catalytic conjunctive coupling reactions, and transition metal-free sp2–sp3 couplings. A discussion of the reaction scope, mechanistic insights, and synthetic applications of the work described is also presented.  相似文献   
7.
Abstract

Treatment of the starting complex [Fe2(CO)6{μ-SCH2CH(CH2OH)S}] (1) with 2-(diphenylphosphino)benzoic acid in the presence of N,N’-dicyclohexylcarbodiimide and 4-dimethylaminopyridine gave the corresponding ester derivative [Fe2(CO)6{μ-SCH2CH(CH2O2CC6H4PPh2-2)S}] (2) in 92% yield. Further treatment of complex 2 with one equivalent of Me3NO · 2?H2O as the decarbonylating agent yielded diphenylphosphino-substituted complex [Fe2(CO)5{μ-SCH2CH(CH2O2CC6H4PPh2-2)S}] (3) in 79% yield. Both complexes were characterized by elemental analysis, spectroscopy, as well as by X-ray crystallography. Additionally, the electrochemical properties of these complexes were studied by cyclic voltammetry.  相似文献   
8.
Supported cobalt amorphous catalysts Co-B/γ-Al2O3 were prepared using an impregnation-chemical reduction method for liquid phase hydrogenation of ethyl lactate to 1,2-propanediol (1,2-PDO). The Co-B/γ-Al2O3 catalysts were characterized using inductively coupled plasma (ICP) optical emission spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and X-ray photoelectron spectroscopy (XPS). The effects of the catalyst preparation conditions on the hydrogenation of ethyl lactate were investigated. All the fresh catalysts showed an amorphous structure and Co-B particles were dispersed uniformly on the γ-Al2O3 support. The thermal stability of the amorphous catalyst and the Co/B atomic ratio of surface composition increased with increasing the Co content. The Co-B/γ-Al2O3 amorphous catalyst showed the highest catalytic activity when the theoretical loading of metal Co was 30% (mass fraction, w). The ethyl lactate turnover frequency (TOF), conversion, and selectivity to 1,2-PDO reached 1.41 h-1, 93.63%, and 96.10%, respectively at a reaction temperature of 160 ℃ and hydrogen pressure of 6.0 MPa for 9 h. The higher catalytic performance of the 30%(w) Co-B/γ-Al2O3 supported amorphous catalyst is attributed to its highly dispersing Co-B particles, higher Co/B atomic ratio of surface composition, and electron transfer effect between Co and B.  相似文献   
9.
A novel nanomagnetic basic catalyst of caesium carbonate supported on hydroxyapatite‐coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (Ni0.5Zn0.5Fe2O4@HAP‐Cs2CO3) was prepared. This new catalyst was fully characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X‐ray diffraction and vibrating sample magnetometry techniques, and then the catalytic activity of this catalyst was investigated in the synthesis of 1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione derivatives. Also, Ni0.5Zn0.5Fe2O4@HAP‐Cs2CO3 could be reused at least five times without significant loss of activity and could be recovered easily by applying an external magnet. Thus, the developed nanomagnetic catalyst is potentially useful for the green and economic production of organic compounds. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
10.
α,β‐Unsaturated N‐benzenesulfonyl imine 1 was treated with 1.1 eq methyllithium to afford 1,2‐addition adduct as a sole product. However, when compound 1 was treated with 2 eq MeLi, 1,2‐addition product, benzenesulfonamide derivative 3 and 2H‐1,2‐benzothiazine 1,1‐dioxide derivatives 4 and 5 were isolated.  相似文献   
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