环己酮肟在B2O3/Al2O3-TiO2催化剂上的气相Beckmann重排反应

制备了B2O3/Al2O3-TiO2复合载体催化剂,并考察了其对环己酮肟气相Beckmann重排制己内酰胺反应的催化性能. 结果表明,载体中TiO2的含量、B2O3的负载量、载体的预处理温度及催化剂的焙烧温度等均对催化剂的性能产生明显的影响. 当载体中TiO2含量为60%,B2O3负载量为20%,催化剂经350 ℃焙烧时,环己酮肟的气相Beckmann重排反应的转化率和选择性很高. 用BET,NH3-TPD,XRD和IR等方法对催化剂的织构、表面酸性和晶相等进行了表征,并与催化剂的活性进行了关联,表明催化剂表面中等强度的酸中心浓度与催化剂的选择性具有对应关系.     

Stable meso‐Aryl β‐Alkyl Hybrid Sapphyrin with a Warped π‐Conjugation Circuit and Neo‐Confused Sapphyrin–Silver(I) Complex

A meso‐aryl and β‐alkyl substituted sapphyrin and its rhodium(I) and silver complexes were synthesized. This sapphyrin was so stable that the non‐inverted and warped structure could be analyzed by X‐ray crystallography even in its neutral state. Its bis‐rhodium(I) complex has a more planar structure than the sapphyrin with enhanced aromaticity over the conjugation circuit. On the other hand, silver metalation of the sapphyrin caused a marked core rearrangement into a neo‐confused sapphyrin derivative with a C(α)?N bond and a twisted macrocycle.     

Synthesis of Phaitanthrin E and Tryptanthrin through Amination/Cyclization Cascade

Phaitanthrin E was biomimetically synthesized from methyl indole‐3‐carboxylate and methyl anthranilate or anthranilic acid using the ester group as an activating group. The reaction proceeds through NCS‐mediated dearomatization/TFA‐catalyzed protonation of indolenine/C(2) amination/Et₃N‐promoted aromatization and cyclization in one‐pot procedure. This method is capable of converting simple biomass materials to phaitanthrin E. The synthesis not only allows assessment of antiproliferative activity, but also affords experimental support for the hypothetical biosynthetic pathway of phaitanthrin E. The resulting phaitanthrin E derivatives were evaluated for in vitro antiproliferative activity against human colorectal cancer cells (DLD‐1). The biogenetic intermediate of phaitanthrin E showed higher antiproliferative activity than the natural product, phaitanthrin E. Furthermore, a concise synthesis of tryptanthrin is also accomplished from indole‐3‐carbaldehyde and methyl anthranilate using the aldehyde group as an activating group.     

钴催化的高效贝克曼重排反应

利用廉价易得的氟硼酸钴水合物, 在温和、 无添加剂的空气条件下, 高效催化酮肟衍生物的贝克曼重排反应, 底物的普适性和官能团的兼容性均较理想, 产物收率最高达97%. 基于该高活性的氟硼酸钴水合物, 实现了10 g级二苯甲酮肟的贝克曼重排反应, 收率为71%. 同时, 也实现了钴催化酮类衍生物和盐酸羟胺的一步法贝克曼重排反应, 产物最高收率为94%, 反应体系中无溶剂及添加剂, 反应体系的原子经济性和底物普适性较好.     

A Diels-Alder reaction / oxa-Michael addition / acyloin rearrangement cascade on tropolonic substrates

We describe a novel pericyclic/anionic cascade reaction on tropolonic substrates that combines a Diels-Alder reaction, an oxa-Michael addition, and an acyloin rearrangement to afford tricyclic α-hydroxy-β-methoxyketones. Spectroscopic, crystallographic, and mechanistic studies indicate that the process requires stabilization of reaction intermediates through intramolecular H-bonding to take place, and suggest that the conjugate addition step involves a catalytic cycle with initial formation of an ammonium enolate and sustained by an alkoxide ion pair. Given the rich functionality and structural complexity generated in a single step, the process could be exploited in the preparation of natural product-like compound libraries.     

Ruthenium‐Catalyzed Cascade Annulation of Indole with Propargyl Alcohols

Cascade transformations forming multiple bonds and one‐pot procedures provide rapid access to natural‐product‐like scaffolds from simple precursors. These atom‐economic processes are valuable tools in organic synthesis and drug discovery. Herein, we report on ruthenium‐catalyzed cascade annulations of indole with readily available propargyl alcohols. These provide rapid access to diverse carbazoles, cyclohepta[b]indoles, and further fused polycycles with high selectivity. A bifunctional ruthenium complex featuring a redox‐coupled cyclopentadienone ligand acts as a common catalyst for the different cascade processes.     

Rearrangement ofO-perfluoroisobutenylacetone oxime. The structure of 2,2-bis(trifluoromethyl)-5-methyl-gD4-pyrrolin-3-one

Dehydrofluorination ofO-(-hydroperfluoroisobutyl)acetone oxime affords 2,2-bis(tri-fluoromethyl)-5-methyl-⁴-pyrrolin-3-one; the molecular structure of the latter was unambiguously established by X-ray diffraction method.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 951–953, May, 1994.     

Synthesis of chiral alkenyl epoxides: the sex pheromone of the elm spanworm Ennomus subsignaria (Hübner) (Lepidoptera: Geometridae)

The identification of the sex pheromone of the elm spanworm Ennomos subsignaria (Hübner), as the chiral alkenyl epoxide (6Z)-cis-9,10-epoxy-nonadecene has been accomplished. Both enantiomers of (6Z)-cis-9,10-epoxy-nonadecene have been synthesized via two routes. The key steps in the first route were to prepare both threo-epoxy tosylates and then to perform an alkylative rearrangement of these intermediates to obtain the target molecules. An alternative enantioenriched synthesis that took advantage of the Sharpless dihydroxylation reaction was developed so that a common starting material could be used to access both enantiomers. A field study and GC/EAD testing indicated that Z6-cis-9S,10R-epoxy-nonadecene was the sex pheromone of the elm spanworm E. subsignaria (Hübner).     

A novel Barton decarboxylation produces a 1,4-phenyl radical rearrangement domino reaction

A novel 1,4-Phenyl radical rearrangement (1,4-PhRR) is described in a typical Barton decarboxylation procedure. While carrying out this reaction in presence of a N,N-disubstituted β-amino acid derivative, the decarboxyphenyl rearranged derivative is obtained, as well as in presence of β-N,N-acylamide. On the other hand, secondary amines give the β-lactam derivative without rearrangement, as well as N-Fmoc derivatives give the normal decarboxylation reaction. In regards of amines which are far away from the carboxylic group, such as δ-amino acid derivatives, the reaction occur through a typical Barton decarboxylation without rearrangement. The diversity of the reaction proves synthetic usefulness paving the way to interesting biologically active compounds.