A Curtin–Hammett pentamethylene chain symmetrization process in the Bergman cyclization of an 11‐membered ring enediyne

Pentamethylene chain conformational effects for the Bergman cyclization of the 11‐membered ring enediyne, (3Z)‐3‐cycloundecene‐1,5‐diyne, 2, are examined theoretically with unrestricted Becke, three‐parameter, Lee–Yang–Parr/6‐31 G(d,p) calculations. A C₁ symmetric enediyne conformation was found to be the global minimum, where its nonsymmetric pentamethylene chain prevented π‐orbital alignment of the acetylene groups for C–C σ bond product formation. The Bergman cyclization of 2 was found to be conformationally dependent. In a Curtin–Hammett type process, the C₁ symmetric 2 inverts to one of the C_S or C₂ symmetric conformers required for the Bergman cyclization, which produced a C_S or C₂ symmetric 1,4‐diradical intermediate. The activation energy for the cyclization is slightly higher to reach the C₂ symmetry diradical compared with the C_S symmetry diradical. Copyright © 2012 John Wiley & Sons, Ltd.     

Polytriacetylenes bearing directly attached functional groups with tunable physical and electronic properties

We report the synthesis and characterization of a unique class of conjugated polymers, polytriacetyelenes (PTAs), from a set of trans‐enediyne (EDY) monomers bearing alkyl and aromatic substituents. Two different methods, i.e., Glaser‐Hay coupling and Pd‐catalyzed oxidative coupling, were employed depending on the nature of the side‐chains. Our methodology is highly versatile in that it allows direct attachment of aromatic substituents to the PTA main‐chains, allowing enhanced tunability in polymer electronic properties, which has not been achievable through previously reported methods. The newly synthesized PTAs displayed strong ability of quenching the fluorescence of poly(3‐hexylthiophene) (P3HT), a prototypical conjugated polymer in organic solar cells, indicating possible applications of these PTAs in optoelectronic devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1391‐1395     

钯催化下共轭二烯二炔官能团的构成

制备了一系列共轭烯炔化合物以及卤代烯炔化合物,并利用它们在钯催化下交叉偶联构成了与环戊烯共轭骈连的烯二炔即共轭的二烯二炔结构。此结构为抗肿瘤抗生素C-1027发色团和kedarcidin发色团所共有;同时探讨了它们在钯催化下交叉偶连的性质,发现共轭的卤代烯炔与共轭的端炔交叉偶连的趋势为:碘代烯>溴代烯>氯代烯。     

含三唑结构的新型稠合三环2(5H)-呋喃酮衍生物的合成

利用系列含烯二炔结构的2(5H)-呋喃酮衍生物与叠氮化钠发生串联的成环反应, 在优化的反应条件下, 即反应溶剂为DMF、反应时间48 h、反应温度30 ℃时、NaN₃为1.5 equiv., 以中等产率(42%～62%)合成了系列新型的稠合三环2(5H)-呋喃酮衍生物, 其可以进一步高产率地(94%～96%)衍生为吡啶稠合的2(5H)-呋喃酮化合物. 所有新化合物的结构用IR, ¹H NMR, ¹³C NMR, MS, 元素分析等方法进行了表征. 该串联反应合成途径简捷、反应条件温和, 无需添加催化剂, 可为具有含三唑结构的稠杂环化合物合成提供简便的途径.     

(E)-烯二炔化合物的高选择性合成

3-烯-1,5-二炔是许多烯二炔类抗癌抗生素和发光材料的重要片断. 发展了一种高选择性合成E-烯二炔化合物的两步法: (1) CuBr₂为卤化剂, 温和高效合成双卤代烯烃; (2)通过双卤代烯烃和末端炔烃的Sonogashira偶联反应构建烯二炔化合物.     

Transition Metal-Free Regio- and Stereo-Selective trans Hydroboration of 1,3-Diynes: A Phosphine-Catalyzed Access to (E)-1-Boryl-1,3-Enynes

We report a transition metal-free, regio- and stereo-selective, phosphine-catalyzed method for the trans hydroboration of 1,3-diynes with pinacolborane that affords (E)-1-boryl-1,3-enynes. The reaction proceeds with excellent selectivity for boron addition to the external carbon of the 1,3-diyne framework as unambiguously established by NMR and X-ray crystallographic studies. The reaction displays a broad substrate scope including unsymmetrical diynes to generate products in high yield (up to 95 %). Experimental and theoretical studies suggest that phosphine attack on the alkyne is a key process in the catalytic cycle.     

Synthesis of dendronized polymers through bergman cyclization of enediyne‐containing Frechet‐type dendrimers

In this article, dendronized polymers with rigid backbones were synthesized from enediyne‐containing Frechet‐type dendrimers. Two generations of dendrimers were conically incorporated with 3‐(2‐(2‐(trimethylsilyl)ethynyl)phenyl)prop‐2‐yn‐1‐ol. The trimethylsilyl protection groups of enediyne units were subsequently removed, and two types of brush polymers with rigid conjugated backbone were prepared through Bergman cyclization polymerization at elevated temperature under vacuum. The dendronized polymers were characterized with GPC, IR, UV–vis, and NMR spectroscopy. Furthermore, the morphology of the dendronized polymer was revealed by atomic force microscopy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of angularly fused aromatic compounds from alkenyl enediynes by a tandem radical cyclization process

Let's get radical: A general synthetic route toward angularly ortho-fused polyaromatic [4]helicenes starting from aryl alkenyl N-substituted cyclic enediynes is described (see scheme; DMSO=dimethyl sulfoxide, Ns=4-nitrobenzenesulfonyl). The process involved a Bergman cyclization (BC) as the key step of an unprecedented tandem radical reaction.     

Synthesis, reactions and DNA damaging abilities of 10-membered enediyne-sulfone and related compounds

The synthesis and Myers-Saito type cycloaromatization reactions of 10-membered enediynes containing a sulfone or a sulfoxide moiety are described. These enediynes cycloaromatized smoothly under physiological conditions to generate bioactive α,3-didehydrotoluene biradicals, that showed potent DNA damaging abilities. Further, in the presence of a nucleophile such as amine or sulfide, cycloaromatization did not occur following the radical reaction pathway but ionically induced cycloaromatization took place.     

Simultaneous determination of lidamycin enediyne chromophore (LDC) and its aromatized derivative (LDCA) using puerarin as internal standard in rat plasma by LC-MS/MS

Lidamycin (LDM), a promising enediyne antitumor antibiotic, was quantified by detecting lidamycin enediyne chromophore (LDC) using liquid chromatography–tandem mass spectrometry (LC‐MS/MS) for the first time. A simple, rapid and reliable method was developed and validated to determine LDC and its aromatized derivative (LDCA) simultaneously in plasma. Puerarin was used as an internal standard (IS), and plasma samples were pretreated with one‐step precipitation by acetonitrile. Separation was achieved on a reverse‐phase C₁₈ column with a mobile phase composed of methanol and water containing 5 mm ammonium acetate at pH 3.5 in gradient elution mode. Detection was performed on a triple quadrupole tandem mass spectrometer using electrospray ionization (ESI) by multiple reaction monitoring (MRM) in the negative ion mode. Good linearity was obtained over the concentration range of 0.2–100 µg/mL for LDM. Precision and accuracy were validated by RSD% values in the range of 2.6–13.0% and RE% values between ?4.6 and 3.8%, respectively. In addition, no specificity and matrix effects were observed. The recovery was found to be 99.2–111.0% and stability in various conditions was found to be acceptable. This method was applied in preclinical pharmacokinetic studies for routine monitoring of LDM in rat plasma. Copyright © 2011 John Wiley & Sons, Ltd.