基于2-(3-氧代-2,3-二氢-1 H-环戊[ b ]萘-1-亚烷基)丙二腈的新型推挽染料:一种胺定向合成
摘要:
使用2-(3-氧代-2,3-二氢-1 H-环戊[ b ]萘-1-亚烷基)丙二腈作为电子受体设计了一系列十二种染料。当使用哌啶作为Knoevenagel反应的经典碱时,发生了胺对形成的推挽生色团的亲核攻击,产生了氮杂芴酮衍生物。通过改变胺,可以获得一系列的氮杂芴酮。通过使用扩展共轭的醛,还可以证明环化反应后的自发芳构化。检查了不同染料的光学,电化学性质。还进行了理论计算以支持实验结果。
Carbonyl- and Carboxyl-Substituted Enediynes: Synthesis, Computations, and Thermal Reactivity
摘要:
The influence of electron-withdrawing groups (carbonyl and carboxyl) at the alkyne termini on the reactivity of enediynes was investigated by a combination of experimental and computational techniques. While the general chemical reactivity of such enediynes, especially if non-benzannelated, is increased markedly, the thermal cyclization, giving rise to Bergman cyclization products, is changed little relative to the parent enediyne system. This is evident from kinetic measurements and from density functional theory (DFT, BLYP/6-31G* + thermal corrections) computations of the experimental systems which show that the Bergman cyclization barriers slightly (3-4 kcal/mol) increase, in contrast to earlier theoretical predictions. The effect on the endothermicities is large (Delta DeltaH(r) = 7-12 kcal/mol). Hence, the increased reactivity of the substituted enediynes is entirely due to nucleophiles or radicals present in solution. This was demonstrated by quantitative experiments with diethylamine and tetramethyl piperidyl oxide (TEMPO) which both give fulvenes through 5-exo-dig cyclizations.
Synthesis of phthalic acid derivatives <i>via</i> Pd-catalyzed alkoxycarbonylation of aromatic C–H bonds with alkyl chloroformates
作者:Gang Liao、Hao-Ming Chen、Bing-Feng Shi
DOI:10.1039/c8cc06663a
日期:——
A Pd(II)-catalyzed alkoxycarbonylation of aromatic C–H bonds with alkylchloroformates has been developed. A broad range of benzamides and alkylchloroformates are compatible with this protocol. The reaction is operationally simple and scalable. The direct group could be readily removed to access substituted phthalic acid esters (PAEs), 1,2-dibenzyl alcohols and phthalamides. Besides alkoxycarbonylation
A nondirected dehydrogenative direct alkenylation of simple aromatic compounds with alkenes under rhodium catalysis is described. The site-selectivity is dominantly dictated by the steric bulkiness...
Facile Sc(OTf)<sub>3</sub>-Catalyzed Generation and Successive Aromatization of Isobenzofuran from <i>o</i>-Dicarbonylbenzenes
作者:Yuta Nishina、Tatsuya Kida、Tomonari Ureshino
DOI:10.1021/ol201479p
日期:2011.8.5
Isobenzofuran can be prepared from o-phthalaldehyde using hydrosilane. The formed isobenzofuran is trapped by an alkene via a Diels–Alder reaction. Further dehydration proceeds to furnish the conjugated aromatic compound. This multistep reaction was promoted by catalytic amounts of Sc(OTf)3.
Starting from aromaticortho-dialdehydes, we devised a homo-elongation protocol that combines a Wittig olefination and subsequent intramolecular Knoevenagel condensation to produce acene diesters and dinitriles.
The reaction of silyl-substituted carbanion 1b with arene-1,2-dicarboxylates 6, 15 yields indenone derivatives 11, 16 in a domino process involving silyl C→O migration and elimination. However, in a competing pathway, the initial addition of 1b leads to lactone formation (8, 17). Substrates 26, 38 containing an ester group and a bromine substituent react with 1b under substitution of the halogen not