675825-21-5Relevant articles and documents
Bidirectional Synthesis, Photophysical and Electrochemical Characterization of Polycyclic Quinones Using Benzocyclobutenes and Benzodicyclobutenes as Precursors
Mohamed Abdelmoniem, Amr,Abdelshafy Abdelhamid, Ismail,Butensch?n, Holger
, p. 6319 - 6333 (2021)
Quinones have widespread applications in view of their interesting chemical and photophysical features. On the other hand, benzocyclobutenes (BCBs) are generally masked reactive dienes suitable for the [4+2] cycloaddition reactions. Here, benzocyclobutenes and benzodicyclobutenes (BDCBs) were prepared and further reacted with benzoquinone and naphthoquinone in order to obtain some new polycyclic quinones with highly extended π systems, namely, 6-bromo-5,8-dimethoxyanthracene-1,4-dione, 2,9-dibromo-1,4,8,11-tetramethoxypentacene-6,13-dione, 9-bromo-7,10-dimethoxytetracene-5,12-dione, 3,10-dimethoxycyclobuta[b]anthracene-1,5,8(2H)-trione, 6,10,17,21-tetramethoxynonacene-1,4,8,12,15,19-hexaone, and 3,12-dimethoxycyclobuta[b]tetracene-1,5,10(2H)-trione. In addition to their spectroscopic characterization the new compounds are investigated by UV and fluorescence spectroscopy, cyclic voltammetry, and DFT calculations.
Arylcalcium iodides in tetrahydropyran: Solution stability in comparison to aryllithium reagents
Langer, Jens,Koehler, Mathias,Fischer, Reinald,Duendar, Feyza,Goerls, Helmar,Westerhausen, Matthias
, p. 6172 - 6182 (2012/10/29)
Reduction of para-substituted iodobenzene in tetrahydropyran (THP) with finely dispersed calcium powder yields arylcalcium iodides of the type [(THP)4Ca(C6H4-4-R)I] with R = CH3 (1), Cl (2), Br (3), I (4), OCH3 (5). A 2-fold insertion of calcium into dihalobenzenes was not observed. The β-naphthylcalcium iodide [(THP)4Ca(β-Naph)I] (6) is also accessible by direct synthesis in THP. The durability of arylcalcium compounds in THP was studied in comparison to that in THF, and a slightly enhanced lifetime in THP at ambient temperature was observed. Furthermore, the relative reactivity and selectivity of 1 and its lithium counterpart [{(THP)2Li}2(μ-Tol)(μ-Br)] (7) in the reaction with THP and THF were studied. α-Metalation and subsequent cycloreversion was the major pathway observed for THF in both cases. In the degradation reaction induced by 7, several byproducts arising from carbolithiation and, surprisingly, from β-metalation reactions were identified, while 1 was found to be more selective. The related [(THP) 2Li(μ-Ph)]2 (9) was prepared and used to unambiguously identify some of the products. In order to verify the formation of benzyllithium as one of the byproducts, an authentic sample of [(dme)Li(μ-CH 2Ph]2 (8) was prepared. In THP, an inversion of the relative reactivity of 1 and 7 was observed and the calcium compound was found to be more reactive than its lithium analogue. The crystal structures of 1-9 were determined by X-ray diffraction studies, and a trans arrangement of the anionic ligands due to electrostatic reasons was observed in case of the hexacoordinated calcium complexes.
Allylic vs. Vinylic Deprotonation Reactions of Cyclic Vinyl Ethers. 7-Lithio-2,3,4,5-tetrahydrooxepin: Synthesis and Carbon-13 Nuclear Magnetic Resonance Spectrum
Oakes, Fred T.,Yang, Fu-An,Sebastian, John F.
, p. 3094 - 3097 (2007/10/02)
2,3,4,5-Tetrahydrooxepin treated with either n-butyllithium or tert-butyllithium affords 7-lithio-2,3,4,5-tetrahydrooxepin.The question of allylic vs. vinylic deprotonation of cyclic vinyl ethers was examined by varying ring size and degree of unsaturation.Carbon-13 spectral data for the anions obtained from 2,5-dihydrofuran, 2,3-dihydrooxepin, and 2,3,4,5-tetrahydrooxepin are reported.In contrast to 2,3,4,5-tetrahydrooxepin, 2,3-dihydrooxepin undergoes allylic deprotonation, possibly as a result of a slightly larger C-C=C bond angle in the dihydrooxepin as compared to that of the tetrahydrooxepin.
