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51.
Rolf Huisgen 《Angewandte Chemie (International ed. in English)》1980,19(12):947-973
The principle of orbital control of pericyclic reactions has deepened our understanding of reaction phenomena and provided an excellent classification of these one-step processes. The electrocyclic reaction of the pentadienyl anion ? cyclopentenyl anion type is relatively unimportant in all-carbon systems and has not even been verified in the case of the parent compound. In the heterocyclic series, however, where up to five C-atoms of the pentadienyl anion are replaced by heteroatoms, a multitude of ring closures and ring openings find their ordering principle in the mentioned electrocyclic reaction. The replacement of the carbon atoms by heteroatoms can take place isoinically, i. e., with retention of the anionic character, or isoelectronically. An isoelectronic replacement of CR2 in position 1 by NR2 OR, and or CR in position 3 by NR or O leads to a charge-free resonance structure for the open-chain species; the migration of the charge during the electrocyclization results in a correlation with a cyclic zwitterion. Conversely, isoelectronic exchange of CR in position 2 by NR or O produces a conjugated 1,3-dipole, which cyclizes to a charge-free unsaturated five-membered ring. Twofold isoelectronic exchange allows the whole process to take place in a cation. Selected examples are to shed light on the classification and the thermodynamics of this electrocyclic reaction. 相似文献
52.
An electrochemical synthesis of oxazol‐2‐ones and imidazol‐2‐ones has been developed via 5‐exo‐dig cyclization of propargylic carbamates‐ and ureas‐derived amidyl radicals. The electrosynthesis relies on the dual function of 2,2,6,6‐tetramethylpiperidin‐ 1‐yl)oxyl (TEMPO) as a redox mediator for amidyl radical formation and an oxygen atom donor. The reactions are conducted under mild conditions using a simple setup and provide convenient access to functionalized oxazol‐2‐ones and imidazol‐2‐ones from readily available materials. 相似文献
53.
Alexander V. Butin Vladimir V. Mel'chin Wolfgang Bender Gennady D. Krapivin 《Tetrahedron》2006,62(34):8045-8053
The synthesis of a number of naphtho[2,3-b]furan derivatives, containing a furyl substituent in position 9 by intramolecular cyclization of 2-carboxy and 2-formylbis(5-alkylfur-2-yl)methanes is described. The reactivity of the title compounds in formylation, acetylation, nitration, and oxidation reactions has been investigated. It was shown that nitration of 2-methyl-9-(5-methyl-2-furyl)naphtho[2,3-b]furan-4-yl acetate leads to oxidative furan ring opening rather than to electrophilic substitution. 相似文献
54.
Cathodic reduction of phenacyl bromides N-acyl hydrazones lead to dimeric 1,4-diaryl-1,4-butanedione di-N-acylhydrazones, which give the corresponding 1-N-acylamino-2,5-diarylpyrroles in good yields. 相似文献
55.
We report here the first example of a one-pot synthesis of 2-(alkyl)arylbenzoselenazoles from N-(acetyl)benzoyl-2-iodoanilines. The reaction was carried out in the presence of Woollins’ reagent under microwave irradiation and resulted in moderate to good yields. 相似文献
56.
Majid M. Heravi Mohammad Rahimizadeh Effat Iravani Mitra Ghassemzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):797-802
The synthesis of bicyclic compounds derived from benzo[1,2,4]triazines is described. 相似文献
57.
58.
Pd(0)-catalyzed carboiodonation of but-3-enylcarbamic chloride has been developed with NaI as additive, which provides a ready access to substituted γ-lactam bearing an alkyl iodide group. This reaction features alkyl iodide reductive elimination as a key step in catalytic cycle, indicating the crucial role of additive NaI. 相似文献
59.
G. V. P. Chandramouli B. Prasanna P. Naveen Kumar P. Vijayakumar Reddy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):511-522
The key step for the synthesis of 7-hydroxy 2,3-diarylsubstituted benzothiophenes 5a-f , by starting from substituted 2-aryl-2-((2-methoxy phenyl)thio)acetophenones 3a-f as an intermediate, consists of a Friedel-Crafts cyclization followed by demethylation by Lewis acids like BF 3 OEt 2 and AlCl 3 in DCM. 相似文献
60.
M. Hannoun N. Blažević D. Kolbah F. Kajfež 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):125-126
Abstract Bis(trimethylsilyl)peroxide (BSPO) can be used for chemo- and stereoselective generation of P=O group by oxygenation of P(III) centre and transformation of P=S and P=Se groups. 相似文献