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1.
Jinxiong Lin Dr. Nathan T. Coles Lea Dettling Luca Steiner Dr. J. Felix Witte Prof. Dr. Beate Paulus Prof. Dr. Christian Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(72):e202203406
A 3-amino-functionalized phosphabenzene (phosphinine) has been synthesized and structurally characterized. The pyramidalized nitrogen atom of the dimethylamino substituent indicates only a weak interaction between the lone pair of the nitrogen atom and the aromatic phosphorus heterocycle, resulting in somewhat basic character. It turned out that the amino group can indeed be protonated by HCl. In contrast to pyridines, however, the phosphabenzene-ammonium salt undergoes a selective ring contraction to form a hydroxylphospholene oxide in the presence of additional water. Based on deuterium labeling experiments and quantum chemical calculations, a rational mechanism for this hitherto unknown conversion is proposed. 相似文献
2.
《中国化学快报》1999,(8)
Previouspublications'fromourlaboratoryhadreportedtheringenlargementreactionofquatemaryarnrnoniumsaltSofN-methyl-tetTahydroisoquinolinefollowedbyreductivedecyanationwiththenetresuItoftheinserti0nofanextraCH2group,assh0wninSckemeI.ThemethodologyfailedwithsomenatUrallyoccurringalkaloidssuchascephalotaxineandatropine'.Onereasonisthatsomeofthequaternaryammoniumsaltsaredifficulttoprepare,theotheroneisthatsome0fthequaternaryafnmoniumsaItsunderwentHofinarineliminationorSofnmeletrearrangement'.But… 相似文献
3.
Xiao-Tian Liang 《中国化学会会志》1995,42(4):601-605
This review describes our preliminary results of ring enlargement of N-heterocycles by N-ylide formation at a targeted site, exemplified by 55→56→58. Before development of this method, the strategy can be traced to our modified Hofmann degradation led at first to several miscarried probings on the reaction between N-halomethyl ammonium salts and halophilic reagents. 相似文献
4.
van Eis MJ van Der Linde BS de Kanter FJ de Wolf WH Bickelhaupt F 《The Journal of organic chemistry》2000,65(14):4348-4354
In contrast to the terminal phosphinidene complex PhPW(CO)(5) (2), which adds to [5]metacyclophane (1) in a 1,4-fashion, dichlorocarbene preferentially adds in a 1,2-fashion to the formal "anti-Bredt" type double bond of the aromatic ring of 1 to afford the norcaradiene 11b, which immediately rearranges to the bridged cycloheptatriene 12b and further by a [1,5] sigmatropic chlorine migration to the isomeric 13b as the first observable product. More slowly, the latter isomerizes via a dissociative mechanism to give 15b. A computational study supports the notion that the [1,5] chlorine migration in the rearrangement 12b --> 13b, for which an activation barrier of 70.2 kJ mol(-)(1) was calculated, is essentially concerted with minor charge separation. In contrast, the analogous [1,5] chlorine migration in the flat model compound 7,7-dichlorocycloheptatriene (12a) displays features of a dissociative pathway. 相似文献
5.
Acid catalysed epoxy ring opening of several lupane type triterpenoids leads to unusual allylic hydroxylation. The reaction involves the formation of epoxide by m‐chloroperbenzoic acid followed by the treatment of mineral acid. The simple methodology finds utility to introduce a hydroxyl function at the allylic position in these triterpenoids, which is otherwise quite difficult. 相似文献
6.
Alexander S. Orahovats Svetoslav S. Bratovanov Anthony Linden Heinz Heimgartner 《Helvetica chimica acta》1996,79(4):1121-1128
The reaction of 3-(dimethylamino)-2,2-dimethyl-2H-azirine ( 1a ) with 4,5-dihydro-7,8-dimethoxy-1,2-benzothiazepin-3-one 1,1-dioxide ( 4 ) in dioxane at room temperature gave the correspondingly substituted 4H-1,2,5-benzothiadiazecin-6-one 1,1-dioxide 5a in 64% yield (Scheme 2). The structure of this novel ten-membered ring-enlargement product was established by X-ray crystallography (Fig.). Under more vigorous conditions (refluxing dichloroethane), 5a was formed together with the isomeric 6a , both in low yield. The 3-(dimethylamino)-2H-azirines 1b and 1c reacted sluggishly to give the two isomeric ring-enlargement products of type 5 and 6 in yields of 24–29% and 2–4%, respectively (Table 1). Even less reactive is 2,2-dimethyl-3-(N-methyl-N-phenylamino)-2H-azirine ( 1d ), which reacted with 4 in MeCN only at 65°. Under these conditions, besides numerous decomposition products, only traces of 5d and 6d were formed. No ring enlargement was observed with the sterically crowded 1e , which bears an isopropyl group at C(2). 相似文献
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8.
Gy. Keglevich I. Petnehazy L. Tbke 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The forrmation of substituted phosphacycloheptatrienes in ring expansion reaction(s) is describzd. From thc: reac-tion of 3,4-dimethyl-l-phenyl-3-phospholene-l-oxide(1,R1 = c6H5, R2=R3 = CH3) with dichlorocarbene under liquid-liquid phase transfer circumstances not the expected adduct but the appropriate phoshacycloheptatrisne (4, Rl, R2,R3 as above) was prepared. The formation of this product can be explained assuming two ring expansions effected by two series of dichlorocarbene addition and cyclopropane ring opening. In the similar reaction of the methoxy-phospholenc derivative (1, R1=CH3O, R2 = R3 = CH3 four other products are also formed beside the phosphacyclohcptatriene. Again phosphacycloheptatrienes (4) are formed as the result of dichlorocarbene addition to the regioisoners of dihidrophosphorins (2) obtained from the phospholene-dichlorocarbene adducts by thermolysis. The same product can be derived from each regioisomeric pair. 相似文献
9.
At 0° in MeCN, 2,2-disubstituted 3-amino-2H-azirines 1 and 4,4-disubstituted 1,2-thiazetidin-3-one 1,1-dioxides 7 react smoothly to give 1,2,5-thiadiazepin-6-one 1,1-dioxides of type 8 (Scheme 2). The reaction mechanism of this regiospecific ring enlargement to seven-membered heterocycles follows previously described pathways. The structures of 7a and 8b were established by X-ray crystallography (see Figs. 1 and 2). 相似文献
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11.
《合成通讯》2013,43(24):4339-4345
Abstract 1,3-Thiazin-4-ones 9 and 10 have been prepared from the corresponding isothiazolones 7 and 8 by a clean and smooth reaction with tertiary amines at room temperature. This rearrangement is attributed to the abstraction of a methine proton from the 2-position isothiazolone substituent, followed by ring enlargement through cleavage of the S-N bond. 相似文献
12.
José Fernández-Bertrán Luis M. Alfonso Juan C. Alvarez Edilso Reguera 《Journal of inclusion phenomena and macrocyclic chemistry》2000,37(1-4):131-136
The adducts of urea and solid alkyl derivatives can beobtained mechanochemically in good yields. Theproducts synthesized by grinding the solid reagentshave identical IR spectra and XRD powder patterns tothose obtained by crystallization from ethanolicsolutions. 相似文献
13.
《中国化学会会志》2017,64(3):296-302
A facile and highly efficient one‐pot synthesis of novel thiazepine and benzothiazepine derivatives was established by ring expansion. With a greener methodology (ultrasonication), a polysubstituted ring system with the thiazepine core moiety can be easily synthesized from simple and easily available reactants in good yields. Moreover, the synthesized compounds show fluorescence and also antioxidant activity. 相似文献
14.
Base-induced [1,5laroyl migration in the Diels-Alder adduct of [2-(1,3-dioxolan-2-yl)benzoyl]-1, 4-benzoquinone and trans-penta-1, 3-diene followed by acid-mediated cyclisation affords the corresponding hydroxynaphthacenequinone. 相似文献
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16.
Reaction paths for addition of dichlorocarbene to 1,2-disubstituted cyclopropenes were calculated using hybrid density functional theory (B3LYP/6-31G) in the gas phase and in the presence of a continuum solvation model corresponding to acetonitrile. In both the gas phase and acetonitrile, :CCl2-cyclopropene addition follows an asymmetric, non-least-motion approach. Barriers to addition range from 0 to 2 kcal/mol. The reactions proceed in concerted fashion in both the gas phase and solution to yield 1,3-dienes or bicyclobutanes. The reaction pathway on this complex potential energy surface of this reaction appears to bifurcate, and the product distribution is believed to be controlled by reaction dynamics. At the present level of theory, there appears to be no minimum on the potential energy surface corresponding to a dipolar intermediate. 相似文献
17.
Sheng Tao Dr. Qingqing Bu Qianqian Shi Prof. Dr. Donghui Wei Prof. Dr. Bin Dai Dr. Ning Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(15):3252-3258
Pyrido-benzodiazepine derivatives are undoubtedly one of the most important structural motifs in the marketed drugs and the drug candidates. Commonly synthetic methods for construction of the benzodiazepine ring derivatives are based on the condensation reactions of two highly functionalized synthons. The development of synthesis for these compounds, however, is hampered by the regioselectivity and atom economy. In this work, a one-step synthesis of pyrido-benzodiazepine backbones and its analogues is achieved through continuous ring-opening hydrolysis of benzimidazole salts and intramolecular C−H bond activation. The reaction mechanism is explored by control experiments and density functional theory (DFT) calculations. 相似文献
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Prof. Dr. Klaus Banert Dr. Madhu Chityala Dr. Marcus Korb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6158-6164
Although the chemistry of elusive tricyanomethane (cyanoform) has been studied during a period of more than 150 years, this compound has very rarely been utilized in the synthesis or modification of heterocycles. Three-membered heterocycles, such as epoxides, thiirane, aziridines, or 2H-azirines, are now treated with tricyanomethane, which is generated in situ by heating azidomethylidene-malonodinitrile in tetrahydrofuran at 45 °C or by adding sulfuric acid to potassium tricyanomethanide. This leads to ring expansion with formation of 2-(dicyanomethylidene)oxazolidine derivatives or creation of the corresponding thiazolidine, imidazolidine, or imidazoline compounds and opens up a new access to these push–pull-substituted olefinic products. The regio- and stereochemistry of the ring-enlargement processes are discussed, and the proposed reaction mechanisms were confirmed by using 15N-labeled substrates. It turns out that different mechanisms are operating; however, tricyanomethanide is always acting as a nitrogen-centered nucleophile, which is quite unusual if compared to other reactions of this species. 相似文献