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71.
A mild, simple, and efficient synthetic procedure for the preparation of 2-monobromo-, 2,7-dibromo-, and 2,2′,7,7′-tetrabromo-substituted spirobifluorene derivatives and their key intermediates, 2-monobromo- and 2,7-dibromo-substituted fluorene compounds, has been developed. The oxidative bromination of fluorene and spirobifluorene was achieved using NaBr/H2O2 as the bromine source. High conversion of the starting materials was achieved together with good selectivities under optimized reaction conditions. 相似文献
72.
Previous reports in the literature have suggested that concerted transition states for oxidative addition would not exist in solution. By contrast, this report describes the successful location of transition states for the oxidative addition of monoligated Pd(PtBu3), bisligated Pd(PtBu3)(MeCN), and anionic Pd(PtBu3)F? complexes to C–Cl and C–OTf of an aryl chloro triflate in polar solvent (MeCN). Optimizations were done with implicit solvation and a combined implicit/explicit solvation approach in which six acetonitrile molecules were additionally involved in the optimization. The geometries obtained from optimizations employing an implicit solvation model are structurally largely analogous to those found using a combination of implicit and explicit solvation. 相似文献
73.
Stereoselective route to tricyclo[5.3.1.01,5]undecane and bicyclo[4.2.0]octane ring systems present in the molecular structure of tricycloillicinone, cedrenoids and endiandric acid, elysiapyrones, respectively, is described. A tandem oxidative dearomatization of o-hydroxymethylphenol, π4s+π2s cycloaddition, reactivity modulation in excited state and ring-closing metathesis are the key features of our approach. 相似文献
74.
A novel and efficient protocol for the synthesis of α,β-unsaturated amides has been developed using catalytic amount of Cu(OAc)2 and TBHP as an available oxidant. Oxidative coupling of various unsaturated carboxylic acids with N,N-disubstituted formamides was examined to furnish the desired products in good yields. 相似文献
75.
Gan Wang Clint A. JamesNicholas A. Meanwell Lawrence G. HamannMakonen Belema 《Tetrahedron letters》2013
A stereoselective and scalable synthesis of (1R,3S,5R)-2-(tert-butoxycarbonyl)-2-azabicyclo[3.1.0]hexane-3-carboxylic acid (3a) is described. Key to the success of the devised route was the realization that the stereoselectivity of a cyclopropanation step could be controlled by the composition of the functional group at C-α. 相似文献
76.
A one-pot approach to indolo[2,1-b]quinazolines from indole-3-carbaldehydes through the Dakin oxidation was developed. It was shown that the reaction proceeded through the condensation of indole-3-carbaldehydes with isatoic anhydrides, derived in situ from indole-3-carbaldehydes by the Dakin oxidation, and further oxidation/cyclization steps. 相似文献
77.
A series of 4-spiro-cyclohexadienonyl-β-lactam-3-carbonitriles, 2,7-dioxo-1-azaspiro[3.5]nona-5,8-diene-3-carbonitriles, was synthesized in satisfactory to excellent yields via the intramolecular nucleophilic cyclization of N-(p-hydroxyphenyl)cyanoacetamides with iodobenzene diacetate (IBD) as oxidant and potassium hydroxide as base. Acetic 4-spiro-cyclohexadienonyl-β-lactam-3-carbimidic anhydrides were obtained when organic base triethylamine was applied instead of potassium hydroxide. The mechanisms of the intramolecular nucleophilic cyclization and formation of acetic β-lactam-3-carbimidic anhydrides were proposed. The cyclization is a sequence of nucleophilic ipso addition and oxidative dearomatization. The formation of acetic carbimidic anhydrides is an acid-catalyzed acetate addition to the nitriles. 相似文献
78.
A novel triphenylamine based oxidative chemosensor TOC was synthesized. The chromogenic and fluorogenic behaviors of TOC towards Hg2+ and Cu2+ ions in a binary mixture of MeCN/H2O (9/1) were dramatically different. TOC displays colorimetric ‘naked eye’ recognition of Hg2+ and fluorogenic ‘turn on’ response towards Cu2+ via a unique cyclization reaction using two different detection modes. Moreover, TOCAZOL obtained from the oxidative cyclization reaction of TOC with Cu(ClO4)2 can be used as a selective fluorescent sensor toward Hg2+ ion. 相似文献
79.
Honglin Li Fengyu Liu Yi Xiao Perry J. Pellechia Mark D. Smith Xuhong Qian Guiren Wang Qian Wang 《Tetrahedron》2014
We have revisited the synthesis of a series of ICT fluorophores, which were reported to have a core structure of 8-oxo-8H-acenaphtho[1,2-b]pyrrol-9-carbonitrile. However, based on the 2D NMR and X-ray diffraction analysis, their core structure was corrected as 1-oxo-1H-phenalene-2,3-dicarbonitrile (1). Compound 1 shows a highly electron-deficient nature and can easily undergo oxidative SNArH reaction on the naphthyl ring to produce a series of novel ICT fluorophores. The regioselectivity of this substitution reaction was studied by introduction of representative nucleophiles. Moreover, due to the strong rigidity and efficient ICT nature, the obtained fluorescent dyes display very good spectroscopic properties even in an aqueous environment. 相似文献
80.
Several 8-8-coupled tetraarylfuran-type oligostilbenes were prepared through FeCl3·6H2O-catalyzed regioselective oxidative couplings of protected resveratrol precursors. The global deprotection of the coupling dimers in a one-pot reaction yielded (±)-pallidol instead of the targets (±)-restrytisol B and (±)-tricuspidatol A. 相似文献