Synthesis of 2-trifluoromethylpyrazolo[5,1-a]isoquinolines via silver triflate-catalyzed or electrophile-mediated one-pot tandem reaction

• Xiaoli Zhou,
• Meiling Liu,
• Puying Luo,
• Yingjun Lai,
• Tangtao Yang and
• Qiuping Ding

Beilstein J. Org. Chem. 2014, 10, 2286–2292, doi:10.3762/bjoc.10.238

• Gynecology, Jiangxi Provincial people's Hospital, Nanchang, Jiangxi 330006, P. R. China 10.3762/bjoc.10.238 Abstract An efficient one-pot tandem cyclization/[3 + 2] cycloaddition reaction of N’-(2-alkynylbenzylidene)hydrazides with ethyl 4,4,4-trifluorobut-2-ynoate under silver triflate-catalyzed or

• annulation of N’-(2-alkynylbenzylidene)hydrazides followed by an 1,3-dipolar cycloaddition. Results and Discussion Based on Wu’s work on the silver triflate-catalyzed tandem reaction of N’-(2-alkynylbenzylidene)hydrazides with dimethyl acetylenedicarboxylate [28], we started our research by examining the

• reaction of N’-(2-alkynylbenzylidene)hydrazides 1a (0.3 mmol) and ethyl 4,4,4-trifluorobut-2-ynoate (2, 0.6 mmol) using NaOAc (0.45 mmol) as base, in the presence of AgOTf (5 mol %) and 4 Å MS (75 mg) in CH2Cl2 (3 mL) at room temperature overnight. Surprisingly, the unexpected [3 + 2] cycloaddition product

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• new key intermediates encompass the structural motif C=N+–N−, a very useful framework for further functionalizations. Wu and co-workers widely used preformed N’-(2-alkynylbenzylidene)hydrazides 42 in two component reactions involving 43 as an intermediate for the construction of N-heterocycles

• . Moreover, in the field of MCRs, in 2010 the same authors assembled a small library of 2-amino-1,2-dihydroisoquinolines 47 starting from N’-(2-alkynylbenzylidene)hydrazides 42, methanol and α,β-unsaturated aldehydes 44. The three-component process is co-catalyzed by silver triflate and an N-heterocyclic

• . Concurrently, the released N-heterocyclic carbene would re-enter the catalytic cycle. Nevertheless, the reaction suffers from severe limitation on the nature of the R1 group attached to the triple bond of N′-(2-alkynylbenzylidene)hydrazides 42 and only aryl groups proofed to be effective. Broadening the scope

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• ion furnishes a new amine radical cation 152. Finally, amine radical cation 152 is reduced by Ru(I) to provide the annulation product 153 and regenerate Ru(II), thus completing the catalytic cycle. Our group also realized cleavage of N–N bonds by irradiation of aromatic hydrazines or hydrazides in the

• presence of Ru(bpz)3(PF6)2 and air (Scheme 34) [108]. A 13 W compact fluorescent light was sufficient as the light source. N,N-disubstituted hydrazines and hydrazides were suitable substrates provided that at least one of the two substituents on the nitrogen atom was an aryl group. Electron-richer

• hydrazines were found to be more reactive than hydrazides. This is consistent with our expectation that, similar to amines, hydrazines and hydrazides act as an electron donor to reductively quench the photoexcited Ru(II) complex. The photoexcited state of Ru(bpz)3 (E1/2*II/I = 1.45 V vs SCE) is more

Regioselective synthesis of 7,8-dihydroimidazo[5,1-c][1,2,4]triazine-3,6(2H,4H)-dione derivatives: A new drug-like heterocyclic scaffold

• Nikolay T. Tzvetkov,
• Harald Euler and
• Christa E. Müller

Beilstein J. Org. Chem. 2012, 8, 1584–1593, doi:10.3762/bjoc.8.181

• introduced. The synthetic strategy allows broad structural variation of this new drug-like heterobicyclic scaffold. In addition to extensive NMR and MS analyses, the structure of one derivative was confirmed by X-ray crystallography. Keywords: hydantoins; hydrazides; imidazotriazines; N-alkylation; regio

• main challenge in the synthesis of 23–25 was the construction of the 1,2,4-triazine ring. Direct reaction of 13–15 with hydrazine hydrate failed, and only the corresponding hydrazides were formed. Therefore, the C5 carbonyl group of 13–15 was regioselectively thionated with phosphorus pentasulfide in

Multistep organic synthesis of modular photosystems

• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2012, 8, 897–904, doi:10.3762/bjoc.8.102

• 21. After chemoselective, acid-catalyzed deprotection, the liberated amines were coupled with the Boc-protected cysteine tert-butyl disulfide 22. The obtained amide 23 was treated with TFA for Boc removal and coupled with the geminal diphosphonate foot 7. Deprotection of both hydrazides and

Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc) oligomers and N,N-diacetyllactosamine (LacDiNAc) based on galactose oxidase treatment

• Christiane E. Kupper,
• Ruben R. Rosencrantz,
• Birgit Henßen,
• Helena Pelantová,
• Stephan Thönes,
• Anna Drozdová,
• Vladimir Křen and
• Lothar Elling

Beilstein J. Org. Chem. 2012, 8, 712–725, doi:10.3762/bjoc.8.80

• up. Incorporation of the aldehyde group gives rise to further modification with different amines, hydroxylamines, and hydrazides. Thereby modifications that introduce various chemical properties can be incorporated and tested for their influence on protein binding and biological function. The

Synthesis of oleophilic electron-rich phenylhydrazines

• Aleksandra Jankowiak and
• Piotr Kaszyński

Beilstein J. Org. Chem. 2012, 8, 275–282, doi:10.3762/bjoc.8.29

• alkyl, alkoxy or alkylsulfanyl groups were successfully prepared by acid-induced removal of the Boc group in hydrazides 2. The reaction is carried out with 5 equivalents of TfOH in CF3CH2OH/CH2Cl2 at −40 °C for 1.5 min. Under these conditions, the deprotected hydrazine 1 is fully protonated, which

• increases its stability in the reaction medium. The hydrazines were isolated in 60–86% yields and purities >90%. The hydrazides 2 were obtained in 43–71% yields from aryl bromides 5, which were lithiated with t-BuLi and subsequently reacted with di-tert-butyl azodicarboxylate (DTBAD). Keywords

• deprotection of hydrazides II have been developed (Figure 1). Hydrazides II are efficiently obtained by the addition of organometallic reagents III, prepared from aryl halide IV, to azodicarboxylate diesters (AD) [16][17]. Alternatively, II can be obtained in the Pd(0)- or Cu2+-catalyzed reaction of

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32