Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

• Jianhuai Ye,
• Yoshihisa Fujiwara and
• Manabu Abe

Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

• , CH), 105.90 (d, CH), 133.44 (s, C), 161.54 (s, COCH3); ESIMS (m/z): [M + Na]+ calcd for C18H20O4N4, 379.13768; found, 379.13776. 5,5-Dimethyl-2,2-bis(3,5-dimethoxybenzyl)-Δ3-1,3,4-oxadiazoline (2f). A solution of (3,5-dimethoxybenzyloxycarbonyl)hydrazone of acetone (1.30 g, 4.87 mmol) in CH2Cl2 (5 mL

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• substitution (type-I), that is, bearing a push–pull configuration. Secondly, kinetic studies of different azophenolic systems (type-II) will be presented, since these azoderivatives exhibit a fast thermal back reaction due to their capability to establish an azo-hydrazone tautomeric equilibrium. Both type-I

• switches acting within the milliseconds time scale, based on chromophores able to establish azo-hydrazone tautomeric equilibria Hydroxy-substituted azobenzenes are a very interesting family of rapidly thermally isomerising azoderivatives, which have been applied successfully not only for light-driven

• molecules control the rate of the isomerisation process for type-II azoderivatives. The formation of intermolecular hydrogen bonds between the nitrogen atom of the azo group and the solvent proton, as well as between the OH group of the azo-dye and the solvent, favours a hydrazone-like electronic

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

• new method introduced to secure facile access to complex architectures. Chemoorthogonal to the ring-opening disulfide exchange used for SOSIP, hydrazone exchange is then introduced to achieve stack exchange, which is a “switching” technology invented to drill giant holes into SOSIP architectures and

• fill them with functional π-stacks of free choice. Keywords: asparagusic acid; charge-transfer cascades; chromophores; disulfide exchange; hydrazone exchange; molecular switches; naphthalenediimides; π-stacks; surface-initiated polymerization; Introduction The architecture of photosystem 1 is rather

• acid 28. Hydrazide deprotection in NDI 29 and in situ hydrazone formation with benzaldehyde 30 gave propagator 3. In contrast to propagator 3, propagator 4 is constructed around a yellow, core-substituted cNDI fluorophore. Nevertheless, the synthesis of this target molecule also starts with NDA 13

The importance of the rotor in hydrazone-based molecular switches

• Xin Su,
• Timo Lessing and
• Ivan Aprahamian

Beilstein J. Org. Chem. 2012, 8, 872–876, doi:10.3762/bjoc.8.98

• of a series of hydrazone-based systems having different functional groups as part of the rotor (R = COMe, CN, Me, H), was studied. The switching efficiency of these systems was compared to that of a hydrazone-based molecular switch (R = COOEt) whose E/Z isomerization is fully reversible. It was found

• isomerization; hydrazone; molecular switches; pH activation; structure–property analysis; Findings Nature is full of elegant examples of perfectly designed biological motors and machines [1] that perform delicate and precise tasks. Primitive as they may be, numerous artificial molecular machines [2][3][4][5][6

• -based light-driven rotary switches that can be induced to rotate at different rates by replacing a naphthyl group in the upper-half of the molecule (i.e., the rotor) with a less sterically hindered benzothiophenyl group [20]. Previously, we have shown that hydrazone-based rotary switches can change

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

• of 10a showing the potential to produce terminally as well as internally oxidised and modified poly-LacNAc oligomers (11a). A: Labelling of poly-LacNAc oligomers 3a–c and 9a with biotin hydrazide derivative BACH (12) yielding the hydrazone products (13a–c and 14a); 13a–c and 14a were subsequently

Chemistry of polyhalogenated nitrobutadienes, 10: Synthesis of highly functionalized heterocycles with a rigid 6-amino-3-azabicyclo[3.1.0]hexane moiety

• Viktor A. Zapol’skii,
• Jan C. Namyslo,
• Armin de Meijere and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2012, 8, 621–628, doi:10.3762/bjoc.8.69

• starting materials for biologically active compounds. Pharmaceuticals bearing an azabicyclo[3.1.0]hexane unit. Stabilizing hydrogen bond in nitrobutadiene-derived imidacloprid analogues 9–12. Conceivable tautomeric structures of 16. Synthesis of the azabicyclic hydrazone 6. Novel imidacloprid analogues 11

Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

• Aurélie Dos Santos,
• Laurent El Kaim,
• Laurence Grimaud and
• Caroline Ronsseray

Beilstein J. Org. Chem. 2011, 7, 1310–1314, doi:10.3762/bjoc.7.153

• Pyrazolidinones were prepared in a two-step sequence starting from α-hydrazonocarboxylic acids. After a four-component Ugi coupling, the resulting hydrazone was engaged in a copper triggered [3 + 2] cycloaddition/aerobic oxidation cascade. Keywords: aerobic oxidation; copper(II); [3 + 2] cycloaddition; hydrazone

• pyrazolidinone under oxidative conditions from simple hydrazone derivatives (Scheme 1) [13]. The cascade features a [3 + 2] cycloaddition coupled with an aerobic oxidation of the resulting pyrazolidine. A further oxidative coupling may be observed according to the substitution pattern of the starting acyl

• possible Ugi pathways to introduce an alkene moiety that is prone to undergo an intramolecular [3 + 2] cycloaddition with a hydrazone, we selected the Ugi coupling between α-hydrazonocarboxylic acids and allylamine as the most straightforward path. There are several reports on the use of hydrazones in Ugi

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• indole synthesis a hydrazine, which is most commonly derived from the corresponding diazonium salt, is reacted with a suitable carbonyl compound. Alternatively, the Japp–Klingemann reaction can be used to directly couple the diazonium salt with a β-ketoester to obtain a hydrazone which can then undergo

• intermediate for carvedilol is 4-hydroxy-9H-carbazole (141) [42]. In analogy to the Fischer indole synthesis, cyclohexane-1,3-dione monophenyl hydrazone 139 is prepared via condensation of phenylhydrazine (138) with 1,3-cyclohexanedione (121, Scheme 29). This compound can then undergo an acid catalysed Fischer

Approaches towards the synthesis of 5-aminopyrazoles

• Ranjana Aggarwal,
• Vinod Kumar,
• Rajiv Kumar and
• Shiv P. Singh

Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25

• reaction of trifluoroacetylbenzyl cyanide 4 with heteroarylhydrazines [32]. The reaction of 2-hydrazino-4-methylquinoline with α-trifluoroacetylbenzyl cyanide (R = CF3) (4) at room temperature afforded the intermediate hydrazone 5. The hydrazone 5 was characterized by IR and NMR spectroscopy. The IR

• spectrum of 5 showed a fundamental stretching band due to C≡N at 2179 cm−1. The 19F NMR spectrum of compound 5 showed fluorine signal at δ −65 ppm due to CF3 group confirming the formation of hydrazone 5, which exists as the Z-isomer. From the literature [33], the signal for the CF3 group in

• -oxotetrahydrothiophene (18) in refluxing ethanol gave the thienopyrazoles in excellent yields. The regioselectivity of this process has been confirmed by the treatment of 18 with phenylhydrazine, which generated a mixture of intermediate hydrazone 20 and 2-phenyl-3-aminothieno[3,4-c]pyrazole (21) (Scheme 6). Hydrazones

Synthesis of some novel hydrazono acyclic nucleoside analogues

• Mohammad N. Soltani Rad,
• Ali Khalafi-Nezhad and
• Somayeh Behrouz

Beilstein J. Org. Chem. 2010, 6, No. 49, doi:10.3762/bjoc.6.49

• Abstract The syntheses of novel hydrazono acyclic nucleosides similar to miconazole scaffolds are described. In this series of acyclic nucleosides, pyrimidine as well as purine and other azole derivatives replaced the imidazole function in miconazole and the ether group was replaced with a hydrazone moiety

• using phenylhydrazine. To interpret the dominant formation of (E)-hydrazone derivatives rather than (Z)-isomers, PM3 semiempirical quantum mechanic calculations were carried out which indicated that the (E)-isomers had the lower heats of formation. Keywords: acyclic nucleoside; chemotherapeutic agent

• ; hydrazone; ketone; miconazole; Introduction In recent years, fungal infections have become an important complication and a major cause of morbidity and mortality in immune-compromised individuals who suffer from tuberculosis, cancer or AIDS, and who undergo organ transplants [1][2]. Up to now, there has

Synthesis of thienyl analogues of PCBM and investigation of morphology of mixtures in P3HT

• Fukashi Matsumoto,
• Kazuyuki Moriwaki,
• Yuko Takao and
• Toshinobu Ohno

Beilstein J. Org. Chem. 2008, 4, No. 33, doi:10.3762/bjoc.4.33

• chloroform as an eluent and the compounds 1a and 1b were easily obtained. Then, the carbonyl group of 1 was converted to hydrazone by mixing 1 with p-toluenesulfonyl hydrazide. The compounds 2 were obtained as white to pale yellow solids in good yields (2a; 85%, 2b; 90%, 2c; 74%, 2d; 70%). The

• shifts of bridging units. It is well known that [5,6]fulleroid has low solubility and is thermodynamically unstable; hence, it cannot be used in a photovoltaic device. However, except for 2b, the thienyl-substituted hydrazones 2a, 2c, and 2d yielded only [6,6]methanofullerenes. The hydrazone 2b yielded a

One-pot synthesis of novel 1H-pyrimido[4,5-c][1,2]diazepines and pyrazolo[3,4-d]pyrimidines

• Dipak Prajapati,
• Partha P. Baruah,
• Baikuntha J. Gogoi and
• Jagir S. Sandhu

Beilstein J. Org. Chem. 2006, 2, No. 5, doi:10.1186/1860-5397-2-5

• hot acid produces pyrazolo [3,4-d]pyrimidines, most likely by hydrolytic ring opening at the 'hydrazone' bond followed by a retro-aldol reaction and ring closure.[25][33][34] In contrast, we synthesised the corresponding pyrazolo [3,4-d]pyrimidines in high yields under mild conditions without heating