Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• , only the starting material could be reisolated. Encouraged by these findings we attempted to perform the [3,3]-sigmatropic rearrangement with C1-substituted A rings, as many B-seco limonoids are oxygenated at this position. For this purpose, both the anti- and syn-substituted β-alkoxy esters 56 and 57

• were synthesized (Scheme 7; for experimental procedure see Supporting Information File 1). In the literature [50] not many examples are known in which β-alkoxy esters serve as rearrangement precursors as the β-elimination of the alkoxy group can easily occur under the rearrangement conditions. Indeed

• revealed that the main product is 1S-configurated as in most B-seco limonoids suggesting that an equatorial attack of the hydride is slightly preferred over the axial attack. However bearing in mind the elimination issues with β-alkoxy esters during Ireland–Claisen rearrangements discussed above we decided

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• by a Rupe rearrangement [190] using refluxing acetic acid as solvent to give ketone 220. Addition of deprotonated ketone 220 onto acryloylsilane 221 [191] gave alkoxy intermediate 222, which underwent a Brook rearrangement followed by cyclopropane formation to yield anionic 223 in situ [192]. The

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• peroxide functional group. As in the above-considered studies, the intramolecular cyclization of ozonolysis products can be performed with the use of the hydroperoxide group provided that there is an appropriate electrophilic center. The reaction of oxetanes 60a,b with ozone in methanol produced 3-alkoxy

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• carbene complex B [35] as precatalysts (Table 1). Phosphine-free precatalysts with a hemilabile alkoxy ligand are supposed to be well-suited for cross metathesis reactions [36][37]. With a moderate catalyst loading of 2.0 mol % of A, we isolated the expected cross metathesis product 11 in an acceptable

One-pot sequential synthesis of isocyanates and urea derivatives via a microwave-assisted Staudinger–aza-Wittig reaction

• Diego Carnaroglio,
• Katia Martina,
• Giovanni Palmisano,
• Andrea Penoni,
• Claudia Domini and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2013, 9, 2378–2386, doi:10.3762/bjoc.9.274

• . This synthetic protocol is versatile and highly efficient with both primary and secondary azido derivatives as well as alkoxy and amido groups. The one-pot, two-step procedure afforded urea derivatives in high yield and purity via the isocyanate intermediate. To broaden the scope of the study, the

Gold(I)-catalyzed 6-endo hydroxycyclization of 7-substituted-1,6-enynes

• Ana M. Sanjuán,
• Alberto Martínez,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2013, 9, 2242–2249, doi:10.3762/bjoc.9.263

• external nucleophiles undergo skeletal rearrangements to afford products such as III (single cleavage) [14]. However, reactions of II with alcohols or water give the corresponding products of alkoxy(hydroxy)cyclization IV [15][16][17] (Scheme 1). The less common 6-endo cyclization via metal carbenes V was

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• group has a small accelerative effect and alkoxy groups a larger accelerative effect when located at the C(VI) site of the allyl vinyl ether [3][23]. These observations were attributed to an electronic effect whereby the C(VI)-substituent weakened the O–C(IV) bond and hence the rearrangement energy

Gold-catalyzed intermolecular coupling of sulfonylacetylene with allyl ethers: [3,3]- and [1,3]-rearrangements

• Jungho Jun,
• Hyu-Suk Yeom,
• Jun-Hyun An and
• Seunghoon Shin

Beilstein J. Org. Chem. 2013, 9, 1724–1729, doi:10.3762/bjoc.9.198

• not undergo O-attack on the alkyne in the presence of Ag-catalyst [7]. With the above optimized conditions in hand, the scope of the carboalkoxylation of sulfonylacetylene was examined (Table 2). The alkoxy group in the ethers 2 had an impact on the efficiency of the current tandem carboalkoxylation

• . The reaction of methyl ether 2a was accompanied by a side product 4 (R1 = Me) resulting from a premature dissociation of the allyl cation fragment before the rearrangement, decreasing the yield of desired 3a (Table 2, entry 1). However, 2b having sterically bulky secondary (IPr) or primary alkoxy

Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

• Daisuke Hirose and
• Tsuyoshi Taniguchi

Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196

• molecular oxygen, an alkoxy radical 26 is formed from the peroxynitrite intermediate (ROONO) generated by the reaction of the peroxy radical (ROO•) intermediate with t-BuONO. The alkoxy radical causes an 1,5-hydrogen shift to give the corresponding alkyl radical 27 followed by formation of another alkoxy

• radical 28 through a similar process. An important issue in the current work is the effect of water to determine the destiny of 28. In the absence of water, the alkoxy radical 28 was merely oxidized to aldehyde 29, which was converted into γ-lactol 2 [21]. On the other hand, if 28 is caught by NO2 more

Re₂O₇-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

• Wantanee Sittiwong,
• Michael W. Richardson,
• Charles E. Schiaffo,
• Thomas J. Fisher and
• Patrick H. Dussault

Beilstein J. Org. Chem. 2013, 9, 1526–1532, doi:10.3762/bjoc.9.174

• ], we needed to prepare a number of 3-alkoxy-1,2-dioxolanes. Brønsted acid-promoted etherification of hemiacetals (1,2-dioxolan-3-ols) required harsh conditions and proceeded in good yields only for unhindered alcohols [18]. We were curious whether Re2O7, a catalyst known to activate alcohols via a

An organocatalytic route to 2-heteroarylmethylene decorated N-arylpyrroles

• Alexandre Jean,
• Jérôme Blanchet,
• Jacques Rouden,
• Jacques Maddaluno and
• Michaël De Paolis

Beilstein J. Org. Chem. 2013, 9, 1480–1486, doi:10.3762/bjoc.9.168

• TFA to promote the cyclization into pyrrolidines 4i,j which upon treatment with DBU were converted into pyrroles 5i,j in 41% and 52% overall yields. While p-alkoxy substituted (R = OAllyl, OBn) anilines are compatible, the methodology proved troublesome with o-alkoxy substituted anilines, the main

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• . Photophysical properties The spectroscopic properties of 1,8-naphthalimides are strongly dependent on the substituent at C-4 of the naphthalene ring. In general, the derivatives with a halogen atom or alkoxy groups are colorless and exhibit blue fluorecence [15][16], while the amino-substituted 1,8

Copper-catalyzed aerobic aliphatic C–H oxygenation with hydroperoxides

• Pei Chui Too,
• Ya Lin Tnay and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2013, 9, 1217–1225, doi:10.3762/bjoc.9.138

• 3% yields, respectively, via the desired 1,4-dioxygenation, while benzophenone (7b) was also formed in 30% yield through fragmentation of the transient alkoxy radical (Scheme 4). Use of 40 mol % of NHPI slightly improved the yields of 1,4-dioxygenation products 2i and 3i (40% and 4% yields

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

• categorized as Type-1 diradicals [1][27], which possess a π-single-bonding character (–π–, closed-shell character) between the two radical sites. The role of the alkoxy group (OR) on the lifetime (k = 1/τ) was investigated by combined studies of experiments and quantum chemical calculations [26][28]. The

• steric repulsion between the alkoxy group and the phenyl ring, which is indicated in the transition-state structure for the ring-closing reaction (Scheme 1), was found to play an important role in determining the energy barrier of the ring-closing process, τ293 = 292 ns (DRa: OR = OCH3, λmax = 574 nm

• . Localized singlet diradicals. (a) Absorption spectrum of the singlet diradical DRe in a MTHF matrix at 80 K; (b) transient absorption spectrum of AZe measured immediately after the laser pulse (λexc = 355 nm); (c) transient decay trace at 580 nm and 20 °C. Alkoxy group effect on the lifetime of π-single

Diastereoselective synthesis of nitroso acetals from (S,E)-γ-aminated nitroalkenes via multicomponent [4 + 2]/[3 + 2] cycloadditions promoted by LiCl or LiClO₄

• Leandro Lara de Carvalho,
• Robert Alan Burrow and
• Vera Lúcia Patrocinio Pereira

Beilstein J. Org. Chem. 2013, 9, 838–845, doi:10.3762/bjoc.9.96

• tendency to the pseudoaxial orientation of the alkoxy group in nitroso acetals is associated with a stabilization generated by an anomeric effect [1][36]. The protons (H6) and (H4) were both irradiated in 2D NOESY experiments and a cis relationship between them was achieved for all cycloadducts. When the

• [3 + 2] cycloadditions, we believe that in the TS the respective nitronates present a half-chair conformation with the HC(4) substituent and the alkoxy group in an axial position to maximize the stabilization generated by the anomeric effect [9][33][41][42]. Thus, the competitive endo/exo approach of

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• process; it also quenches the intermediate alkoxy radical, liberating concomitantly an ethyl radical to propagate the chain. Except in the cleavage of epoxides, homolytic rupture of carbon–oxygen bonds is generally a difficult process. Radicals can thus be generated next to alcohols or esters without fear

Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

• Alexej Bubnov,
• Miroslav Kašpar,
• Věra Hamplová,
• Ute Dawin and
• Frank Giesselmann

Beilstein J. Org. Chem. 2013, 9, 425–436, doi:10.3762/bjoc.9.45

• observed for the chiral compound in [26] having the same molecular core as TL4 but a branched chiral alkoxy chain instead of the decyloxy group used for TL4. The relation between the molecular structure and mesomorphic properties of these new multifunctional compounds with different structures is discussed

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

Radical zinc-atom-transfer-based carbozincation of haloalkynes with dialkylzincs

• Fabrice Chemla,
• Florian Dulong,
• Franck Ferreira and
• Alejandro Pérez-Luna

Beilstein J. Org. Chem. 2013, 9, 236–245, doi:10.3762/bjoc.9.28

• plausible explanation for the fact that bromine substitution occurs from α-oxgenated bromoalkyne 11 and not from 9. Regarding our 1,4 addition/carbocyclization sequence, these test experiments provide two important pieces of evidence for the behavior of 3a in the presence of a dialkylzinc. First, β-alkoxy

A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

• Kalpana Upadhyaya,
• Venkatesh Gude,
• Golam Mohiuddin and
• Rao V. S. Nandiraju

Beilstein J. Org. Chem. 2013, 9, 26–35, doi:10.3762/bjoc.9.4

• , i.e.., chloro in the bent or transverse direction in the central core and cyano in the lateral direction at one terminal end of the molecule, are designed and synthesized. These molecules possess an alkoxy chain attached at only one end of the bent-core molecule. The molecular structure

• Discussion Synthesis and characterization Here we adopted a very simple and straightforward synthetic methodology for the synthesis of these materials exhibiting a nematic phase. The non-symmetric four-ring molecules possess an alkoxy chain attached at only one end of the bent-core molecule, while the other

Synthesis of spiro[dihydropyridine-oxindoles] via three-component reaction of arylamine, isatin and cyclopentane-1,3-dione

• Yan Sun,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 8–14, doi:10.3762/bjoc.9.2

• Table 1. From these results we could see that only anilines with electron-donating alkyl and alkoxy groups reacted smoothly. When anilines with electron-withdrawing p-chloro, p-bromo, m-nitro, or p-nitro groups were used in this three-component reaction, no expected spiro[dihydropyridine-oxindole] could

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

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

• -azobenzene derivatives. This notable red-shift of the absorption wavelength arises from the strong charge transfer from the alkoxy group to the positively-charged nitrogen atom of the pyridinium salt. Figure 8 shows the transient absorption generated upon pulsed laser irradiation of ethanol solutions of azo

• electron transfer from the alkoxy group to the pyridinium salt produces a partial breaking of the double N–N bond of the azo moiety, thereby facilitating the rotation around this bond to recover the more stable initial trans configuration in a quick fashion [56]. Type-II azoderivatives: photochromic

• the alkoxy- and hydroxy-substituted azo-dyes reflect that some alteration in their intimate isomerisation mechanism occurs. The rapid thermal cis-to-trans isomerisation of the hydroxy-substituted azo-dyes suggests that their back reaction takes place via the rotational pathway, through a polar

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

• , alkoxy and alkylsulfanyl groups. Here we demonstrate an efficient method for the preparation of several hydrophobic di- and tri-substituted phenylhydrazines in purities sufficient for further chemical transformations. Finally, we demonstrate the application of one of the phenylhydrazines for the

• ± 0.01 eV. Conclusion We have developed a synthetic protocol for the efficient preparation of electron-rich phenylhydrazines 1 substituted with alkylsulfanyl, alkyl and alkoxy groups from Boc hydrazides 2. Experiments demonstrate that the addition of hydrazides 2 to a large excess of TfOH (5 equiv) at

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• ][81], push–pull amines and betaines 74–78 [82][83][84][85][86][87], alkoxy derivatives 79,80 [88], biimidazoles 81 [89][90][91][92], and triimidazoles 82 [93][94], as well as fullerenes [95] and polymers [96][97][98][99]. The chemistry of 4,5-dicyanoimidazole was reviewed in 1987 by Donald and Webster