- Efficient and convenient synthesis of 3,4,5-trimethoxybenzaldehyde from p-cresol
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With p-cresol as starting material, 3,4,5-trimethoxybenzaldehyde was synthesized in an overall yield of 67.4% via bromination, hydrolysis, methoxylation and methylation.
- Ji, Ya-Fei,Zong, Zhi-Min,Wei, Xian-Yong
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- Ni-NiO heterojunctions: a versatile nanocatalyst for regioselective halogenation and oxidative esterification of aromatics
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Herein, we report a facile method for the synthesis of Ni-NiO heterojunction nanoparticles, which we utilized for the nuclear halogenation reaction of phenol and substituted phenols usingN-bromosuccinimide (NBS). A remarkablepara-selectivity was achieved for the halogenated products under semi-aqueous conditions. Interestingly, blocking of thepara-position of phenol offeredortho-selective halogenation. In addition, the Ni-NiO nanoparticles catalyzed the oxidative esterification of carbonyl compounds with alcohol, diol or dithiol in the presence of a catalytic amount of NBS. It was observed that the aromatic carbonyls substituted with an electron-donating group favoured nuclear halogenation, whereas an electron-withdrawing group substitution in carbonyl compounds facilitated the oxidation reaction. In addition, the catalyst was magnetically separated and recycled 10 times. The tuned electronic structure at the Ni-NiO heterojunction controlled selectivity and activity as no suchpara-selectivity was observed with commercially available NiO or Ni nanoparticles.
- Bhardwaj, Nivedita,Goel, Bharat,Indra, Arindam,Jain, Shreyans K.,Singh, Ajit Kumar,Tripathi, Nancy
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p. 14177 - 14183
(2021/08/16)
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- Magnetic nano-structured cobalt-cobalt oxide/nitrogen-doped carbon material as an efficient catalyst for aerobic oxidation of p-cresols
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Efficient aerobic oxidation has been developed for the selective preparation of a sequence of valuable p-hydroxybenzaldehydes from corresponding p-cresols, using a new magnetically separable catalyst of nano-structured cobalt-cobalt oxide/nitrogen-doped carbon (CoOx@CN) material. CoOx@CN showed high activity for the 2-methoxy-4-cresol oxidation to vanillin, giving great yield (90%) and with good turnover number (210), as well as other p-cresols in good to great yields. The catalytic performance was investigated and related to the structural, chemical and magnetic properties which determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). The effects of base to substrate molar ratio, catalyst concentration, temperature, and solvent on the conversion and selectivity patterns also have been studied. The investigation revealed that remarkable catalytic properties of CoOx@CN could be ascribed to the active species cobalt oxide, doped nitrogen and porous carbon with large surface area. The size of the catalyst is a key factor for catalyst performance. The ferromagnetic property of catalyst enables to recycle easily by an external magnetic field and reuse six successive times without significant activity loss.
- Liang, Cheng,Li, Xuefeng,Su, Diefeng,Ma, Qiyi,Mao, Jianyong,Chen, Zhirong,Wang, Yong,Yao, Jia,Li, Haoran
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p. 121 - 131
(2018/05/22)
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- Graphene Oxide Promoted Oxidative Bromination of Anilines and Phenols in Water
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The mildly acidic and oxidative nature of graphene oxide, with its large surface area available for catalytic activity, has been explored in aromatic nuclear bromination chemistry for the first time. The versatile catalytic activity of graphene oxide (GO) has been used to selectively and rapidly brominate anilines and phenols in water. The best results were obtained at ambient temperatures using molecular bromine in a protocol promoted by oxidative bromination catalyzed by GO; these transformations proceeded with 100% atom economy with respect to bromine and high selectivities for the tribromoanilines and -phenols. Reduced graphene oxide (r-GO) was observed to form after the second recycle (third use) of GO. This technique is also effective with N-bromosuccinimide (NBS) as the brominating reagent. In the case of NBS, reactions were instantaneous and the GO displayed excellent recyclability without any loss of activity over several cycles.
- Ghorpade, Prashant Vasantrao,Pethsangave, Dattatray Appasha,Some, Surajit,Shankarling, Ganapati Subray
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p. 7388 - 7397
(2018/07/29)
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- A short and efficient total synthesis of the bromotyrosine-derived alkaloid psammaplysene A
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Psammaplysene A, an inhibitor of FOXO1a-mediated nuclear export, has been synthesized by a concise and improved route from tyrosine-derived acid and amine fragments which were easily constructed using commercially available p-hydroxybenzaldehyde and tyramine as starting material, respectively. The strategy provides an efficient access of psammaplysene analogues that can be explored for potential pharmaceutical or biological activities.
- Xu, Jingjing,Wang, Kai,Wu, Jinlong
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p. 13747 - 13749
(2018/04/25)
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- A trimethoprim intermediate 3, 5 - dibromo - 4 - hydroxybenzaldehyde preparation
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The invention provides a preparation method of trimethoprim midbody 3,5-dibromo-4-hydroxy benzaldehyde. The preparation method comprises the following steps of sequentially adding paracresol, ethanoic acid and zinc chloride in a reaction container; uniformly stirring; slowly adding benzyl trimethyl ammonium tribromide after cooling to the temperature of 0 DEG C; reacting for 1-2 hours at the temperature of 10-15 DEG C; heating to the temperature of 90-95 DEG C and reacting for 1.5-3 hours; performing reduced pressure distillation on reaction liquid to recycle acetic acid; adding water in a substrate, stirring, heating and performing backflow hydrolysis for 2-4 hours; cooling to room temperature; and filtering, washing and drying to obtain the 3,5-dibromo-4-hydroxy benzaldehyde. Reaction conditions of the preparation method are gentle, a technology is simple, reaction speed is high, the purity of products is above 98%, yield is above 93%, and BTMABr3 serves as a bromination reagent and replaces bromine with high toxicity. The preparation method has the advantages of safety, zero toxicity and environmental protection.
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Paragraph 0020; 0021; 0022; 0023; 0024; 0025-0028
(2017/08/25)
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- Concise total synthesis of aplysinellamides A and B
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Concise and efficient total syntheses of bromotyrosine-derived metabolites aplysinellamides A and B, isolated from Australian marine sponge Aplysinella sp., have been accomplished in seven steps. A condensation between cinnamic acid and Boc-D-lysine methyl ester was applied to form the amide skeleton as a key step.
- Gan, Haifeng,Huang, Yu,Feng, Weiyang,Zhu, Wentong,Guo, Kai
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p. 336 - 339
(2015/08/11)
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- Synthesis and Solvatochromism of Substituted 4-(Nitrostyryl)phenolate Dyes
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4-(Nitrostyryl)phenols 2a-9a were synthesized, and by deprotonation in solution, the solvatochromic phenolates 2b-9b were formed. Their absorption bands in the vis region of the spectra are due to π- π? electronic transitions, of an intramolecular charge-transfer nature, from the electron-donor phenolate toward the electron-acceptor nitroarene moiety. The frontier molecular orbitals and natural bond orbitals were analyzed for the protonated and deprotonated forms. The calculated geometries are in agreement with X-ray structures observed for 4a, 6a, and 8a. The HOMO-LUMO energy gaps suggest that, after their deprotonation, an increase in the electron delocalization is observed. In the protonated compounds, the HOMO is primarily localized over the phenol ring and the C=C bridge. After deprotonation, it extends toward the entire molecule, including the NO2 groups. The solvatochromism of each dye was studied in 28 organic solvents, and it was found that all compounds exhibit a reversal in solvatochromism, which is interpreted in terms of the ability of the media to stabilize their electronic ground and excited states to different extents. The Catalán multiparameter equation is used in the interpretation of the solvatochromic data, revealing that the most important contribution to the solute/solvent interaction is the hydrogen-bond donor acidity of the solvent.
- Stock, Rafaela I.,Nandi, Leandro G.,Nicoleti, Celso R.,Schramm, Adriana D. S.,Meller, Sheila L.,Heying, Renata S.,Coimbra, Daniel F.,Andriani, Karla F.,Caramori, Giovanni F.,Bortoluzzi, Adailton J.,Machado, Vanderlei G.
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p. 7971 - 7983
(2015/09/01)
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- Synthesis and antibacterial activities of cadiolides A, B and C and analogues
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The one-pot multicomponent synthesis of natural butenolides named cadiolides A, B, C and analogues has been realized. The antibacterial structure activity relationship shows that the presence of phenolic hydroxyl groups and the number and position of bromine atoms on the different aromatic rings are important features for antibacterial activity, besides it was demonstrated the tolerance of both benzene and furan ring at position 3 of the butenolide nucleus. Furthermore, none of the most relevant antibacterial compounds showed any cytotoxicity in freshly isolated human neutrophils.
- Boulangé, Agathe,Parraga, Javier,Galán, Abraham,Cabedo, Nuria,Leleu, Stéphane,Sanz, Maria Jesus,Cortes, Diego,Franck, Xavier
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p. 3618 - 3628
(2015/07/27)
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- A highly efficient approach to vanillin starting from 4-cresol
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A highly efficient approach to the famous flavor and fragrance compound vanillin has been developed starting from 4-cresol with the attention focused on improving the sustainability of all the reactions. The approach involves a three-step sequence of the quasi-quantitative selective clean oxybromination of 4-cresol, the high-yield selective aerobic oxidation of 2-bromo-4-cresol, and the quantitative methoxylation of 3-bromo-4-hydroxybenzaldehyde with the recovery of pure methanol. Herein, the pivotal oxidation and methoxylation reactions are logically investigated and developed into two concise methodologies. As a green alternative, the approach holds significant value for the sustainable manufacturing of vanillin. the Partner Organisations 2014.
- Jiang, Jian-An,Chen, Cheng,Guo, Ying,Liao, Dao-Hua,Pan, Xian-Dao,Ji, Ya-Fei
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p. 2807 - 2814
(2014/05/06)
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- Efficient Co(OAc)2-catalyzed aerobic oxidation of EWG-substituted 4-cresols to access 4-hydroxybenzaldehydes
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We reported an efficient ligand-free Co(OAc)2·4H 2O/NaOH/O2/ethylene glycol reaction system that enables selective aerobic oxidation of a wide range of substrates covering 2,6-di-EWG-, 2,3,6-tri-EWG-, 2-EWG-, and 2-EWG-6-EDG-substituted 4-cresols into the corresponding 4-hydroxybenzaldehydes. Based on the experimental investigations and well-defined p-benzoquinone methides, a plausible reaction mechanism was proposed. Considering the simplicity of the procedure and importance of the products, the methodology was expected to become a favorable and practical tool in related benzylic C(sp3)-H functionalization chemistry.
- Jiang, Jian-An,Du, Jia-Lei,Liao, Dao-Hua,Wang, Zhan-Guo,Ji, Ya-Fei
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supporting information
p. 1406 - 1411
(2014/03/21)
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- Practical Cu(OAc)2/TEMPO-catalyzed selective aerobic alcohol oxidation under ambient conditions in aqueous acetonitrile
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We reported a ligand-and additive-free Cu(OAc)2/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary and secondary benzylic alcohols, primary and secondary 1-heteroaryl alcohols, cinnamyl alcohols, and aliphatic alcohols to the corresponding aldehydes and ketones. This ambient temperature oxidation protocol is of practical features like aqueous acetonitrile as solvent, ambient air as the terminal oxidant, and low catalyst loading, presenting a potential value in terms of both economical and environmental considerations. Based on the experimental observations, a plausible reaction mechanism was proposed.
- Jiang, Jian-An,Du, Jia-Lei,Wang, Zhan-Guo,Zhang, Zhong-Nan,Xu, Xi,Zheng, Gan-Lin,Ji, Ya-Fei
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supporting information
p. 1677 - 1681
(2014/03/21)
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- Cu(OAc)2-catalyzed remote benzylic C(sp3)-H oxyfunctionalization for C=O formation directed by the hindered para-hydroxyl group with ambient air as the terminal oxidant under ligand- and additive-free conditions
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A hindered para-hydroxyl group-directed remote benzylic C(sp3)-H oxyfunctionalization has been developed for the straightforward transformation of 2,6-disubstituted 4-cresols, 4-alkylphenols, 4-hydroxybenzyl alcohols and 4-hydroxybenzyl alkyl ethers into various aromatic carbonyl compounds. The ligand- and additive-free Cu(OAc)2-catalyzed atmospheric oxidation mediated by ethylene glycol unlocks a facile, atom-economical, and environmentally benign C=O formation for the functionalization of primary and secondary benzyl groups. Due to the pharmaceutical importance of 4-hydroxybenzaldehydes and 4-hydroxyphenones, the methodology is expected to be of significant value for both fundamental research and practical applications.
- Jiang, Jian-An,Chen, Cheng,Huang, Jian-Gang,Liu, Hong-Wei,Cao, Song,Ji, Ya-Fei
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supporting information
p. 1248 - 1254
(2014/03/21)
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- N1,N1-dimethyl-N3-(3-(trifluoromethyl) phenethyl)propane-1,3-diamine, a new lead for the treatment of human African trypanosomiasis
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The natural product, convolutamine I (1), has anti-trypanosomal activity however it has a high molecular weight of 473 due to a presence of 3 bromine atoms. The synthesis of the natural product convolutamine I (1) together with its analogues are presented. A SAR study against Trypanosoma brucei brucei led to compounds with improved physico-chemical properties: lower molecular weight and lower log P while maintaining potency (with a slight 2-fold improvement).
- Pham, Ngoc B.,Deydier, Sophie,Labaied, Mehdi,Monnerat, Severine,Stuart, Kenneth,Quinn, Ronald J.
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p. 541 - 551
(2014/03/21)
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- Fluorescent analogs of the marine natural product psammaplin A: Synthesis and biological activity
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The symmetrical disulfide psammaplin A from the marine sponge Pseudoceratina sp. was synthesized and structurally altered by replacement of one of the α-(hydroxyimino)acyl units by a fluorescent 4-coumarinacetyl moiety. Thus, the first fluorescent analogs of psammaplin A were obtained. Structural variation also covered the substitution pattern of the phenyl ring. Cytotoxicity of psammaplin A against the mouse fibroblast cell line L-929 (IC50 0.42 μg mL-1) was about two-fold higher than that of the fluorescent hybrid compounds, whereas the disulfide containing two 4-coumarinacetyl moieties was inactive. Fluorescence microscopy revealed uptake of the 4-coumarinacetyl-α-(hydroxyimino)acyl hybrids into the cytoplasm leading to fluorescence in close proximity of the nuclear envelope, most likely in the Golgi apparatus. We did not observe strong fluorescence inside the nucleus, where most of the target histone deacetylases are located. We conclude that reduction of the disulfide probably takes place outside the nucleus. The psammaplin-derived thiol exhibited potent activity against histone deacetylase in the low nanomolar range, but diminished cytotoxicity. Antimicrobial activity of the new derivatives was also determined.
- Hentschel, Fabia,Sasse, Florenz,Lindel, Thomas
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experimental part
p. 7120 - 7133
(2012/09/22)
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- Synthesis, biochemical evaluation and rationalisation of a series of 3,5- dibromo derivatives of 4-hydroxyphenyl ketone-based compounds as probes of the active site of type 3 of 17β-hydroxysteroid dehydrogenase (17β-hsd3) and the role of hydrogen bonding interaction in the inhibition of 17β-HSD3
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We report the synthesis, evaluation and rationalisation of the inhibitory activity of a series of 3,5-dibromo derivatives of 4-hydroxyphenyl ketone as probes of the active site of the type 3 of 17β-hydroxysteroid dehydrogenase (17β-HSD3). The results support the important role of hydrogen bonding interaction in the inhibition of 17β-HSD3.
- Olusanjo, Moniola S.,Mashru, Shreena N.,Cartledge, Timothy,Ahmed, Sabbir
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scheme or table
p. 604 - 610
(2012/08/28)
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- An instant and facile bromination of industrially-important aromatic compounds in water using recyclable CaBr2-Br2 system
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Various industrially-important brominated intermediates have been instantly synthesized using aq. CaBr2-Br2 system as an efficient and recyclable brominating reagent under aqueous conditions at room temperature without the need for metal catalysts or acidic additives. Structurally-diverse phenol and aniline derivatives with strong electron-withdrawing groups such as carboxylic, nitro and formyl show remarkable reactivity to the brominating reagent and brominated in 92-98% yield with high purity (>99%) in a very short reaction time. Organic solvent-free conditions, a feature of the green chemistry, were successively used not only for the reactions but also for the isolation of products at the end of the reaction. The recycling of HBr by its neutralization, thereby generating additional amounts of industrially-important CaBr2 has been designed and developed. The brominating reagent has been recycled and regenerated, and the process was repeated up to 4 cycles after the fresh batch using the regenerated brominating reagent having almost identical selectivity and isolated yields, which seems to be the most promising methodology from the viewpoint of the green approach to organic synthesis.
- Kumar, Lalit,Mahajan, Tanu,Agarwal
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experimental part
p. 2187 - 2196
(2011/09/16)
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- Synthesis and evaluation of some novel dibenzo[b,d]furan carboxylic acids as potential anti-diabetic agents
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A series of novel dibenzo[b,d]furan mono-carboxylic acid derivatives were synthesized, characterized and evaluated for their ability to inhibit Protein Tyrosine Phosphatase 1B (PTP1B) in vitro in order to use them as potential anti-diabetic agents. Structure-activity relationship study led to the identification of potent compound 5E which inhibited PTP1B with IC50 value of 82 ± 0.43 nM. Compound 5E was screened in vivo as drug candidate for anti-diabetic activity using rosiglitazone maleate as the standard. Compound 5E showed significant reduction in body weight, fed-state whole blood glucose (WBG), fasting WBG, plasma glucose and plasma cholesterol levels and non-significant reduction in fasting plasma triglyceride levels in ob/ob mice. A series of dibenzo[b,d]furan carboxylic acids were synthesized and evaluated for anti-diabetic activity. Compound 5E inhibited PTP1B with IC50 of 82 nM and reduced WBG and plasma glucose in ob/ob mice.
- Lakshminarayana,Prasad, Y. Rajendra,Gharat, Laxmikant,Thomas, Abraham,Narayanan, Shridhar,Raghuram,Srinivasan,Gopalan, Balasubramanian
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experimental part
p. 3709 - 3718
(2010/11/04)
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- Discovering potent inhibitors against the β-hydroxyacyl-acyl carrier protein dehydratase (FabZ) of helicobacter pylori: Structure-based design, synthesis, bioassay, and crystal structure determination
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The discovery of HpFabZ inhibitors is now of special interest in the treatment of various gastric diseases. In this work, three series of derivatives (compounds 3, 4, and 5) were designed, synthesized, and their biological activities were investigated as potential HpFabZ inhibitors in a two phased manner. First, we designed and synthesized two series of derivatives (3a-r and 4a-u) and evaluated the enzyme-based assay against HpFabZ. Five compounds (3i-k, 3m, and 3q) showed potential inhibitory activity, with IC50 values less than 2 μM. Second, a focused combinatorial library containing 280 molecules was designed employing the LD1.0 program. Twelve compounds (5a-l) were selected and synthesized. The activity of the most potent compound 5h (IC 50) 0.86 μM) was 46 times higher than that of the hit 1. The high hit rate and the potency of the new HpFabZ inhibitors demonstrated the efficiency of the strategy for the focused library design and virtual screening.
- He, Lingyan,Zhang, Liang,Liu, Xiaofeng,Li, Xianghua,Zheng, Mingyue,Li, HongLin,Yu, Kunqian,Chen, Kaixian,Shen, Xu,Jiang, Hualiang,Liu, Hong
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experimental part
p. 2465 - 2481
(2010/03/03)
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- Comparison of structure in solid state of new 1,5-bis(4-cyano-2,6-dimethoxyphenoxy)alkanes by means of 13C CP/MAS NMR and X-ray diffraction
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The synthesis and structural studies in solid state of new 1,5-bis(4-cyano-2,6-dimethoxyphenoxy)-3-oxapentane 1 and 1,5-bis(4-cyano-2,6-methoxyphenoxy)pentane 2 are presented. The observed complicated network of intermolecular interaction with participation of nitrile groups could play a role in their interaction with the biological target. In vitro screen against 60 human tumor cell lines revealed that compound 1 has promising growth inhibitory power GI50 against SR (leukemia) and HOP-92 (non-small lung cancer) equal to 4.33×10-6 and 1.03×10-5 M, respectively.
- Zabiński, Jerzy,Wolska, Irena,Maciejewska, Dorota
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- Synthesis and biological evaluation of purealin and analogues as cytoplasmic dynein heavy chain inhibitors
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Cytoplasmic dynein plays important roles in membrane transport, mitosis, and other cellular processes. A few small-molecule inhibitors of cytoplasmic dynein have been identified. We report here the first synthesis of purealin, a natural product isolated from the sea sponge Psammaplysilla purea, which is known to inhibit axonemal dynein. Also described are the first syntheses, by modular amide coupling reactions, of the natural product purealidin A (a component of purealin) and a small library of analogues. The library was examined for inhibition of cytoplasmic dynein heavy chain and cell growth. The compounds showed effective antiproliferative activity against a mouse leukemia cell line but selective activities against human carcinoma cell lines. Purealin and some of the analogues inhibited the microtubule-stimulated ATPase activity of recombinant cytoplasmic dynein heavy chain motor domain. The inhibitory effect of purealin was concentration dependent and uncompetitive, supporting the hypothesis that it does not compete with the binding of ATP.
- Zhu, Guangyu,Yang, Fanglong,Balachandran, Raghavan,H??k, Peter,Vallee, Richard B.,Curran, Dennis P.,Day, Billy W.
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p. 2063 - 2076
(2007/10/03)
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- Regioselective and high-yielding bromination of aromatic compounds using hexamethylenetetramine-bromine
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A regioselective and highly efficient method for bromination of aromatic compounds in the presence of a stoichiometric amount of hexamethylenetetramine- bromine (HMTAB) as an efficient reagent in dichloromethane is reported. The selectivity depends on the temperature and nature of the substituent on the substrate. The reactivity of this reagent was increased by supporting it to silica gel for bromination of less activated compounds.
- Heravi, Majid M.,Abdolhosseini, Nafiseh,Oskooie, Hossein A.
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p. 8959 - 8963
(2007/10/03)
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- An expeditious convergent synthesis of a dibromotyrosine alkaloid inhibitor of mycothiol-S-conjugate amidase
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A quick, economic synthesis of the alkaloid 1, an inhibitor of mycothiol-S-conjugate amidase (MCA) is reported. Starting from low-cost, commercially available 4-hydroxybenzaldehyde, the nine-step synthesis involved dibromination and coupling with N-acetylglycine to give a stable methyloxazole intermediate 5 which was hydrolyzed, oximated and coupled to agmatine to yield the oxime in ～30% overall yield. It was not necessary to protect the oxime in the synthetic sequence thereby circumventing a deprotection step.
- Chanda, Bhanu M.,Sulake, Rohidas S.
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p. 6461 - 6463
(2007/10/03)
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- Tyrosine phosphatase inhibitors
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A compound of the formula (I): wherein X1 and X2 are the same or different and each is a bond or a spacer having 1 to 20 atom(s) in the main chain; one of R1 and R2 is a cycle group having substituent(s) selected from 1) an optionally substituted carboxy-C1-6 alkoxy group and 2) an optionally substituted carboxy-C1-6 aliphatic hydrocarbon group, wherein the cycle group optionally has additional substituent(s), and the other is an optionally substituted cycle group or a hydrogen atom; and R3, R4 and R5 are the same or different and each is a hydrogen atom or a substituent, or R4 may link together with R3 or R5 to form an optionally substituted ring; provided that when R3 is a hydrogen atom, R4 is a hydrogen atom and R5 is methyl, X2—R2 is not 4-cyclohexylphenyl; when R3 is 4-methoxyphenyl, R4 is a hydrogen atom and R5 is methyl, X2—R2 is not 4-methoxyphenyl; and when R1 or R2 is a hydrogen atom, the adjacent X1 or X2 is not a C1-7 alkylene; or a salt thereof exhibits a protein tyrosine phosphatase inhibitory action and is useful as a prophylactic or therapeutic agent for diabetes or the like.
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- Interesting product formation during O-alkylation and subsequent rearrangement of two building blocks of dibromotyrosine based natural products
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The O-alkylation (allylation/propargylation) of 3,5-dibromo-4-hydroxybenzaldehyde 1 and the corresponding acetophenone 2 results in the formation of aryl-aryl coupled product by loss of formyl groups, aryl-aryl ether and aryloxy acetone in addition to the expected O-allyl / propargyl ethers. While the thermal Claisen rearrangement of allyl ethers 1 and 2 furnishes the C-allyl products by loss of bromine, the propargyl ether 7 surprisingly resisted rearrangement and underwent oxidation to yield the corresponding carboxylic acid.
- Mallavadhani, Uppuluri V.,Mahapatra, Anita,Narasimhan,Sahoo
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p. 1460 - 1466
(2007/10/03)
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- Solid state nuclear bromination with N-bromosuccinimide. Part 2. Experimental and theoretical studies of reactions with some substituted benzaldehydes
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N-Bromosuccinimide reacts with aromatic aldehydes in the solid state to yield exclusively nuclear brominated products while a similar reaction in the solution phase produces a number of products under varied conditions. The reactivity and regioselectivity have been studied in terms of the energies of HOMO, HOMO-LUMO difference, reaction free energy, reaction conditions and crystal packing. Single crystal X-ray structural analysis of 3,4-dihydroxybenzaldehyde has been carried out. Crystal packing energies of some of the reactive and unreactive benzaldehydes indicate the importance of molecular bromine diffusion in the solid state.
- Sarma, Jagarlapudi A.R.P.,Nagaraju, Akula,Majumdar, Kanak K.,Samuel, Purnima M.,Das, Indira,Roy, Sujit,McGhie, Alistair J.
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p. 1119 - 1123
(2007/10/03)
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- Synthesis and structure of the marine ascidian 8-oxoadenine aplidiamine
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Alkylation of 8-oxoadenosine (13) with 4-benzyloxy-3,5-dibromobenzyl bromide (20), followed by Dimroth rearrangement and acid hydrolysis, provided N-(3,5-dibromo-4-hydroxybenzyl)-8-oxoadenosine (15). The 2'- deoxy version of this reaction sequence accomplished the first synthesis of N-(3,5-dibromo-4- hydroxybenzyl)-8-oxoadenine (16), which is the correct expression for marine ascidian purine aplidiamine.
- Itaya, Taisuke,Hozumi, Yoshitaka,Kanai, Tae,Ohta, Tomihisa
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p. 1297 - 1300
(2007/10/03)
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- Enzymatic oxidative coupling of hydroxyphenylglycine derivatives
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In contrast to N-protected tyrosine derivatives, N-protected hydroxy-D- phenylglycine derivatives underwent decarboxylation to give 4- hydroxybenzaldehyde under the normal incubation conditions. When both the carboxyl and amino groups of hydroxy-D-phenylglycine are blocked, the C-C and C-O coupling products were obtained in 48% and 32% yields respectively. No racemization of the chiral center was observed for all the substrates examined.
- Guo, Zhi-Wei,Machiya, Koji,Ma, You-An,Sih, Charles J.
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p. 5679 - 5682
(2007/10/03)
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- A novel two-step synthesis of 3,5-dibromo-4-hydroxybenzonitrile
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3,5-dibromo-4-hydroxybenzonitrile, bromoxynil (III) has been synthesized in two steps from p-cresol.
- Vidyasagar, A.,Nalawala, K. J.,Varshney, A. K.
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p. 872 - 873
(2007/10/02)
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- TWO NEW DIBROMOTYROSINE DERIVATIVES FROM THE CARIBBEAN SPONGE PSEUDOCERATINA CRASSA
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Two novel dibromotyrosine derivatives were isolated from the Caribbean sponge Pseudoceratina crassa (Hyatt).The structures of ethyl 3,5-dibromo-4-(3'-N,N-dimethylaminopropyloxy)cinnamate (1) and 3,5-dibromo-4-(3'-N,N-dimethylaminopropyloxy)cinnamic acid (2) were proposed on the basis of spectroscopic evidence and were confirmed by synthesis.
- Kassuehlke, Katharina E.,Faulkner, D. John
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p. 1809 - 1814
(2007/10/02)
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- Synthesis of 3,4,5-Trimethoxybenzaldehyde
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The copper(I)-catalyzed exchange of bromine by methoxide in 5-bromovanillin and in 3,5-dibromo-4-hydroxybenzaldehyde provides an efficient method for preparing 3,5-dimethoxy-4-hydroxybenzaldehyde, from which 3,4,5-trimethoxybenzaldehyde is obtained by methylation with dimethylsulfate.
- Manchand, Percy S.,Belica, Peter S.,Wong, Harry S.
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p. 2659 - 2666
(2007/10/02)
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- Synthesis of some hydroxymethylbromophenols of marine origin
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The hydroxymethylbromophenols 5, 7 and 9, isolated from marine source have been prepared in good yield.The bromo derivatives 1 and 2 of vanillin are demethylated to 4 and 6 which on borohydride reduction furnish 5 and 7 respectively.The dibromo-p-cresol (3) is oxidised to the aldehyde 8 which on borohydride reduction affords 9.
- Sudalai, A.,Rao, G. S. Krishna
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p. 858 - 859
(2007/10/02)
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- Solvolytic Elimination and Hydrolysis promoted by an Aromatic Hydroxy Group. Part 1. The Reaction of 2,6-Dibromo-4-dibromomethylphenol and of 2,6-Dibromo-4-bromomethylenecyclohexa-2,5-dienone with Water in 95percent 1,4-Dioxane
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The reaction of 2,6-dibromo-4-dibromomethylphenol with water to give the quinone methide, 2,6-dibromo-4-bromomethylenecyclohexa-2,5-dienone, together with 2,6-dibromo-4-hydroxybenzaldehyde has been studied in 95percent 1,4-dioxane.U.v. spectroscopy has been used to study the kinetic form of the reaction.At very low acidities, rapid conversion into the quinone methide occurs through the aryl oxide ion, and is followed by addition and replacement to give the aldehyde.At acidities greater than 1E-3M, reaction of the un-ionised phenol is dominant and follows a conventional SN1 pathway through a mesomeric carbocationic intermediate.Subsequent loss of a proton from this intermediate to give the quinone methide is competitive with its capture by the solvent (to give in several steps the related aldehyde) and by bromide ion (to give starting material).The mass-law constant for capture of the carbocation by bromide ion is very large (ca. 1E4 in this solvent), so that relatively small concentrations of hydrogen bromide convert the quinone methide back into the dibromomethylphenol by 1,6-addition.Solvent kinetic isotope effects on the individual reaction stages are reported.The rate of solvolysis of the phenol is much greater than would be predicted by the use of conventional linear free-energy parameters.
- Mare, Peter B. D. de la,Newman, Paul A.
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p. 231 - 238
(2007/10/02)
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- ENHANCEMENT OF THE CONJUGATIVE ELECTRON-RELEASING POWER OF THE HYDROXY-GROUP SHOWN BY THE KINETICS OF SOLVOLYSIS OF 2-BROMO-4-DIBROMOMETHYLPHENOL AND OF 2-BROMO-4-DIBROMOMETHYLANISOLE
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The relative rates and kinetic forms for the solvolyses of 2-bromo-4-dibromomethylphenol and its methyl ether lead to a new estimate (?+=-1.6) of the electron-releasing power of the hydroxy-group.
- Mare, Peter B. D. de la,Newman, Paul A.
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p. 1305 - 1308
(2007/10/02)
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- Process for aromatic ethers
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A process for the preparation of aromatic ethers by the bromination of a compound of the formula STR1 wherein R1, independently, is hydrogen, hydroxy, lower alkoxy, lower alkyl; m is an integer from 1-4, and A is --CHO, --COOR3 or lower alkyl, and subsequently treating the reaction product of the bromination step with an alkali metal alkoxide in the presence of cuprous halide or oxide, is described.
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