Liu, Gang et al. published their research in Dyes and Pigments in 2012 | CAS: 10243-15-9

3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. The different substitution patterns in these heterocycles offer new opportunities for drug discovery and other applications in materials science.Product Details of 10243-15-9

Synthesis and photochromic properties of novel pyridine-containing diarylethenes was written by Liu, Gang;Liu, Ming;Pu, Shouzhi;Fan, Congbin;Cui, Shiqiang. And the article was included in Dyes and Pigments in 2012.Product Details of 10243-15-9 This article mentions the following:

Three isomeric pyridine-containing diarylethenes were synthesized to study the effects of nitrogen atom position (ortho, para, meta) on their photochromic properties. Among these diarylethenes, the example with the nitrogen atom at the ortho-position of pyridine displayed the largest absorption maximum and molar absorption coefficients The cyclization quantum yields increased in order of para < meta < ortho, whereas their cycloreversion quantum yields decreased in order of para > meta > ortho. Compared to the diarylethene with terminal Ph ring, those with a terminal pyridine showed enhanced cyclization quantum yields and emission intensities. Moreover, these pyridine-containing diarylethenes exhibited multi-addressable switching behavior under the stimulation of both proton and light. Addition of trifluoroacetic acid to the solutions of the diarylethenes resulted in notable color change, and their N-protonated forms also possessed excellent photochromism. These results indicated that the nitrogen atom position played a pivotal role in the process of photoisomerization of the diarylethenes. In the experiment, the researchers used many compounds, for example, 3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9Product Details of 10243-15-9).

3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. The different substitution patterns in these heterocycles offer new opportunities for drug discovery and other applications in materials science.Product Details of 10243-15-9

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Martin-Santamaria, Sonsoles et al. published their research in Organic & Biomolecular Chemistry in 2008 | CAS: 90560-10-4

6-Methoxybenzo[b]thiophene (cas: 90560-10-4) belongs to benzothiophene derivatives. Benzothiophene is a fused ring compound of thiophene ring and benzene ring, which is an important class of heterocycles with advantageous structures. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.Safety of 6-Methoxybenzo[b]thiophene

New scaffolds for the design of selective estrogen receptor modulators was written by Martin-Santamaria, Sonsoles;Rodriguez, Jose-Juan;de Pascual-Teresa, Sonia;Gordon, Sandra;Bengtsson, Martin;Garrido-Laguna, Ignacio;Rubio-Viqueira, Belen;Lopez-Casas, Pedro P.;Hidalgo, Manuel;de Pascual-Teresa, Beatriz;Ramos, Ana. And the article was included in Organic & Biomolecular Chemistry in 2008.Safety of 6-Methoxybenzo[b]thiophene This article mentions the following:

In the present work we report the synthesis of four new ER ligands which can be used as scaffolds for the introduction of the basic side chains necessary for antiestrogenic activity. Affinities and agonist/antagonist characterization of the ligands for both ERα and ERβ have been determined in a competitive radioligand assay, and in an in vitro coactivator recruitment functional assay, resp. Mol. modeling techniques have been used in order to rationalize the exptl. results. Compound 2 is reported as a novel ERβ-agonist/ERα-antagonist. Two compounds show an interesting antitumor profile towards two pancreatic cancer cell lines and have been selected for in vivo assays. In the experiment, the researchers used many compounds, for example, 6-Methoxybenzo[b]thiophene (cas: 90560-10-4Safety of 6-Methoxybenzo[b]thiophene).

6-Methoxybenzo[b]thiophene (cas: 90560-10-4) belongs to benzothiophene derivatives. Benzothiophene is a fused ring compound of thiophene ring and benzene ring, which is an important class of heterocycles with advantageous structures. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.Safety of 6-Methoxybenzo[b]thiophene

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Kano, Shinzo et al. published their research in Journal of Organic Chemistry in 1982 | CAS: 10243-15-9

3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9) belongs to benzothiophene derivatives. Benzothiophene is used as starting material for the synthesis of bioactive molecules. The core structure is a part of various pharmaceutical substances and natural products. The different substitution patterns in these heterocycles offer new opportunities for drug discovery and other applications in materials science.Recommanded Product: 10243-15-9

Synthesis of 6-thiaellipticine and related compounds via heterocyclic o-quinodimethane intermediates was written by Kano, Shinzo;Mochizuki, Naoki;Hibino, Satoshi;Shibuya, Shiroshi. And the article was included in Journal of Organic Chemistry in 1982.Recommanded Product: 10243-15-9 This article mentions the following:

Pyrolysis of tertiary alcs. I (R = 2-pyridyl, R1 = Me,Et) at 400 °C for 7 min gave benzo[b]thieno[3,2-g]quinolines II (R2 = H, Me) and benzo[b]thieno[2,3-g]isoquinolines III (R2 = H, Me) through cyclization of the corresponding benzo[b]thiophene-2,3-quinodimethane intermediates. Pyrolysis of I (R = 3-pyridyl, R1 = Me,Et) afforded benzo[b]thieno[3,2-g]isoquinolines IV (R2 = H, Me). Pyrolysis of V gave 5-methyl-benzo[b]thieno[2,3-g]isoquinoline and III (R2 = H, Me). The alcs. VI (R3R4 = CH:CHCH:CH, X = O, S; R3 = R4 = H, X = S; R3R4 CH:NCH:CH, X = S) underwent similar cyclizations. In the experiment, the researchers used many compounds, for example, 3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9Recommanded Product: 10243-15-9).

3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9) belongs to benzothiophene derivatives. Benzothiophene is used as starting material for the synthesis of bioactive molecules. The core structure is a part of various pharmaceutical substances and natural products. The different substitution patterns in these heterocycles offer new opportunities for drug discovery and other applications in materials science.Recommanded Product: 10243-15-9

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Takeuchi, Kumiko et al. published their research in Bioorganic & Medicinal Chemistry Letters in 1999 | CAS: 90560-10-4

6-Methoxybenzo[b]thiophene (cas: 90560-10-4) belongs to benzothiophene derivatives. Benzothiophene scaffolds are of great importance due to its increased presence in bioactive molecules. It is found within the chemical structures of pharmaceutical drugs such as raloxifene, zileuton, sertaconazole, and also BTCP.Formula: C9H8OS

Dibasic benzo[b]thiophene derivatives as a novel class of active site directed thrombin inhibitors: 4. SAR studies on the conformationally restricted C3-side chain of hydroxybenzo[B]thiophenes was written by Takeuchi, Kumiko;Kohn, Todd J.;Sall, Daniel J.;Denney, Michael L.;McCowan, Jefferson R.;Smith, Gerry F.;Gifford-Moore, Donetta S.. And the article was included in Bioorganic & Medicinal Chemistry Letters in 1999.Formula: C9H8OS This article mentions the following:

A novel series of benzo[b]thiophene diamine thrombin inhibitors with a conformationally restricted C3-side chain was investigated. The constrained C3-side chain by a cyclohexyl ring contributed to not only an additive but also a synergistic effect on the thrombin inhibitory activity. The SAR studies resulted in the discovery of a potent thrombin inhibitor (I) that was over 750-fold more potent than the initial lead compound In the experiment, the researchers used many compounds, for example, 6-Methoxybenzo[b]thiophene (cas: 90560-10-4Formula: C9H8OS).

6-Methoxybenzo[b]thiophene (cas: 90560-10-4) belongs to benzothiophene derivatives. Benzothiophene scaffolds are of great importance due to its increased presence in bioactive molecules. It is found within the chemical structures of pharmaceutical drugs such as raloxifene, zileuton, sertaconazole, and also BTCP.Formula: C9H8OS

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Ren, Yi et al. published their research in Chemistry – An Asian Journal in 2010 | CAS: 6287-82-7

2,3-Dibromobenzo[b]thiophene (cas: 6287-82-7) belongs to benzothiophene derivatives. Benzothiophene finds use in research as a starting material for the synthesis of larger, usually bioactive structures. Due to its aromaticity, thiophenes do not exhibit the same properties as conventional thioethers.Application In Synthesis of 2,3-Dibromobenzo[b]thiophene

Ladder-type π-conjugated 4-hetero-1,4-dihydrophosphinines: A structure-property study was written by Ren, Yi;Baumgartner, Thomas. And the article was included in Chemistry – An Asian Journal in 2010.Application In Synthesis of 2,3-Dibromobenzo[b]thiophene This article mentions the following:

π-Conjugated six-membered 1,4-dihydrophosphinines containing a heteroatom (Si, P, S) at the 4 position were synthesized and systematically studied. X-ray crystallog. analyses showed that the central six-membered heterocyclic rings are almost planar. The sum of the angles around the phosphorus atom increases by 23° from the trivalent phosphorus to the phosphonium atom in the thiaphosphinine system, which is consistent with the NMR spectroscopic studies. UV/Vis spectroscopy and theor. calculations revealed that the communication between the phosphorus center and the benzothiophene moiety is enhanced by the incorporation of a sulfur atom into the mol. scaffold. The increased conjugation endows the thiaphosphinines with interesting emission properties. Theor. calculations supported the postulation that the orbital coupling between the π system and a σ* orbital could be enhanced in the thiaphosphinine system, especially through a phosphonium center. Cyclic voltammetry studies revealed that the thiaphosphinine oxide, thiaphosphonium, and cis-diphosphinine oxide exhibit quasi-reversible reduction processes, which demonstrate that simple changes in the bridge heteroatoms help to efficiently tune the redox properties of the ladder-type 4-hetero-1,4-dihydrophosphinines. In the experiment, the researchers used many compounds, for example, 2,3-Dibromobenzo[b]thiophene (cas: 6287-82-7Application In Synthesis of 2,3-Dibromobenzo[b]thiophene).

2,3-Dibromobenzo[b]thiophene (cas: 6287-82-7) belongs to benzothiophene derivatives. Benzothiophene finds use in research as a starting material for the synthesis of larger, usually bioactive structures. Due to its aromaticity, thiophenes do not exhibit the same properties as conventional thioethers.Application In Synthesis of 2,3-Dibromobenzo[b]thiophene

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Matsuki, Yasuo et al. published their research in Nippon Kagaku Zasshi in 1965 | CAS: 7312-11-0

Methyl 5-bromobenzo[b]thiophene-2-carboxylate (cas: 7312-11-0) belongs to benzothiophene derivatives. Benzothiophene is used as starting material for the synthesis of bioactive molecules. The core structure is a part of various pharmaceutical substances and natural products. It is found within the chemical structures of pharmaceutical drugs such as zileuton, raloxifene, and sertaconazole, and also BTCP.COA of Formula: C10H7BrO2S

5-Bromothianaphthene derivatives was written by Matsuki, Yasuo;Shoji, Fusaji. And the article was included in Nippon Kagaku Zasshi in 1965.COA of Formula: C10H7BrO2S This article mentions the following:

p-BrC6H4SH (10.3 g.) in 2 g. Na and 50 ml. EtOH was treated with 10 g. MeCHBrCH(OMe)2 to give 4 g. p-BrC6H4SCH2CH2CH(OMe)2 (I), b7 168-9°. Similarly, p-BrC6H4SCH2Ac (II), b10 164-5°, m. 64-5°, and pBrC6H4SCH2Bz (III), m. 82-3°, were prepared in 76 and 44% yields, resp. Heating 3 g. I with 20 ml. polyphosphoric acid and 17 g. P2O5 2 hrs. at 180° gave 0.9 g. 2-methyl-5-bromothianaphthene, m. 91-2°. Similarly, II and III gave 3-methyl-5-bromothianaphthene, b10 151-2°, m. 40-1°, and 2-phenyl-5-bromothianaphthene (IV), m. 186-7°, in 31 and 35.2% yields, resp. Desulfurization of IV with Raney Ni gave (PhCH2)2. 5-Bromothianaphthene (V) (10.5 g.) in Et2O was treated with BuLi from 0.4 g. Li, 6.7 g. BuBr, and 80 ml. Et2O and poured onto solid CO2 to give 8.5 g. 5-bromothianaphthene-2-carboxylic acid (VI), m. 234-5°; Me ester m. 97-8°. Treating 5 g. VI with SOCl2 in C6H6 gave chloride, m. 76-8°, 4.5 g. of which was treated with Me2Cd (from 5.2 g. MeI, 1 g. Mg, 50 ml. Et2O, and 1.9 g. CdCl2) to give 2.6 g. 2-acetyl-5-bromothianaphthene (VII), m. 112-13°; 2,4-dinitrophenylhydrazone m. 288-9°. Treating 0.5 g. VII with 0.5 g. H2SO4, 6 ml. AcOH, and 0.25 g. NaN3 at 85° and heating 8 hrs. at 95-8° gave 0.15 g. 2-acetamido-5-bromothianaphthene, m. 238-9°, which was hydrolyzed to 2-amino-5bromothianaphthene sulfate, m. 250-5° (decomposition). V (5.7 g.) was lithiated as above and treated with 4.5 g. Br to give 2.1 g. 2,5-dibromothianaphthene, m. 66.5-7.5°. 5-Bromo-2-thianaphthenyllithium (VIII) was treated with HCONMe2 to give 73% 2formyl-5-bromothianaphthene (IX), m. 119-20°. Heating IX, CH2(CO2H)2, C5H5N, and piperidine gave 68% 3-(5-bromo-2thianaphthenyl)acrylic acid, m. 262-3°, which was reduced with 5% Na-Hg in EtOH-dioxane-H2O containing Na2CO3 to give 61% 3-(5-bromo-2-thianaphthenyl)propionic acid, m. 122-4°. VIII from 3.2 g. V was treated with 3 g. CuCl2 to give 0.9 g. bis(5bromo-2-thianaphthenyl), m. 192-3°. V (3 g.) was treated with BuLi from 0.24 g. Li and 2.7 g. BuBr and carbonated to give thianaphthene-2,5-dicarboxylic acid, m. >310°; di-Me ester m. 152-3°. Adding 6.4 g. AlCl3 to 10 g. V and 3.7 g. AcCl in 50 g. PhNO2 gave 8 g. 3-acetyl-5-bromothianaphthene (X), m. 91-2°. Oxidation of × with NaOCl gave 5-bromothianaphthene-3-carboxylic acid, m. 285-6°; Me ester m. 78-9°. Schmidt reaction of × as above gave 70% 3-acetamido-5-bromothianaphthene, m. 226-7°, which was hydrolyzed to give 3-amino-5-bromothianaphthene sulfate, m. 235-40° (decomposition). V (5.7 g.) and 3.6 g. NaOAc in 20 ml. CHCl3 was treated with 5.6 g. Br in 10 ml. CHCl3 to give 6.1 g. 3,5-dibromothianaphthene (XI), m. 98-9°. Treating 1.4 g. XI with 2.7 g. MeI and 1.4 g. Mg in Et2O and treating the product with solid CO2 gave 77.3% thianaphthene-3,5-dicarboxylic acid, m. >310°. The results of substitution were compared with electron d. from mol. orbital calculations In the experiment, the researchers used many compounds, for example, Methyl 5-bromobenzo[b]thiophene-2-carboxylate (cas: 7312-11-0COA of Formula: C10H7BrO2S).

Methyl 5-bromobenzo[b]thiophene-2-carboxylate (cas: 7312-11-0) belongs to benzothiophene derivatives. Benzothiophene is used as starting material for the synthesis of bioactive molecules. The core structure is a part of various pharmaceutical substances and natural products. It is found within the chemical structures of pharmaceutical drugs such as zileuton, raloxifene, and sertaconazole, and also BTCP.COA of Formula: C10H7BrO2S

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Pradhan, Tarun Kanti et al. published their research in ARKIVOC (Gainesville, FL, United States) in 2003 | CAS: 90560-10-4

6-Methoxybenzo[b]thiophene (cas: 90560-10-4) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.SDS of cas: 90560-10-4

Certain applications of heteroatom directed ortho-metalation in sulfur heterocycles was written by Pradhan, Tarun Kanti;Ghosh, Sukhen Chandra;De, Asish. And the article was included in ARKIVOC (Gainesville, FL, United States) in 2003.SDS of cas: 90560-10-4 This article mentions the following:

Substituted benzothiophenes are prepared via heteroatom directed ortho-metalation of di-Et arylamides to introduce a methylsulfanyl group which upon deprotonation underwent intramol. cyclization to form intermediate thioindoxyls that are reduced with sodium borohydride to the corresponding benzothiophene derivative Addnl., heteroatom directed ortho-metalation of benzothiophenes is demonstrated to prepare benzothiophene analogs and heterocyclic analogs. This data is accompanied by a review of work from the author’s laboratory regarding application of directed ortho-metalation in sulfur heterocycles. In the experiment, the researchers used many compounds, for example, 6-Methoxybenzo[b]thiophene (cas: 90560-10-4SDS of cas: 90560-10-4).

6-Methoxybenzo[b]thiophene (cas: 90560-10-4) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.SDS of cas: 90560-10-4

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Li, Zhan-Xian et al. published their research in Journal of Physical Chemistry C in 2008 | CAS: 10243-15-9

3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. It is also used in the manufacturing of dyes such as thioindigo.Recommanded Product: 10243-15-9

Reconfigurable Cascade Circuit in a Photo- and Chemical-Switchable Fluorescent Diarylethene Derivative was written by Li, Zhan-Xian;Liao, Long-Yan;Sun, Wei;Xu, Chun-Hu;Zhang, Chao;Fang, Chen-Jie;Yan, Chun-Hua. And the article was included in Journal of Physical Chemistry C in 2008.Recommanded Product: 10243-15-9 This article mentions the following:

A new unsym. diarylethene derivative 1-{4-(5-methoxy-2-(2-pyridyl)thiazolyl)}-2-{3-(2-methylbenzo[b]thiophenyl)}hexafluorocyclopentene (1) was designed and synthesized. Fluorescence behaviors of 1 are multiswitched through protonation, coordination, and photochem. reactions due to the existence of multiple binding sites. Thus, the cooperation of chem. and optical input signals cascades several fundamental logic gates within the open form (1O) or closed form (1C) of 1, and the logic functions in 1O and 1C are reversible with photo-switch. Furthermore, photo-switch reversibly reconfigures logic functions from an INHIBIT logic gate (1C) to a half-subtractor (1O). In the experiment, the researchers used many compounds, for example, 3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9Recommanded Product: 10243-15-9).

3-Bromo-2-methylbenzo[b]thiophene (cas: 10243-15-9) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. It is also used in the manufacturing of dyes such as thioindigo.Recommanded Product: 10243-15-9

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Ushijima, Sousuke et al. published their research in Synlett in 2010 | CAS: 55219-11-9

Benzo[b]thiophene-2-carbonitrile (cas: 55219-11-9) belongs to benzothiophene derivatives. Benzothiophene scaffolds are of great importance due to its increased presence in bioactive molecules. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.Related Products of 55219-11-9

One-pot conversion of aromatic bromides and aromatics into aromatic nitriles was written by Ushijima, Sousuke;Togo, Hideo. And the article was included in Synlett in 2010.Related Products of 55219-11-9 This article mentions the following:

Various aromatic bromides and iodides were smoothly converted into the corresponding aromatic nitriles in good to moderate yields by sequential treatment with BuLi and DMF, followed by treatment with I2 in aqueous NH3. The same treatment of typical aromatics and heteroaromatics also provided the corresponding aromatic nitriles in good yields. The present reactions are novel 1-pot methods for the preparation of aromatic nitriles from aromatic bromides and aromatics, resp., through the formation of aryllithiums and their DMF adducts. In the experiment, the researchers used many compounds, for example, Benzo[b]thiophene-2-carbonitrile (cas: 55219-11-9Related Products of 55219-11-9).

Benzo[b]thiophene-2-carbonitrile (cas: 55219-11-9) belongs to benzothiophene derivatives. Benzothiophene scaffolds are of great importance due to its increased presence in bioactive molecules. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.Related Products of 55219-11-9

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem

 

Akay, Senol et al. published their research in Chemical Biology & Drug Design in 2007 | CAS: 6287-82-7

2,3-Dibromobenzo[b]thiophene (cas: 6287-82-7) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.Reference of 6287-82-7

Synthesis and evaluation of dual wavelength fluorescent benzo[b]thiophene boronic acid derivatives for sugar sensing was written by Akay, Senol;Yang, Wenqian;Wang, Junfeng;Lin, Li;Wang, Binghe. And the article was included in Chemical Biology & Drug Design in 2007.Reference of 6287-82-7 This article mentions the following:

Cell surface glycoproteins have been known to play very important roles in various physiol. and pathol. processes. Small mol. compounds capable of carbohydrate recognition can be very useful for the development of sensing, diagnostic, and therapeutic agents. Along this line, the authors are interested in developing water-soluble fluorescent boronic acid compounds for carbohydrate recognition. As such, a series of benzo[b]thiophene boronic acid derivatives have been synthesized and their fluorescent properties analyzed at physiol. pH. Benzo[b]thiophene derivatives were a new type of fluorescent reporter compounds capable of dual fluorescent emission under physiol. pH conditions. Many of the synthesized Compounds showed unusual emission wavelength shifts upon binding of sugars. These boronic acids will be useful tools for building glycoprotein biosensors for biol. applications. In the experiment, the researchers used many compounds, for example, 2,3-Dibromobenzo[b]thiophene (cas: 6287-82-7Reference of 6287-82-7).

2,3-Dibromobenzo[b]thiophene (cas: 6287-82-7) belongs to benzothiophene derivatives. Benzothiophene is relatively a stable molecule. The electrophilic substitution of benzothiophene systems is much less regioselective than that of indoles. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization.Reference of 6287-82-7

Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem