1706-11-2Relevant academic research and scientific papers
Pd-Catalyzed ipso, meta-Dimethylation of ortho-Substituted Iodoarenes via a Base-Controlled C-H Activation Cascade with Dimethyl Carbonate as the Methyl Source
Wu, Zhuo,Wei, Feng,Wan, Bin,Zhang, Yanghui
, p. 4524 - 4530 (2021/05/04)
A methyl group can have a profound impact on the pharmacological properties of organic molecules. Hence, developing methylation methods and methylating reagents is essential in medicinal chemistry. We report a palladium-catalyzed dimethylation reaction of ortho-substituted iodoarenes using dimethyl carbonate as a methyl source. In the presence of K2CO3 as a base, iodoarenes are dimethylated at the ipso- and meta-positions of the iodo group, which represents a novel strategy for meta-C-H methylation. With KOAc as the base, subsequent oxidative C(sp3)-H/C(sp3)-H coupling occurs; in this case, the overall transformation achieves triple C-H activation to form three new C-C bonds. These reactions allow expedient access to 2,6-dimethylated phenols, 2,3-dihydrobenzofurans, and indanes, which are ubiquitous structural motifs and essential synthetic intermediates of biologically and pharmacologically active compounds.
Active Molybdenum-Based Anode for Dehydrogenative Coupling Reactions
Beil, Sebastian B.,Müller, Timo,Sillart, Sydney B.,Franzmann, Peter,Bomm, Alexander,Holtkamp, Michael,Karst, Uwe,Schade, Wolfgang,Waldvogel, Siegfried R.
supporting information, p. 2450 - 2454 (2018/02/09)
A new and powerful active anode system that can be operated in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) has been discovered. In HFIP the molybdenum anode forms a compact, conductive, and electroactive layer of higher-valent molybdenum species. This system can replace powerful but stoichiometrically required MoV reagents for the dehydrogenative coupling of aryls. This electrolytic reaction is more sustainable and allows the conversion of a broad scope of activated arenes.
Sequential Birch reaction and asymmetric Ir-catalyzed hydrogenation as a route to chiral building blocks
Paptchikhine, Alexander,Itto, Kaori,Andersson, Pher G.
supporting information; experimental part, p. 3989 - 3991 (2011/06/09)
A range of 1,2,4-trisubstituted cyclohexadienes obtained from the Birch reaction were hydrogenated asymmetrically to produce synthetically valuable chiral compounds in high enantio- and diastereoselectivity. The Royal Society of Chemistry.
PROLYL HYDROXYLASE INHIBITORS
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Page/Page column 18-19, (2010/07/10)
The invention described herein relates to certain 2,4-dioxo-l,2,3,4-tetrahydro-7- quinazolinecarboxamide derivatives of formula (I) which are antagonists of HIF prolyl hydroxylases and are useful for treating diseases benefiting from the inhibition of this enzyme, anemia being one example.
Solid state S-methylation of thiols and O-methylation of phenols and naphthols with dimethyl sulfate under microwave irradiation
Heravi, Majid M.,Ahari, Neda Zamani,Oskooie, Hossein A.,Ghassemzadeh, Mitra
, p. 1701 - 1712 (2007/10/03)
Mild and efficient S-methylation of thiols and o-methylation of phenols and naphthals occurs with dimethyl sulfate (DMS) supported on basic alumina under microwave irradiation in solventless system. Copyright Taylor & Francis Inc.
The role of ion-molecule pair intermediates in acid-catalyzed solvolysis. General base-catalyzed formation of 4-methylbenzyl carbocation and its trapping by nucleophiles
Thibblin
, p. 7427 - 7433 (2007/10/02)
The specific acid-catalyzed hydrolysis of 3,6-dimethoxy-3,6-dimethyl-1,4- cyclohexadiene (1) in 25 vol % acetonitrile in water at 25 °C provides 2,4- dimethylphenol (2a), 2,5-dimethylphenol (2b), 2,4-dimethylanisole (3a), 4- methylbenzyl alcohol (4), and small amounts of 2,5-dimethylanisole (3b) and 4-methylbenzyl methyl ether (5). The formation of 3b and 5 is proposed to involve intramolecular rearrangement of carbocation-molecule pair intermediates. The formation of 4-methylbenzyl alcohol (4) is catalyzed by general bases, indicating that dehydronation of the cyclohexadienyl carbocation is rate-limiting in its reaction to benzylic products. The Bronsted parameter was measured with carboxylate anions as β = 0.28. The 4- methylbenzyl carbocation, which is postulated to be an intermediate in this reaction, discriminates between added nucleophiles and solvent water: k(SCN)/k(HOH) = 37, k(Cl)/K(HOH) = 9.8, k(EtOH)/k(HOH) = 1.9, and k(MeOH)/k(HOH) = 2.1 (ratios of second-order rate constants). The rate constant for reaction of the carbocation with solvent water is estimated as k(HOH) = 1.4 x 108 M-1s-1 (5.6 x 109 s-1), assuming a diffusion- controlled rate constant of 5 x 109 M-1s-1 for its reaction with thiocyanate anion. The nucleophilic selectivity values are considerably smaller than those exhibited by 4-methylbenzyl bromide under the same reaction conditions: k(Cl)/k(HOH) = 210, k(EtOH)/k(HOH) = 3.8, and k(MeOH)/k(HOH) = 5.3. These differences are concluded to be due to different mechanisms. The bromide reacts by a concerted bimolecular S(N)2 mechanism with chloride anion. With alcohols and water, the reactions occur either by a concerted uncoupled mechanism or via the ion pairs.
REACTIVITY OF 3,6-DIMETHOXY-3,6-DIMETHYLCYCLOHEXA-1,4-DIENE: NUCLEAR VERSUS BENZYLIC NUCLEOPHILIC SUBSTITUTION
Alonso, Francisco,Barba, Isidoro,Yus, Miguel
, p. 2069 - 2080 (2007/10/02)
The treatment of cis/trans-3,6-dimethoxy-3,6-dimethylcyclohexa-1,4-diene (ca. 1/1 mixture; easily prepared electrochemically in multigram scale from p-xylene) under acidic conditions (acetic, trifluoroacetic, sulfuric, or a Lewis acid) yields almost exclusively 2-methoxy-1,4-dimethylbenzene 4, through a trasposition reaction.The use of aqueous hydrochloric or hydrofluoric acid gives 2,5-dimethylphenol 12, and with hydrogen chloride a mixture of 2- and α-chloro-p-xylene (13, 14) is isolated.Different oxygen-, nitrogen-, and sulfur-containing nucleophiles (alcohols,thiols, or hydrazoic acid) react with 3 under acid catalysis giving the corresponding products resulting from a nuclear or/ and benzylic substitution on p-xylene (15 - 20).The reaction of compound 3 with organolithium reagents affords exclusively benzylic products 21 in a regiospecific manner.In all cases the mixtures of isomers are separated by column chromatography.The lithiation of compound 3 with lithium powder or lithium naphthalenide fails, giving p-xylene.A probable mechanism is proposed for the studied reactions.
Substituent and Ring Size Dependence of the 4J(Me-C-C-H) Coupling Constant
Collins, M. J.,Hatton, P. M.,Sternbell, S.,Tansey, C. W.
, p. 824 - 828 (2007/10/02)
The magnitude of the 4J proton-proton coupling constant across the fragment CH3-C-C-H (a probe of the bond order between the central sp2-sp2 hybridized carbon atoms) has been found to be essentially independent of substitution on a toluene fragment and the size of the ring containing the ortho-allylic fragment.The coupling constant is sensitive to direct substitution on the ortho-allilyc fragment, especially where the substituent is placed α to methyl group.KEY WORDS - 4J proton-proton coupling constant ortho-benzylic coupling constant ring size dependence substituent dependence
