共查询到20条相似文献,搜索用时 15 毫秒
1.
Alkylation of isopropylidene- and cyclohexylidenepropanedinitrile with phenacyl bromides gave 2,2-bis(2-aryl-2-oxoethyl)propanedinitriles. Direct alkylation of propanedinitrile with phenacyl bromides afforded only 2-(2-aryl-2-oxoethyl)propanedinitriles. 相似文献
2.
《Green Chemistry Letters and Reviews》2013,6(3):439-449
Abstract 3-Alkylindole derivatives were produced by ring opening of epoxides in the presence of magnesium oxide nanoparticles as an efficient catalyst. Solvent-free conditions, stoichiometric amounts of reactants, and improved reaction times and yields are the most important advantages of this method. MgO nanoparticles are synthesized successfully. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Brunauer- Emmet-Teller (BET) surface measurement were used to characterize the structure and morphology of the catalyst. 相似文献
3.
Regioselective, catalyst-controlled monoalkylations of cis-vicinal diol motifs in carbohydrate derivatives, using a diphenylborinic ester precatalyst, are described. Selective installation of benzyl, naphthylmethyl, 4-bromobenzyl and benzyloxymethyl protective groups at a single secondary hydroxy group of ten representative carbohydrate derivatives illustrates the scope of this method. This new mode of catalytic reactivity represents an operationally simple method to access useful monoalkylated building blocks while avoiding the use of stoichiometric quantities of organotin reagents. 相似文献
4.
Regioselective synthesis of macrocycles, incorporating 3‐oxo‐4‐amino‐1,2,4‐triazole derivatives, has been achieved by reactions involving N‐alkylation, utilizing appropriate 1, ω ‐dihaloalkanes in the presence of metal hydroxide. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:329–336, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20211 相似文献
5.
Reactions of heteroaromatic compounds with 3-methyl substituted 2-quinonyl boronic acids proceeded by 1,4-addition followed by spontaneous protodeboronation, leading directly to the Friedel-Crafts alkylation products instead of the commonly observed alkenylation derivatives resulting from quinones. The boronic acid acts as a temporary regiocontroller, making the system a highly reactive quinone equivalent and opening a direct access to 5,5-disubstituted cyclohexene-1,4-diones. 相似文献
6.
Exocyclic deprotonation and α alkylation with methyliodide of title compounds have been observed. A clarification of Hagemann ester ethylene ketal reactivity toward strong bases is given. 相似文献
7.
8.
A. V. Dezhenkov D. A. Cheshkov I. A. Prokhorov L. G. Dezhenkova V. I. Shvets Yu. G. Kirillova 《Russian Chemical Bulletin》2015,64(5):1100-1106
A method for the synthesis of 6-O-benzyl- and 6-O-benzyl-2-N-benzyloxycarbonyl-protected guanine derivatives starting from 2-amino-6-chloropurin is described. A regioselective alkylation of these N(9)-protected guanine derivatives gave the corresponding α-monomers of chiral peptide nucleic acids, the L-glutamic acid derivatives. It was shown that these compound do not inhibit (in the concentrations <20 µmol L–1) the topoisomerase I activity. 相似文献
9.
The acylated guanine-glyoxal adduct (I) has been alkylated with 4-bromobutyl acetate and in the presence of sodium hydride the reaction was regioselective to give 7-alkylguanine. 相似文献
10.
Steven Fletcher 《Tetrahedron letters》2010,51(22):2948-871
A novel synthetic route to N6-substitution of adenine is presented, employing the Mitsunobu reaction as the key step. A range of primary and secondary alcohols all coupled in very good to excellent yields within 30 min at 45 °C, offering a milder alternative to the traditional nucleophilic aromatic substitution of 6-chloropurine. The utility of this protocol is further demonstrated by its application to the syntheses of N6,N9-di-substituted adenines, including the potent and selective A1 adenosine receptor agonist N6-cyclopentyladenosine. 相似文献
11.
Min Chen Longqing Yang Yuzhen Li Yinhe Qu Guihua Pan Xiaoming Feng Xiaohua Liu 《中国科学:化学(英文版)》2024,(2):542-550
A highly efficient asymmetric allylic alkylation of cyclic and acyclic carbon nucleophiles with vinyl epoxides has been developed,which exhibits good functional group compatibility,high atomic and step economy.This protocol utilizes a strategy of synergistic catalysis with a chiral N,N’-dioxide/NiⅡ complex and an achiral Pd0 catalyst,generating a series of multisubstituted allylic alcohols with a quaternary carbon stereocenter in high yield and excellent regio-,Z/E-and enan... 相似文献
12.
Nevin Gürbüz Bekir Çetinkaya Jean-Luc Renaud Bernard Demerseman 《Tetrahedron letters》2006,47(4):535-538
Benzimidazolium halides are used for the first time as ligand precursors in ruthenium-catalyzed substitution of allylic carbonates and chlorides by carbon nucleophiles and phenols, respectively. After generation of diaminocarbene species upon deprotonation by tBuOK, their association with [Cp*Ru(MeCN)3]PF6 induces a very high regioselectivity in favor of the branched isomers when cinnamyl derivatives are used as starting substrates. They also provide good regioselectivities for the allylation of phenols by unsymmetrical aliphatic allylic substrates such as 3-chloro-4-phenylbut-1-ene, and thus provide a straightforward access to new allylic phenyl ethers. 相似文献
13.
Regioselective alkylation of 3,4-dihydro-2H-pyran by xanthate-mediated free radical nonchain process
An intermolecular xanthate-mediated free radical nonchain addition reaction is introduced for the regioselective alkylation of 3,4-dihydro-2H-pyran. Additionally, we observed that the free radical nonchain reaction depends on the nature of the radical precursor. 相似文献
14.
Regioselective alkylation of 2-alkyl-5,6,7,8-tetrahydro-3H-cycloheptimidazol-4-one (1) and 2-alkyl-3H-cycloheptimidazol-4-one (2) was investigated. 3-[2'-(1-tert-Butyl-1H-tetrazol-5-yl)biphenyl-4-ylmethyl]-2-propyl-5,6,7,8-tetrahydro-1H-cycloheptimidazol-4-one (6) was preferentially obtained under the conditions by using NaH in DMF or THF. On the other hand, 3-[2'-(1-tert-butyl-1H-tetrazol-5-yl)biphenyl-4-ylmethyl]-2-propyl-5,6,7,8-tetrahydro-3H-cycloheptimidazol-4-one (5), the synthetic intermediate compound of Pratosartan, was obtained selectively in the presence of n-Bu(4)NBr in toluene by using aqueous sodium hydroxide as a base. In this reaction, it was found that the concentration of the alkaline solution influences its regioselectivity. This selectivity was observed even for aldehyde and ester derivatives. 相似文献
15.
By treatment of β-carboline formamidine (1) with potassium hydride followed by an alkyl lithium reagent, both the pyrrole proton (N-9) and the proton at C-1 are removed. The resulting dianion (3) alkylates cleanly at C-1 and ultimately at N-9 or N-2. 相似文献
16.
A highly regioselective palladium-catalyzed alpha-alkylation of allylic bromides 1a,c-e and chloride 1b with substituted and unsubstituted benzylic Grignard reagents is reported. The resulting all-trans polyenehomobenzene derivatives were obtained in excellent yields and regioselectivity. These products were easily converted to abietane-type diterpenes (10-12) and tetracyclic polyprenoid compounds (13, 14) through a Lewis acid-promoted cascade polyene cyclization reaction. 相似文献
17.
Lee D Williamson CL Chan L Taylor MS 《Journal of the American Chemical Society》2012,134(19):8260-8267
Synthetic and mechanistic aspects of the diarylborinic acid-catalyzed regioselective monofunctionalization of 1,2- and 1,3-diols are presented. Diarylborinic acid catalysis is shown to be an efficient and general method for monotosylation of pyranoside derivatives bearing three secondary hydroxyl groups (7 examples, 88% average yield). In addition, the scope of the selective acylation, sulfonylation, and alkylation is extended to 1,2- and 1,3-diols not derived from carbohydrates (28 examples); the efficiency, generality, and operational simplicity of this method are competitive with those of state-of-the-art protocols including the broadly applied organotin-catalyzed or -mediated reactions. Mechanistic details of the organoboron-catalyzed processes are explored using competition experiments, kinetics, and catalyst structure-activity relationships. These experiments are consistent with a mechanism in which a tetracoordinate borinate complex reacts with the electrophilic species in the turnover-limiting step of the catalytic cycle. 相似文献
18.
Matsuo Y Iwashita A Abe Y Li CZ Matsuo K Hashiguchi M Nakamura E 《Journal of the American Chemical Society》2008,130(46):15429-15436
Monoaddition of Grignard reagents, in particular tri(organo)silylmethylmagnesium chlorides, to [60]fullerene took place smoothly in the presence of dimethylformamide to produce (organo)(hydro)[60]fullerenes, C60R(1)H, in good yield (up to 93% isolated yield). The hydrofullerene was then deprotonated to generate the corresponding anion, C60R(-), which was then alkylated to obtain 58pi-electron di(organo)[60]fullerenes, C60R(1)R(2), in good to high yield (up to 93% overall yield). The two-step methodology provides a wide variety of 1,4-di(organo)[60] fullerenes bearing the same or different organic addends on the [60] fullerene core. By changing the addends, one can control the chemical and physical properties of the compounds at the molecular and bulk levels. 相似文献
19.
The transition metal-catalyzed allylic alkylation represents a fundamentally important cross-coupling reaction for the construction of ternary carbon stereogenic centers. We have developed a regioselective and enantiospecific rhodium-catalyzed allylic alkylation of acyclic unsymmetrical allylic alcohol derivatives using copper(I) enolates to prepare beta-substituted ketones. This protocol represents a convenient asymmetric Claisen rearrangement surrogate in which alpha-substituted enolates permit the introduction of an additional stereogenic center. The synthetic utility of this transformation was highlighted in the construction of a trans-1,2-disubstituted cyclohexene and the total synthesis of (-)-sugiresinol dimethyl ether. Finally, we anticipate that copper(I) enolates may prove useful nucleophiles in related metal-catalyzed reactions. 相似文献
20.