共查询到20条相似文献,搜索用时 31 毫秒
1.
Guan‐Sai Liu Yuan‐Shan Yao Peng Xu Shaozhong Wang Dr. Zhu‐Jun Yao Prof. Dr. 《化学:亚洲杂志》2010,5(6):1382-1388
An efficient total synthesis of (S)‐14‐azacamptothecin has been accomplished in 10 steps and 56 % overall yield from 5H‐pyrano[4,3‐d]pyrimidine 8 . A mild Hendrickson reagent‐triggered intramolecular cascade cyclization, a highly enantioselective dihydroxylation, and an efficient palladium‐catalyzed transformation of an O‐allyl into N‐allyl group are the key steps in the synthesis. This work provides a much higher overall yield than the previous achievement and shows sound flexibility for the further applications that will lead to new bioactive analogues. 相似文献
2.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1579-1582
Methods for positionally selective remote C−H functionalizations are in high demand. Herein, we disclose the first heterogeneous ruthenium catalyst for meta ‐selective C−H functionalizations, which enabled remote halogenations with excellent site selectivity and ample scope. The versatile heterogeneous Ru@SiO2 catalyst was broadly applicable and could be easily recovered and reused, which set the stage for the direct fluorescent labeling of purines. In contrast to palladium, rhodium, iridium, or cobalt complexes, solely the ruthenium catalysis manifold provided access to meta ‐halogenated purine derivatives, illustrating the unique power of ruthenium C−H activation catalysis. 相似文献
3.
With the reaction of bis(1,5‐cyclooctadiene)nickel(0) and trans‐penta‐2,4‐dienoic acid in the presence of tricyclohexylphosphine, a new more general method was developed to synthesize cyclic π3‐allyl‐carboxylato Ni(II) complexes, which are known to be intermediates in the C? C coupling of butadiene and CO2. The cyclic π3‐allyl‐carboxylato Ni(II) complex obtained is tested as a mediator in the electrochemical coupling reaction of butadiene and carbon dioxide. We also demonstrate the dependency on the coordination sphere by using platinum instead of nickel as the metal center. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
4.
《Journal of heterocyclic chemistry》2017,54(1):215-225
N,N,N',N'‐tetrabromobenzene‐1,3‐disulfonamide and poly(N ,N ’‐dibromo‐N‐ethyl‐benzene‐1,3‐disulfonamide) were used as efficient catalysts for one‐pot synthesis of new quinazoline derivatives from various aldehydes, 2‐amino‐benzophenone, and ammonium acetate in good to excellent yields and new benzopyrano[2,3‐d ]pyrimidine derivatives from salicylic aldehydes, various cyclic amines, and malononitrile in good to high yields. 相似文献
5.
Dr. Roman Savka M. Sc. Marvin Bergmann Yuki Kanai Sabine Foro Prof. Dr. Herbert Plenio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9667-9675
Based on 1‐amino‐4‐hydroxy‐triptycene, new saturated and unsaturated triptycene‐NHC (N‐heterocyclic carbene) ligands were synthesized from glyoxal‐derived diimines. The respective carbenes were converted into metal complexes [(NHC)MX] (M=Cu, Ag, Au; X=Cl, Br) and [(NHC)MCl(cod)] (M=Rh, Ir; cod=1,5‐cyclooctadiene) in good yields. The new azolium salts and metal complexes suffer from limited solubility in common organic solvents. Consequently, the introduction of solubilizing groups (such as 2‐ethylhexyl or 1‐hexyl by O‐alkylation) is essential to render the complexes soluble. The triptycene unit infers special steric properties onto the metal complexes that enable the steric shielding of selected areas close to the metal center. Next, chiral and meso‐triptycene based N‐heterocyclic carbene ligands were prepared. The key step in the synthesis of the chiral ligand is the Buchwald–Hartwig amination of 1‐bromo‐4‐butoxy‐triptycene with (1S,2S)‐1,2‐diphenyl‐1,2‐diaminoethane, followed by cyclization to the azolinium salt with HC(OEt)3. The analogous reaction with meso‐1,2‐diphenyl‐1,2‐diaminoethane provides the respective meso‐azolinium salt. Both the chiral and meso‐azolinium salts were converted into metal complexes including [(NHC)AuCl], [(NHC)RhCl(cod)], [(NHC)IrCl(cod)], and [(NHC)PdCl(allyl)]. An in situ prepared chiral copper complex was tested in the enantioselective borylation of α,β‐unsaturated esters and found to give an excellent enantiomeric ratio (er close to 90:10). 相似文献
6.
Ming Hu Jian‐Hong Fan Yu Liu Xuan‐Hui Ouyang Ren‐Jie Song Jin‐Heng Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(33):9713-9716
A new metal‐free oxidative radical [2+2+1] carbocyclization of benzene‐linked 1,n‐enynes with two C(sp3) H bonds adjacent to the same heteroatom is described. This method achieves two C(sp3) H oxidative functionalizations and an annulation, thus providing efficient and general access to a variety of fused five‐membered carbocyclic hydrocarbons. 相似文献
7.
Liejin Zhou Bing Xu Junliang Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(31):9220-9224
An unprecedented strategy for in situ generation of indole‐based ortho‐quinodimethanes (oQDMs) from 2‐methyl‐3‐alkylmethylindoles by either a metal‐free DDQ‐ or BQ‐mediated dehydrogenative process was developed. These oQDMs were trapped by electron‐deficient dienophiles to provide a facile approach to synthetically valuable tetrahydrocarbazoles, carbazoles, and hetereoacenes. The salient features of this transformation include direct C(sp3) H bond functionalizations, readily available starting materials, metal‐free conditions, high efficiency, operational simplicity, and ease of scale‐up. 相似文献
8.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(47):15327-15331
The para ‐selective C−H alkylation of aniline derivatives furnished with a pyrimidine auxiliary is herein reported. This reaction is proposed to take place via an N−H‐activated cyclometalate formed in situ. Experimental and DFT mechanistic studies elucidate a dual role of the ruthenium catalyst. Here the ruthenium catalyst can undergo cyclometalation by N−H metalation (as opposed to C−H metalation in meta ‐selective processes) and form a redox active ruthenium species, to enable site‐selective radical addition at the para position. 相似文献
9.
Metal‐Free Dehydrogenative Diels–Alder Reactions of 2‐Methyl‐3‐Alkylindoles with Dienophiles: Rapid Access to Tetrahydrocarbazoles,Carbazoles, and Heteroacenes 下载免费PDF全文
Liejin Zhou Bing Xu Prof. Dr. Junliang Zhang 《Angewandte Chemie (International ed. in English)》2015,54(31):9092-9096
An unprecedented strategy for in situ generation of indole‐based ortho‐quinodimethanes (oQDMs) from 2‐methyl‐3‐alkylmethylindoles by either a metal‐free DDQ‐ or BQ‐mediated dehydrogenative process was developed. These oQDMs were trapped by electron‐deficient dienophiles to provide a facile approach to synthetically valuable tetrahydrocarbazoles, carbazoles, and hetereoacenes. The salient features of this transformation include direct C(sp3)? H bond functionalizations, readily available starting materials, metal‐free conditions, high efficiency, operational simplicity, and ease of scale‐up. 相似文献
10.
One‐Pot Synthesis of (1,2,3‐Triazolyl)methyl 3,4‐Dihydro‐2‐oxo‐1H‐pyrimidine‐5‐carboxylates as Potentially Active Antimicrobial Agents 下载免费PDF全文
Minoo Dabiri Peyman Salehi Mahboubeh Bahramnejad Majid Koohshari Atousa Aliahmadi 《Helvetica chimica acta》2014,97(3):375-383
A simple and efficient one‐pot four‐component procedure has been developed for the synthesis of a wide range of compounds containing the (triazolyl)methyl oxo‐pyrimidine‐carboxylate system from propargyl β‐keto esters, various azides, aldehydes, and urea in the presence of catalytic amounts of (AcO)2Cu/sodium ascorbate in AcOH. The method worked well with different aryl and heteroaryl aldehydes, and for a variety of substituents in the triazolyl part of the molecule. The antimicrobial activities of the products were evaluated against two Gram‐positive and Gram‐negative bacteria, and one fungus. Compound 5j was active against Staphylococcus aureus and Candida albicans. 相似文献
11.
Christopher Cooze Raphael Dada Rylan J. Lundgren 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12374-12379
Methods for the addition of unsaturated nucleophiles to carbonyls to generate Z‐olefin products remain rare and often require either alkyl borane or zinc reductants, limiting their utility. Demonstrated here is that formic acid mediates the Rh‐catalyzed, Z‐selective coupling of dienes and aldehydes. The process is distinguished by broad tolerance towards reducible or electrophilic groups. Kinetic analysis suggests that generation of the catalytically active Rh intermediate by ligand dissociation is the rate‐determining step. The rapid generation and trapping of Rh‐allyl intermediates is key to preventing chain‐walking isomerization events that plague related protocols. Insights gained through this study may have wider implications in selective metal‐catalyzed hydrofunctionalization reactions. 相似文献
12.
A new and simple method for the synthesis of the primary allyl chlorides and bromides 9 – 16 from the secondary or tertiary allyl alcohols 3 – 8 and acyl halide was developed (Scheme 2, Table 1). Non‐commercially available secondary and tertiary allyl alcohols were synthesized from the related ketones and aldehydes via the addition of vinylmagnesium chloride. Mechanistic studies indicate that the alcohols were first acetylated by the acetyl halide and then protonated prior to substitution by the halide, Cl? or Br?, via an SN2′ reaction, to yield the primary halides (Scheme 5). 相似文献
13.
Eugene S. Gladkov Sergey M. Desenko Irina S. Konovalova Ulrich Groth Oleg V. Shishkin Elena V. Vashchenko Valentin A. Chebanov 《Journal of heterocyclic chemistry》2013,50(Z1):E189-E192
Three‐component heterocyclization of 4‐amino‐5‐carboxamido‐1,2,3‐triazole, thiopyran‐3‐one‐1,1‐dioxide, and aromatic aldehydes under ultrasonic and microwave irradiation was studied. Regardless of the reaction parameters, 5,6,7,9‐tetrahydro‐4H‐thiopyrano[3,2‐d][1,2,3]triazolo[1,5‐a]pyrimidine‐8,8‐dioxides were isolated as sole reaction products whose structures were proven with help of NMR data and X‐ray analysis. 相似文献
14.
Haisheng Wang Yan Zhang Wei Ye Stewart W. Schneller 《Journal of heterocyclic chemistry》2015,52(4):1132-1135
The synthesis of new members of the aristeromycin and neplaoncin A families of carbocyclic nucleosides possessing the 1H‐pyrazolo[3,4‐d]pyrimidine ring is reported. For this purpose, an adapted route to 4‐amino‐1H‐pyrazolo[3,4‐d]pyrimidine is described. 相似文献
15.
本文以等摩尔的芳醛,巴比妥酸(或1,3-二甲基巴比妥酸),5-氨基-2-甲基苯[d]噻唑为原料,以醋酸和乙二醇为溶剂,微波辐射下多组分一锅法合成了一系列新的吡啶[2,3-d]嘧啶衍生物。这种方法具有产率高,操作简便,反应时间短等优点。 相似文献
16.
Shahnaz Rostamizadeh Masoomeh Nojavan Reza Aryan Elyass Isapoor 《Helvetica chimica acta》2013,96(12):2267-2275
An efficient one‐pot procedure for the synthesis of 3‐amino‐6‐aryl‐2‐phenylpyrazolo[3,4‐d]pyrimidine derivatives, through the reaction of aldehydes, malononitrile, benzamidine hydrochloride, and hydrazine hydrate in the presence of basic alumina‐supported sodium acetate (AcONa/Al2O3) under reflux conditions, is reported. This protocol has some advantages, including the use of a simple and one‐pot synthetic approach to attain pyrazolo[3,4‐d]pyrimidine directly from four readily available starting materials, simple workup, high overall yields of the products, and the simultaneous conversion of a NO2 to an amino group, offering an opportunity to synthesize more complex structures. 相似文献
17.
Copper‐Catalyzed Enantioselective Allyl–Allyl Coupling between Allylic Boronates and Phosphates with a Phenol/N‐Heterocyclic Carbene Chiral Ligand 下载免费PDF全文
Yuto Yasuda Prof. Dr. Hirohisa Ohmiya Prof. Dr. Masaya Sawamura 《Angewandte Chemie (International ed. in English)》2016,55(36):10816-10820
Copper‐catalyzed enantioselective allyl–allyl coupling between allylboronates and either Z‐acyclic or cyclic allylic phosphates using a new chiral N‐heterocyclic carbene ligand, bearing a phenolic hydroxy, is reported. This reaction occurs with exceptional SN2′‐type regioselectivities and high enantioselectivities to deliver chiral 1,5‐diene derivatives with a tertiary stereogenic center at the allylic/homoallylic position. 相似文献
18.
Cristina Ferris M. Violante de Paz Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》2011,49(5):1147-1154
Three new polymerizable diols, based on mono‐, di‐, and tri‐O‐allyl‐L ‐arabinitol derivatives, were prepared from L ‐arabinitol as versatile materials for the preparation of tailor‐made polyurethanes with varied degrees of functionalization. Their allyl functional groups can take part in thiol‐ene reactions, to obtain greatly diverse materials. This “click” reaction with 2‐mercaptoethanol was firstly studied on the highly hindered sugar precursor 2,3,4‐tri‐O‐allyl‐1,5‐di‐O‐trityl‐L ‐arabinitol, to apply it later to macromolecules. A polyurethane with multiple pendant allyl groups was synthesized by polyaddition reaction of 2,3,4‐tri‐O‐allyl‐L ‐arabinitol with 1,6‐hexamethylene diisocyanate, and then functionalized by thiol‐ene reaction. The coupling reaction took place in every allyl group, as confirmed by standard techniques. The thermal stability of the novel polyurethanes was investigated by thermogravimetric analysis and differential scanning calorimetry (DSC). This strategy provides a simple and versatile platform for the design of new materials whose functionality can be easily modified. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
19.
Oligonucleotides incorporating 7‐deaza‐2′‐deoxyxanthosine ( 3 ) and 2′‐deoxyxanthosine ( 1 ) were prepared by solid‐phase synthesis using the phosphoramidites 6 – 9 and 16 which were protected with allyl, diphenylcarbamoyl, or 2‐(4‐nitrophenyl)ethyl groups. Among the various groups, only the 2‐(4‐nitrophenyl)ethyl group was applicable to 7‐deazaxanthine protection being removed with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) by β‐elimination, while the deprotection of the allyl residue with Pd0 catalyst or the diphenylcarbamoyl group with ammonia failed. Contrarily, the allyl group was found to be an excellent protecting group for 2′‐deoxyxanthosine ( 1 ). The base pairing of nucleoside 3 with the four canonical DNA constituents as well as with 3‐bromo‐1‐(2‐deoxy‐β‐D ‐erythro‐pentofuranosyl)‐1H‐pyrazolo[3,4‐d]pyrimidine‐4,6‐diamine ( 4 ) within the 12‐mer duplexes was studied, showing that 7‐deaza‐2′‐deoxyxanthosine ( 3 ) has the same universal base‐pairing properties as 2′‐deoxyxanthosine ( 1 ). Contrary to the latter, it is extremely stable at the N‐glycosylic bond, while compound 1 is easily hydrolyzed under slightly acidic conditions. Due to the pKa values 5.7 ( 1 ) and 6.7 ( 3 ), both compounds form monoanions under neutral conditions (95% for 1 ; 65% for 3 ). Although both compounds form monoanions at pH 7.0, pH‐dependent Tm measurements showed that the base‐pair stability of 7‐deaza‐2′‐deoxyxanthosine ( 3 ) with dT is pH‐independent. This indicates that the 2‐oxo group is not involved in base‐pair formation. 相似文献
20.
2‐Amino‐4‐(4‐substitutedphenyl)‐5‐oxo‐4H,5H‐pyrano[2,3‐d]pyrido[1,2‐a]pyrimidine‐3‐carbonitrile‐derivatives 2–12 were synthesized via multi‐component condensation reactions of different aromatic aldehydes, 3H‐pyrido[1,2‐a]pyrimidine‐2,4‐dione 1 , and malononitrile by using ZnO nanoparticles as green chemistry, environmentally friendly catalyst under solvent‐free conditions. The present work creates a variety of biologically active heterocyclic compounds in excellent yield and a short time. The structures of all synthesized compounds were elucidated with the elemental analyses, IR, 1H NMR, and mass spectral data. 相似文献