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1.
Mervat M. Abdelkhalik Abdalla M. Negm Ayatt I. Elkhouly Mohammed H. Elnagdi 《Heteroatom Chemistry》2004,15(7):502-507
The reaction of 3‐amino‐5‐oxa‐2‐thia‐cyclopenta[a]naphthalene‐4‐one 2b with substituted acetylenes afforded C‐1 alkylation products. On the other hand, reaction of 17‐amino‐15‐methyl‐11‐oxa‐16‐thiacyclopenta[a]phenanthrene‐12‐one 5 with substituted acetylenes and electron‐poor olefins afforded the condensed thienopyridine derivatives 7 and 11a – c . The reaction of 5 with acrylonitrile and with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione afforded compounds 13 and 21 with loss of H2S via the expected [4 + 2] cycloaddition sequence. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:502–507, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20047 相似文献
2.
Xiaodong Si Yuanyuan Jia Xinqi Luan Luo Yang Yong Pei Wang Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2686-2690
A variety of benzofuranone‐based spiroisochromenes were originally designed and synthesized to gain insight into the oxa‐6π electrocyclic reaction of cis,cis‐1,8‐dioxatetraene for the first time. The stability of the 1,8‐dioxatetraene intermediate is governed by its steric congestion and can be fine‐tuned through modification of the backbone structure, leading to the reactivity differences in the 6π electrocyclic reaction and the emergence of photochromic properties. 相似文献
3.
Rainer Richter Uwe Schrder Lothar Beyer Jorge Angulo‐Cornejo Maria Lino‐Pacheco 《无机化学与普通化学杂志》2001,627(8):1877-1881
Mononuclear Copper(II) Complexes of Dioxaalkylene and Alkylene Bridged Bis‐isoureas By reaction of N‐benzoylthiocarbamic‐O,S‐diethylester with primary diamines (oxa)alkylene bridged isoureas 1 have been prepared. They yield with CuII neutral chelates 2 with tetradentate ligand coordination. The structures of the ligand 1 a and of the related CuII complex 2 a have been determined by X‐ray crystal structure analysis. They show an enamine tautomer in the ligand and a slightly tetrahedrally distorted coordination with an (oxa)alkylene bridge between the trans arranged N ligator atoms in the complex. 相似文献
4.
Organocatalytic Asymmetric 1,6‐Addition/1,4‐Addition Sequence to 2,4‐Dienals for the Synthesis of Chiral Chromans
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Pernille H. Poulsen Karla Santos Feu Bruno Matos Paz Prof. Dr. Frank Jensen Prof. Dr. Karl Anker Jørgensen 《Angewandte Chemie (International ed. in English)》2015,54(28):8203-8207
A novel asymmetric organocatalytic 1,6‐addition/1,4‐addition sequence to 2,4‐dienals is described. Based on a 1,6‐Friedel–Crafts/1,4‐oxa‐Michael cascade, the organocatalyst directs the reaction of hydroxyarenes with a vinylogous iminium‐ion intermediate to give only one out of four possible regioisomers, thus providing optically active chromans in high yields and 94–99 % ee. Furthermore, several transformations are presented, including the formation of an optically active macrocyclic lactam. Finally, the mechanism for the novel reaction is discussed based on computational studies. 相似文献
5.
Metal‐Free Reaction of ortho‐Carbonylated Alkynyl‐Substituted Arylaldehydes with Common Amines: Selective Access to Functionalized Isoindolinone and Indenamine Derivatives
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Dr. Ziping Cao Hongbo Zhu Dr. Xin Meng Jun Guan Qiang Zhang Laijin Tian Xuejun Sun Guang Chen Prof. Dr. Jinmao You 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16979-16985
Herein we describe a reaction of ortho‐carbonylated alkynyl‐substituted arylaldehydes with common primary amines that can provide functionalized isoindolinone and 3‐hydroxylindenamine products in high yields. Depending on the substituent size of primary amines, two distinct reaction pathways were exploited selectively, that are, an initial aza‐conjugate addition followed by hydrogen transfer to access isoindolinone framework and a unique oxa‐conjugate addition followed by Petasis–Ferrier rearrangement to afford indenamine derivatives. In the presence of Et3N, the reaction property of small primary amines was changed, proceeding to afford 3‐hydroxylindenamine derivatives efficiently. These products contain interesting substructures that exist in many natural products and bioactive molecules. The reaction features contain the use of transition‐metal‐free catalysts, simple operation, broad substrate scope, and product diversity. 相似文献
6.
Krishnendu B. Sahu Arindam Maity Shyamal Mondal Rupankar Paira Pritam Saha Subhendu Naskar Abhijit Hazra Sukdeb Banerjee Nirup B. Mondal 《Journal of heterocyclic chemistry》2013,50(Z1):E148-E155
A basic alumina‐supported microwave assisted simple methodology has been developed for the synthesis of aryl‐heteroaryl methanes (benzylated quinolones) via transition metal catalyzed cross‐coupling reaction of halo substituted polynuclear oxa‐aza quinolones with benzyl indium, an organometallic reagent easily derived from commercially available benzyl bromide. 相似文献
7.
Gold‐Catalyzed Cyclization of Furan‐Ynes bearing a Propargyl Carbonate Group: Intramolecular Diels–Alder Reaction with In Situ Generated Allenes
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Dr. Ning Sun Xin Xie Haoyi Chen Prof. Yuanhong Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14175-14180
Gold‐catalyzed cyclization of various furan‐ynes with a propargyl carbonate or ester moiety results in the formation of a series of polycyclic aromatic ring systems. The reactions can be rationalized through a tandem gold‐catalyzed 3,3‐rearrangement of the propargyl carboxylate moiety in furan‐yne substrates to form an allenic intermediate, which is followed by an intramolecular Diels–Alder reaction of furan and subsequent ring‐opening of the oxa‐bridged cycloadduct. It was found that the steric and electronic properties of phosphine ligands on the gold catalyst had a significant impact on the reaction outcome. In the case of 1,5‐furan‐yne, the cleavage of the oxa‐bridge in the cycloadduct with concomitant 1,2‐migration of the R1 group occurs to furnish anthracen‐1(2H)‐ones bearing a quaternary carbon center. For 1,4‐furan‐yne, a facile aromatization of the cycloadduct takes place to give 9‐oxygenated anthracene derivatives. 相似文献
8.
Organocatalytic Domino Oxa‐Michael/1,6‐Addition Reactions: Asymmetric Synthesis of Chromans Bearing Oxindole Scaffolds
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Kun Zhao Dr. Ying Zhi Tao Shu Dr. Arto Valkonen Prof. Dr. Kari Rissanen Prof. Dr. Dieter Enders 《Angewandte Chemie (International ed. in English)》2016,55(39):12104-12108
An asymmetric organocatalytic domino oxa‐Michael/1,6‐addition reaction of ortho‐hydroxyphenyl‐substituted para‐quinone methides and isatin‐derived enoates has been developed. In the presence of 5 mol % of a bifunctional thiourea organocatalyst, this scalable domino reaction affords 4‐phenyl‐substituted chromans bearing spiro‐connected oxindole scaffolds and three adjacent stereogenic centers in good to excellent yields (up to 98 %) and with very high stereoselectivities (up to >20:1 d.r., >99 % ee). 相似文献
9.
Judith C. Gallucci Yukiko Tamura Leo A. Paquette 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o656-o658
In the Diels–Alder reaction, the preferred addition of dienes syn to the O atom in cross‐conjugated cyclohexadienones containing an oxa‐spiro ring system is observed. The two structures reported here, namely rel‐(1R,4aR,9S,9aS,10R)‐4a,9,9a,10‐tetrahydro‐9,10‐diphenylspiro[9,10‐epoxyanthracene‐1(4H),2′‐oxiran]‐4‐one, C27H20O3, and rel‐(1R,4aS,9R,9aS,10S)‐4a,9,9a,10‐tetrahydro‐9,10‐diphenylspiro[9,10‐epoxyanthracene‐1(4H),2′‐oxetane]‐4‐one, C28H22O3, are the minor and sole products, respectively, of the reactions of diphenylisobenzofuran with two slightly different cyclohexadienones. These structures differ in the size of the oxa‐spiro ring, by one C atom, and in the relative configuration at the spirocyclic ring C atom, leading to some minor conformational differences between the two compounds. 相似文献
10.
Highly Convergent One‐Pot Four‐Component Regioselective Synthesis of Spiro‐pyranopyrazoles and Oxa‐aza‐[3.3.3]propellanes
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A concise and efficient route for the synthesis of spiro‐pyranopyrazoles and oxa‐aza‐[3.3.3]propellanes by simple regioselective multicomponent reaction of ninhydrin, malononitrile, hydrazine derivatives, and β‐keto esters or dimethyl acetylenedicarboxylate was developed. This protocol provides an alternative method for combinatorial and parallel syntheses in drug discovery. The value of this method lies in its simplicity, regioselectivity, and good yields. The structures of 3 and 4 were corroborated spectroscopically (IR, 1H‐ and 13C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Schemes 2 and 3). 相似文献
11.
Naifeng Hu Changming Dong Cuifang Zhang Guangxin Liang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6731-6734
The concise total syntheses of (?)‐indoxamycins A and B is reported. The chemistry features a seven‐step preparation of a highly congested [5.5.6] tricyclic advanced common intermediate from a readily available R‐carvone derivative. Key steps involve a Pauson–Khand reaction for the rapid construction of a basic scaffold bearing a quaternary carbon, a copper‐catalyzed Michael addition for the introduction of another adjacent all‐carbon quaternary stereocenter, and a tandem retro‐oxa‐Michael addition/1,2‐addition/oxa‐Michael addition for the installation of a trisubstituted olefin side chain. This synthetic strategy allows for easy access to both enantiomers of this family of natural products and their analogues from cost‐effective starting material through straightforward chemical transformations. 相似文献
12.
The development of efficient methods for stereocontrolled synthesis of polyol derivatives has been of continuing interest for the synthetic community. We describe herein tandem olefin cross‐metathesis/hemiacetalization/intramolecular oxa‐Michael addition of allylic/homoallylic alcohols, α,β‐unsaturated ketones, and aldehydes, which enabled the synthesis of syn‐1,2‐ and syn‐1,3‐diol derivatives in a step‐economical manner. A series of differentially protected polyol derivatives could be obtained in subsequent transformations via chemoselective/regioselective cleavage of the acetal moiety of the tandem reaction products. 相似文献
13.
Enhancement of Neighbouring‐Group Participation in Cu0‐Promoted Cross‐Coupling gem‐Difluoromethylenation of Aryl/Alkenyl Halides with 1,3‐Azolic Difluoromethyl Bromides
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Dr. Haizhen Jiang Wenjun Lu Kun Yang Dr. Guobin Ma Minjun Xu Dr. Jian Li Dr. Jianhua Yao Dr. Wen Wan Dr. Hongmei Deng Dr. Shaoxiong Wu Dr. Shizheng Zhu Dr. Jian Hao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):10084-10092
A copper(0)‐promoted direct reductive gem‐difluoromethylenation of unactivated aryl or alkenyl halides with benzo‐1,3‐azolic (oxa‐, thia‐ or aza‐) difluoromethyl bromides or 2‐bromodifluoromethyl‐1,3‐oxazoline has been developed for the construction of pharmaceutically important gem‐difluoromethylene‐linked twin molecules. The unique π‐conjugated aryl‐fused 1,3‐azolic moiety in difluoromethyl bromide substrates could stabilise the reaction intermediates, which promotes the reactivities, providing facile access to the cross‐coupling products in good to excellent yields, and allowing significant functional group tolerance. The reaction exhibits an enhanced neighbouring‐group‐participation effect. This method could provide a new strategy for the construction of gem‐difluoromethylene‐linked identical or nonidentical twin drugs through further functionalisation of 1,3‐azolic skeletons. 相似文献
14.
Delphine Josien‐Lefebvre Guillaume Desmares ClaudeLe Drian 《Helvetica chimica acta》2001,84(4):890-897
The total synthesis of the naturally occurring cyanoglucoside (−)‐bauhinin ( 1 ) was achieved starting from the optically pure oxatrinorbornenone 2 in 12 steps and 8% overall yield. The aglycone of (−)‐bauhinin was easily obtained from the optically pure oxatrinorbornenone derivative 6 by a Wittig‐Horner reaction followed by the opening of the oxa bridge. Glycosidation with tetra‐O‐isobutyryl‐D ‐glucosyl bromide 9 as the reagent in the Koenigs‐Knorr reaction afforded glucoside 10 in 58% yield, which, after photoisomerization and deprotection, gave (−)‐bauhinin ( 1 ). 相似文献
15.
Three new monoterpenoid indole alkaloids, vinmajorines C–E ( 1 – 3 ), along with 18 known analogues ( 4 – 21 ), were isolated from the whole plants of Vinca major. The new structures were elucidated as (5α,15β,16R,17α,19β,20α,21β)‐10,17‐dimethoxy‐21‐methyl‐18‐oxa‐5,16‐cycloyohimban‐19‐ol ( 1 ), (5α,15β,16R,17α,20α,21β)‐10‐methoxy‐21‐methyl‐18‐oxa‐5,16‐cycloyohimban‐17‐ol ( 2 ), and (5α,15β,16R,17α,20α,21β)‐10‐methoxy‐21‐methyl‐18‐oxa‐5,16‐cycloyohimban‐17‐yl acetate ( 3 ), respectively, by extensive NMR and MS analysis and comparison with known compounds. Compounds 1 – 3 were evaluated for their cytotoxic activities against five human cancer cell lines, compounds 1 and 3 showing moderate cytotoxic activities. 相似文献
16.
The stereoselective total synthesis of decytospolides A and B, two naturally occurring pyran derivatives, has been achieved using D ‐mannitol as the starting material. The intramolecular oxa‐Michael reaction has been employed to construct the tetrahydropyran ring of the molecules and Weinreb amide formation to generate their side chain with a keto function. 相似文献
17.
Diastereodivergent Catalysis Using Modularly Designed Organocatalysts: Synthesis of both cis‐ and trans‐Fused Pyrano[2,3‐b]pyrans
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Dr. Huicai Huang Swapna Konda Prof. Dr. John C.‐G. Zhao 《Angewandte Chemie (International ed. in English)》2016,55(6):2213-2216
Both enantiomers of cis‐ and trans‐fused 3,4,4a,8a‐tetrahydro‐2H,5H‐pyrano[2,3‐b]pyran‐7‐carboxylates have been obtained in high diastereoselectivities and enantioselectivities from the same starting materials using a tandem inverse‐electron‐demand hetero‐Diels–Alder/oxa‐Michael reaction catalyzed by modularly designed organocatalysts (MDOs). Diastereodivergence was achieved in these reactions through the direct control of the stereochemistry of the bridgehead atoms of the fused ring using new MDOs self‐assembled from both enantiomers of proline and cinchona alkaloid thiourea derivatives. 相似文献
18.
Karen Lienkamp Christoph F. Kins Sterling F. Alfred Ahmad E. Madkour Gregory N. Tew 《Journal of polymer science. Part A, Polymer chemistry》2009,47(5):1266-1273
Unprotected exo,exo‐5‐norbornene‐2,3‐dicarboxylic acid and exo,exo‐7‐oxa‐5‐norbornene‐2,3‐dicarboxylic acid were polymerized via ring‐opening metathesis polymerization. This reaction yielded polymers with molecular weights (Mn from GPC) ranging from 31 to 242 kg/mol and polydispersity indices between 1.05 and 1.12, using Grubbs' third generation catalyst. The water solubility as a function of pH value of the polymers was investigated by dynamic light scattering (DLS). DLS and acid‐base titration revealed that the oxanorbornene polymer was water soluble over a wider pH range than its norbornene analog. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1266–1273, 2009 相似文献
19.
Dr. Loïc Tomas Dr. Gustav Boije af Gennäs Dr. Marie Aude Hiebel Dr. Peter Hampson Dr. David Gueyrard Dr. Béatrice Pelotier Prof. Jari Yli‐Kauhaluoma Prof. Olivier Piva Prof. Janet M. Lord Prof. Peter G. Goekjian 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(24):7452-7466
The total synthesis of bistramide A and its 36(Z),39(S) and 36(Z),39(R) isomers shows that these compounds have different effects on cell division and apoptosis. The synthesis relies on a novel enol ether‐forming reaction for the spiroketal fragment, a kinetic oxa‐Michael cyclization reaction for the tetrahydropyran fragment, and an asymmetric crotonylation reaction for the amino acid fragment. Preliminary biological studies show a distinct pattern of influence of each of the three compounds on cell division, differentiation, and apoptosis in HL‐60 cells, thus suggesting that these effects are independent activities of the natural product. 相似文献
20.
Angle Chiaroni Claude Riche Sverinne Rigolet Jean‐Marie Mlot Joël Vebrel 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):473-474
The two title 5‐oxa‐2,6‐diazaspiro[3.4]octan‐1‐one adducts, 7‐benzoyl‐2‐(4‐methoxyphenyl)‐6‐phenyl‐5‐oxa‐2,6‐diazaspiro[3.4]octan‐1‐one, C25H22N2O4, (III), and 6‐tert‐butyl‐2‐(4‐methylphenyl)‐7‐phenyl‐5‐oxa‐2,6‐diazaspiro[3.4]octan‐1‐one, C22H26N2O2, (IV), were obtained from a stereospecific [3+2] 1,3‐cycloaddition of 3‐methylene azetidin‐2‐ones as dipolarophiles with nitrones. The lactam ring is conjugated with the p‐methoxyphenyl or p‐methylphenyl moiety. The envelope conformations of the isoxazolidine rings in (III) and (IV) are different, leading the substituents to be pseudo‐axial in (III) and pseudo‐equatorial in (IV). 相似文献