Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry最新文献_第7页

A radical version of the bromine cyclization of alkenols 烯醇的溴环化的原子团形式

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-07-01 DOI: 10.1016/S1387-1609(01)01286-5

Jens Hartung, Rainer Kneuer, Thomas Michael Kopf, Philipp Schmidt

{"title":"A radical version of the bromine cyclization of alkenols","authors":"Jens Hartung, Rainer Kneuer, Thomas Michael Kopf, Philipp Schmidt","doi":"10.1016/S1387-1609(01)01286-5","DOIUrl":"10.1016/S1387-1609(01)01286-5","url":null,"abstract":"<div>The scope of an alkoxyl radical version of the classical bromine cyclization was explored. Oxygen-centered radicals were generated in photochemically initiated radical chain reactions from N-alkenoxy-4-(p-chlorophenyl)thiazole-2(3H)-thiones 5a–c, N-alkenoxy-4-methylthiazole-2(3H)-thiones 13, 14, 21, rac-23, and N-alkenoxypyridine-2(1H)-thiones 6d–f, 16, rac-25. Thus, 2-(2-bromopropyl)-substituted tetrahydrofurans 4a–c, which are minor compounds (< 10 %) in NBS-mediated bromine cyclizations of corresponding alkenols 1a–c, were prepared in 87–90 % yield and with good to excellent diastereoselectivities. Further, photochemical conversions of O-alkyl thiohydroxamates 14, 16 and 21 in benzene and BrCCl3 afforded β-oxy-functionalized bromomethyl substituted tetrahydrofurans 29, 34, and 36. The results of this study indicate, that efficient 5-exo-trig cyclizations of β-oxy-substituted 4-penten-1-oxyl radical require an electronwithdrawing substituent at the β-heteroatom substituent. In the third part of the study a synthetically useful new access to oxabicyclo〚4.3.0〛nonanes rac-38 and rac-40 is reported which takes profit from highly diastereoselective 5-exo-trig-ring closures and, in case of the formation of rac-40, stereoselective bromine atom transfer.</div>","PeriodicalId":100305,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry","volume":"4 7","pages":"Pages 649-666"},"PeriodicalIF":0.0,"publicationDate":"2001-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1387-1609(01)01286-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80208237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Mechanisms of formation of free radicals in biological catalysis 自由基在生物催化中的形成机制

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-07-01 DOI: 10.1016/S1387-1609(01)01283-X

Marc Fontecave , Jean-Louis Pierre

引用次数: 6

Synthesis of peracetylated d-galactopyranosylidene dihalides 过乙酰化d-半乙酰氨基乙基二卤化物的合成

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-07-01 DOI: 10.1016/S1387-1609(01)01277-4

Jean-Pierre Praly, Jean-Charles Brendlé, Jan Klett, Fabien Péquery

{"title":"Synthesis of peracetylated d-galactopyranosylidene dihalides","authors":"Jean-Pierre Praly, Jean-Charles Brendlé, Jan Klett, Fabien Péquery","doi":"10.1016/S1387-1609(01)01277-4","DOIUrl":"10.1016/S1387-1609(01)01277-4","url":null,"abstract":"<div>Upon treatment with aluminium trichloride in absolute chloroform, β-d-galactopyranose penta-O-acetate was converted in high yield into tetra-O-acetyl-β-d-galactopyranosyl chloride. In the presence of N-bromosuccinimide in boiling carbon tetrachloride, homolytic substitution of the anomeric hydrogen atom in this β-chloride occurred selectively to afford tetra-O-acetyl-1-bromo-β-d-galactopyranosyl chloride, in admixture with minor amounts of tetra-O-acetyl-d-galactopyranosylidene chloride. Bromine substitution by fluorine took place with a low stereoselectivity in tetra-O-acetyl-1-bromo-β-d-galactopyranosyl chloride when treated with 1.25 equiv silver fluoride in acetonitrile, whereas tetra-O-acetyl-d-galactopyranosylidene fluoride could be prepared in 54 % yield with 3.3 equiv AgF. The gem-difluoride could be deacetylated quantitatively. Upon treatment with 1,4-diazabicyclo〚2.2.2〛octane, peracetylated 1-bromo-β-d-galactopyranosyl chloride underwent 1,2-elimination of hydrogen bromide to afford 2,3,4,6-tetra-O-acetyl-d-lyxo-hex-1-enopyranosyl chloride in 33 % yield.</div>","PeriodicalId":100305,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry","volume":"4 7","pages":"Pages 611-617"},"PeriodicalIF":0.0,"publicationDate":"2001-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1387-1609(01)01277-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85396549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Extension of the e.t. mechanism of aromatic nitration to the formation of Grignard reagents of RX (R = alkyl, aryl, cyclopropyl, vinyl). The ion pair collapse versus radical pair collapse hypothesis 芳香族硝化反应机理在RX (R =烷基、芳基、环丙基、乙烯基)格氏试剂生成中的延伸。离子对塌缩和自由基对塌缩假说

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-07-01 DOI: 10.1016/S1387-1609(01)01268-3

Ulf Berg , Nicolas Bodineau , Jean-Claude Négrel , Jean-Marc Mattalia , Vitaliy Timokhin , Kishan Handoo , Caroline Marchi , Michel Chanon

引用次数: 0

Complex examples of the Dowd–Beckwith rearrangement: a free radical route to 2-oxabicyclo 〚3.3.0〛octan-3,6-diones dow - beckwith重排的复杂例子:自由基途径生成2-氧沙比环〚3.3.0 <s:1>辛烷-3,6-二酮

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-07-01 DOI: 10.1016/S1387-1609(01)01274-9

David J Hart, Fabien Havas

引用次数: 1

Solvent effects in copper(I)-mediated 5-endo cyclisation of secondary bromo-enamides 铜(I)介导的仲溴酰胺5-内环化反应中的溶剂效应

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-07-01 DOI: 10.1016/S1387-1609(01)01275-0

Andrew J Clark , Colin P Dell , John P McDonagh

引用次数: 2

Recent results in the free radical mediated synthesis of enantiomerically pure, highly functionalized carbocycles from carbohydrates 自由基介导碳水化合物合成对映体纯、高功能化碳水化合物的最新研究结果

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-06-01 DOI: 10.1016/S1387-1609(01)01245-2

José Marco-Contelles, Mercedes Rodríguez-Fernández

{"title":"Recent results in the free radical mediated synthesis of enantiomerically pure, highly functionalized carbocycles from carbohydrates","authors":"José Marco-Contelles, Mercedes Rodríguez-Fernández","doi":"10.1016/S1387-1609(01)01245-2","DOIUrl":"10.1016/S1387-1609(01)01245-2","url":null,"abstract":"<div>The free radical cyclization strategy applied to precursors 1, 2 and 14 shows the power and the state of art of this ring closing method for the stereocontrolled synthesis of enantiomerically pure, highly functionalized carbocycles from carbohydrates. The tributyltin hydride mediated free radical cyclization of alkyne tethered N,N-diphenylhydrazones (1) and oxime ethers (2) give the stannylated aminocyclopentitol derivatives 4 and 11, respectively, in moderate yield and with complete stereoselectivity. The 6-exo-trig cyclization of aldehyde/oxime ether 14 derived from D-glucose has been revisited using tributyltin hydride as a reagent. This new protocol shows a superior stereoselection compared with the previous results obtained with samarium diiodide. In summary, an efficient protocol has been set up for the synthesis of enantiomerically pure, polyhydroxy aminocyclohexane derivatives, which are difficult to obtain by other methodologies.</div>","PeriodicalId":100305,"journal":{"name":"Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry","volume":"4 6","pages":"Pages 443-452"},"PeriodicalIF":0.0,"publicationDate":"2001-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1387-1609(01)01245-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77870657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Triethylborane-induced hydrogermylation of alkenes with tri-2-furylgermane 三乙基硼烷诱导烯烃与三-2-呋喃日耳曼的加氢化反应

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-06-01 DOI: 10.1016/S1387-1609(01)01248-8

Tomoaki Nakamura, Shinobu Tanaka, Hideki Yorimitsu, Hiroshi Shinokubo, Koichiro Oshima

引用次数: 1

Photochemical transformation of γ,δ-unsaturated ketone O-(p-cyanophenyl)oximes to 3,4-dihydro-2H-pyrrole derivatives γ，δ-不饱和酮O-(对氰苯基)肟光化学转化为3,4-二氢- 2h -吡咯衍生物

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-06-01 DOI: 10.1016/S1387-1609(01)01254-3

Tetsuhiro Mikami, Koichi Narasaka

引用次数: 0

Is the trinuclear complex the true reducing species in the Cp2TiCl2/Mn- and Cp2TiCl2/Zn-promoted pinacol coupling? 在Cp2TiCl2/Mn-和Cp2TiCl2/ zn促进的pinacol偶联中，三核配合物是真正的还原物质吗?

Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry Pub Date : 2001-06-01 DOI: 10.1016/S1387-1609(01)01259-2

Rasmus J Enemærke, Gitte H Hjøllund, Kim Daasbjerg, Troels Skrydstrup

引用次数: 4