共查询到20条相似文献,搜索用时 15 毫秒
1.
Sengodagounder Muthusamy Chinnakuzhanthai GangaduraiJanagiraman Krishnamurthi Eringathodi Suresh 《Tetrahedron》2011,67(23):4212-4220
Titanium(IV) chloride and silyl reagents mediated regio- and chemoselective ring opening reactions of oxa-bridged piperidinone ring systems were demonstrated. This methodology interestingly undergoes the stereoselective ring opening at the C-O bond of oxa-bridged piperidinone ring systems. Study of TiCl4 with hydride or non-hydride silyl reagents furnished the product with selectivity. This protocol is highly valuable to synthesize a range of stereoselective piperidinones, quinolinones ring systems. 相似文献
2.
Bromophenyl magnesium reagents generated via a Knochel type magnesium-halogen exchange of aryl iodides undergo regioselective ring opening of cyclic primary and secondary N-Boc sulfamidates in good to excellent yields. With secondary sulfamidates the reaction proceeds with clean inversion of the stereochemistry. This protocol complements the ring opening of aziridines with bromophenyl metal reagents and extends its scope to secondary substrates. 相似文献
3.
Stereoselective synthesis of 4'-alpha-carbon-substituted nucleosides has been accomplished through epoxidation of 4',5'-unsaturated nucleosides with dimethyldioxirane (DMDO) and successive SnCl(4)-promoted ring opening of the resulting 4',5'-epoxynucleosides with organosilicon reagents. [reaction: see text] 相似文献
4.
Laëtitia Palais Dr. Chloée Bournaud Dr. Laurent Micouin Dr. Alexandre Alexakis Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(8):2567-2573
meso‐Hydrazines could be desymmetrised by ring‐opening reactions by using various metal catalysts to form substituted cyclopentenes, which have a high synthetic potential. Herein, we report the asymmetric copper‐catalysed ring opening of a range of polycyclic hydrazines with trialkylaluminium reagents and SimplePhos ligands with both high isolated yields and enantioselectivities of up to 95 %. 相似文献
5.
Stable nitrile oxides are added stereospecifically and regioselectively to the carbon carbon double bond of 2-phenyl-4-arylidene-5(4H)-oxazolones resulting spiro-derivatives 3, 5 . The spectral properties of the reaction products are discussed. The cycloadducts give several substituted isoxazolines via an opening of the oxazolone ring with nucleophilic reagents. 相似文献
6.
BF3-etherate promoted alkylation of aziridines with organocopper reagents: a new synthesis of amines
Boron trifluoride etherate promotes nucleophilic ring opening of a variety of substituted aziridines by diorganocopperlithium reagents leading to both primary and secondary amines. 相似文献
7.
Merging catalytic asymmetric acyl halide-aldehyde cyclocondensation (AAC) reactions with ensuing Grignard-mediated ring opening of the derived enantiomerically enriched beta-lactones is presented as a generally useful asymmetric synthesis of beta-disubstituted carboxylic acids. Enantiomerically enriched beta-lactones are subject to efficient S(N)2 ring opening with a variety of copper-modified alkyl Grignard reagents, including highly branched nucleophiles. Considerable structural variation in the lactone electrophile is also tolerated. Phenyl- and vinyl-derived organometallics are not efficient nucleophiles for the ring-opening reactions. 相似文献
8.
A novel ring opening reaction of the benzothiazole system with allylic Grignard reagents is reported. A possible mechanism is presented. 相似文献
9.
Saverio Florio 《Tetrahedron》1984,40(24)
The title benzoxales
react cleanly with allylic Grignard reagents
undergoing ring opening to give good yields of N-diallyl- alkyl-
-aminophenols
. A plausible mechanism is discussed. 相似文献
10.
Jubi John 《Tetrahedron letters》2007,48(40):7225-7227
Azabicyclic olefins undergo facile palladium-catalyzed ring opening with organoindium reagents affording trans-3,4-disubstituted hydrazinocyclopentenes in good to excellent yields. 相似文献
11.
Bos PH Rudolph A Pérez M Fañanás-Mastral M Harutyunyan SR Feringa BL 《Chemical communications (Cambridge, England)》2012,48(12):1748-1750
A highly efficient method is reported for the asymmetric ring opening of oxabicyclic alkenes with organolithium reagents. Using a copper/chiral phosphoramidite complex together with a Lewis acid (BF(3)·OEt(2)), full selectivity for the anti isomer and excellent enantioselectivities were obtained for the ring opened products. 相似文献
12.
Chanh Huynh Fadila Derguini-Boumechal Gérard Linstrumelle 《Tetrahedron letters》1979,20(17):1503-1506
The copper-catalysed ring opening of epoxides and oxetane by Grignard reagents proceeds in good yield under mild conditions. 相似文献
13.
Yu. V. Tomilov I. V. Kostyuchenko E. V. Shulishov O. M. Nefedov 《Russian Chemical Bulletin》1998,47(4):666-668
The reaction of diazocyclopropane generatedin situ with vinyl bromide occurs as regioselective 1,3-dipolar cycloaddition to give 5-bromospiro(1-pyrazoline-3,1′-cyclopropane)
in ∼60% yield. Reactions of the latter with nucleophilic reagents, which can occur both with retention and opening of the
cyclopropane ring, were studied.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 688–690, April 1998. 相似文献
14.
Whereas alkyl lithium and Grignard reagents both at rt and at −80°C thermally react with 3-methylisoxazolo[5,4-b]pyridine giving alkylation and/or isoxazole ring opening products, sodium malonate and sodium boron hydride react only under UV irradiation. Selective trappings of ketenimine or azirine intermediates give an enaminopyridone or two diasteroisomeric spiroaziridinopirydones. Regioselective opening of the aziridine ring with perchloric acid gives 3(1-amino-ethyl)-1H-pyridin-2-one. 相似文献
15.
The development of a novel asymmetric ring opening of bi- and polycyclic hydrazines with aryl organometallic reagents is presented. The application of this reaction to the most simple bicyclic hydrazine 1a gives a straightforward regio- and diastereoselective access to synthetically useful trans 3,4-disubstituted hydrazinocyclopentenes in an enantioenriched form. 相似文献
16.
A highly efficient copper‐catalyzed enantioselective ring opening of oxabicylic alkenes with Grignard reagents has been developed by using chiral spiro phosphine ligands. Excellent trans selectivities, good yields, and high enantioselectivities are obtained for a broad range of Grignard reagents under mild reaction conditions. The catalyst system shows an extraordinary activity and the TON of the reaction reaches 9000. 相似文献
17.
S. Anas 《Tetrahedron》2008,64(41):9689-9697
A facile synthesis of substituted alkylidene cyclopentenes through a palladium catalyzed ring opening of fulvene derived bicyclic hydrazines with various organometallic reagents is described. The products are versatile synthons with multiple points for functionalization and can be used in the synthesis of a number of biologically active molecules. 相似文献
18.
Carlo Bonini Lucia ChiummientoMaria Teresa Lopardo Maddalena PullezFrançoise Colobert Guy Solladié 《Tetrahedron letters》2003,44(13):2695-2697
Differently protected glycidol derivatives (with Bn, TBDPS, TBS and MPM groups) have been tested for regioselective ring opening with vinylmagnesium bromide in order to obtain useful five-carbon functionalised homoallylic alcohols. Careful choice of the reagents and experimental conditions allowed a general access to important chiral synthons for asymmetric synthesis. 相似文献
19.
Kurt H. Pilgram 《Journal of heterocyclic chemistry》1982,19(4):823-828
A new synthesis of 4,4-dialkyl-2-(substituted)phenylsemicarbazides has been developed. The procedure begins with a 5-substituted-3-(substituted)phenyl-1,3,4-oxadiazolin-2(3H)-one, 3 , which is treated with dialkylamine to give a 1-acyl-4,4-dialkyl-2-(substituted)phenylsemicarbazide, 7 . Subsequent base-catalyzed hydrolysis of 7 gives 4,4-dialkyl-2-(substituted)phenylsemicarbazides, 14 , in high yield. With a variety of nucleophilic reagents, the compounds 3 also undergo ring opening. 相似文献
20.
A highly diastereoselective and efficient synthesis of P-stereogenic bulky alkyl and aryl aminophosphines that relies on ring opening of tert-butyl-oxazaphospholidine 2 is described. Ring opening with several organometallic reagents takes place with inversion of configuration at the phosphorus center as it has been demonstrated by X-ray analysis of two ring-opened intermediates. The unprecedented reactivity observed is attributed to the presence of a free NH functionality that facilitates the attack of the organometallic reagent in an S(N)2@P-type process. 相似文献