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1.
Two types of palladium complexes, cationic and neutral (R)-DABNTf-Pd(CH3CN)2 were examined as chiral catalysts for enantioselective Claisen rearrangement. DABNTf-Pd(CH3CN)2 complex gave high enantio- and anti-diastereoselectivity, and good yield. This Claisen rearrangement should proceed via six-membered boat transition state through bi-dentate coordination to the Pd catalyst.  相似文献   

2.
Nessan J. Kerrigan 《Tetrahedron》2008,64(29):6863-6869
Palladium (II)-catalyzed [3,3] sigmatropic rearrangement of acyclic allyl vinyl ethers delivers 2,3-anti disubstituted pentenal Claisen adducts with high diastereoselectivity. Reaction conditions for circumventing allyl vinyl ether cleavage that had previously plagued catalyzed rearrangement of α-unsubstituted vinyl ether substrates are described. Merging Pd(II) catalysis with the facile access to the Claisen substrates afforded by Ir(I)-catalyzed olefin isomerization provides an expedient procedure for realizing asymmetric anti-selective Claisen rearrangements.  相似文献   

3.
Richa Pathak 《Tetrahedron》2007,63(2):451-460
Trifluoroacetic acid has been discovered to be a highly effective and efficient reagent for the tandem Claisen rearrangement and cyclization reaction to yield 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones from compounds obtained from the SN2 reaction between anilines and acetyl derivatives of Baylis-Hillman adducts of acrylates in the presence of DABCO. In contrast, similar compounds obtained from the acetyl derivatives of Baylis-Hillman adduct of acrylonitrile on treatment with trifluoroacetic acid directly furnish 3-arylmethyl-2-amino-quinoline via tandem Claisen rearrangement, cyclization and isomerization.  相似文献   

4.
Kaori Yagi 《Tetrahedron》2006,62(20):4933-4940
CuCN-catalyzed reaction of the (1R)-isomer of 4-cyclopentene-1,3-diol monoacetate with TBDPSO(CH2)6MgCl produced an SN2-type product regioselectively in high yield. Mitsunobu inversion of the product and subsequent Claisen rearrangement furnished aldehyde with the two side chains, from which the title compounds were synthesized efficiently.  相似文献   

5.
The tetrahedral intermediate 3 has been intercepted during Pd(II)-cycloalkenylation of olefinic enolsilane 1 (R=SiMe2t-Bu). In a related manner, the allyl and crotyl enol ethers 5–8 give with Pd(OAc)2 acetoxy tetrahydrofurans (9, 12, 14, 16), convertible to butyrolactones or furans; competing Pd(II)-mediated Claisen rearrangement was not observed. The intramolecular Pd(II)-cycloalkenylation of the ketene acetal 17 leads to δ-lactones 18 and 19.  相似文献   

6.
Reaction of N,N′-dimethylbenzimidazolyl iodide (A) with Pd(OAc)2 in DMSO gives selectively trans-bis(N,N′-dimethylbenzimidazoline-2-ylidene) palladium(II) diiodide (trans-2) in 77% yield. The selective formation of the trans-coordination isomer and thus the cis-trans rearrangement is driven by the insolubility of trans-2 in DMSO. X-ray single-crystal diffraction analysis and 13C NMR spectroscopy confirm the trans-geometry of the square planar Pd(II) complex. Catalytic studies show that cis-1 and trans-2 are highly efficient in the Mizoroki-Heck coupling reaction of aryl bromides and activated aryl chlorides both in DMF and [N(n-C4H9)4]Br as ionic liquid. The catalytic activities of Pd(II) complexes with N-heterocyclic carbene ligands derived from benzimidazole are comparable to their imidazole-derived analogues.  相似文献   

7.
A number of 4-aryloxymethyl-7-chlorothiopyrano[2,3-b]thiochromen-5(2H)-ones are regioselectively synthesized in 80-85% yield by the Claisen rearrangement of 2-(4′-aryloxybut-2′-ynylmercapto)thiochromen-4-ones in refluxing chlorobenzene for 3 h. These products are then subjected to a second Claisen rearrangement in refluxing N,N-diethylaniline for 6 h to give hitherto unreported pentacyclic heterocycles in 50-55% yield.  相似文献   

8.
The syntheses and spectral (IR, UV-VIS, XPS, and 1H and 13C NMR) characteristics of the rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide (HBMHCTA) are described. The coordination of HBMHCTA to the central metal ion and its intraligand rearrangement in the complex formation of rhodium(III) ions are studied. The structure of the mixed-ligand complex [Pd(H2L)PPh3] is determined by X-ray diffraction analysis.  相似文献   

9.
Treatment of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) afforded N,N-diethyl-2-fluoro-2-trifluoromethyl-4-alkenamides which were formed by the Claisen rearrangement of intermediary 2-alkenyl-1-diethylamino-2,3,3,3-tetrafluoro-1-propenyl ethers. Although (E)-allylic alcohols gave two diastereomeric products in about 1:1 ratio, (Z)-allylic alcohols gave the corresponding product as a single diastereomer.  相似文献   

10.
Reactions of the trans-PdCl2(PPh3)2 precursor with furan-2-carbaldehyde thiosemicarbazone (Hftsc) and thiophene-2-carbaldehyde thiosemicarbazone (Httsc), in 1:1 molar ratios in the presence of Et3N base, removed one Cl and one PPh3 group from the PdII center, and yielded the complexes [Pd(η2-N3,S-ftsc)(PPh3)Cl] (1) and [Pd(η2-N3,S-ttsc)(PPh3)Cl] (2), respectively. However, when a 1:2 molar ratio (M:L) was used, both Cl and PPh3 ligands were removed, yielding the complexes trans-[Pd(η2-N3,S-ftsc)2] (3) and trans-[Pd(η2-N3,S-ttsc)2] (4). Complexes 14 have been characterized with the help of analytical data, spectroscopic techniques (IR, 1H and 31P NMR) and single crystal X-ray crystallography. The thiosemicarbazone ligands behave as uninegative N3,S-chelating ligands in complexes 14. In contrast, pyrrole-2-carbaldehyde thiosemicarbazone (H2ptsc) and salicylaldehyde thiosemicarbazone (H2stsc) invariably formed the complexes [Pd(η3-N4,N3,S-ptsc)(PPh3)] (5) and [Pd(η3–O, N3,S-stsc)(PPh3)] (6), respectively, and the ligands acted as binegative tridentate donors (N4, N3, S, 5; O, N3, S, 6).  相似文献   

11.
6-Aminopenicillanates, or the sulfoxides or the sulfones thereof, were N-acylated in a three-component reaction with an aldehyde and Ph3PCCO to give the corresponding 6-(E-2′-alkenoyl)amides. This domino addition-Wittig alkenation sequence was extended by an additional Claisen rearrangement step in the side-chain in the case of 5g.  相似文献   

12.
The reaction of aromatic Claisen rearrangement of N-(1-methylbut-2-en-1-yl)anilines in the presence of p-toluenesulfonic acid was investigated. N-Tosyl-2-(1-iodoethyl)-3-methylindoline derivatives were obtained; one of them exhibited a cytotoxic activity.  相似文献   

13.
Treatment of propargyl alcohols (1) with hexafluoropropene-diethylamine adduct (PPDA) affords N,N-diethyl-2-fluoro-2-trifluoromethyl-3,4-alkadienamides (2) that are produced by the Claisen rearrangement of intermediary 2-alkynyl 1-(N,N-diethylamino)-2,3,3,3-tetrafluoro-1-propenyl ethers. Starting from propargyl alcohols bearing a triple bond at the terminal position, the corresponding products (2) were formed with a high stereoselectivity.  相似文献   

14.
One of the most intense peaks in the mass spectrum of N-allylaniline is at m/z 106 (97%). High resolution analysis and collision-induced dissociation studies confirm that this peak contains mostly [C7H8N]+ ions having the anilinomethene structure, but also a small contribution is seen from [C8H10]+ ions which result from the loss of the elements of HCN from molecular ions, following an Amino–Claisen rearrangement. The occurrence of a thermal rearrangement in the sample molecules cannot, however, be completely ruled out. Studies on metastable molecular ions of N-allylaniline and collision-induced dissociation of the m/z 106 ions formed from these show that, in the case of molecular ions with energies closer to threshold, the rearrangement reaction competes much more effectively with the direct cleavage reaction.  相似文献   

15.
Progress in the catalytic asymmetric Claisen rearrangement of 2-alkoxycarbonyl-substituted allyl vinyl ether is reported. Application of a more Lewis acidic catalyst, [Cu{(S,S)-t-Bu-box}](H2O)2(SbF6)2, afforded β-chiral α-keto ester with an enantiomeric excess up to 99%. We suggest a highly polarized transition state for the Lewis acid-catalyzed Claisen rearrangement in order to explain the experimental results.  相似文献   

16.
This work describes the synthesis, characterisation and reactivity of new methylallyl Pd(II) complexes that contain bidentate 2-(methylthio-N-benzylidene)anilines as ligands. The reaction of the binuclear complex [(η3-Me-allyl)Pd(μ-Cl)2] with AgBF4 causes the total abstraction of the chloride bridges, with the subsequent formation of an intermediary fragment of Pd(II). This fragment in turn reacts with neutral bidentate 2-(methylthio-N-benzylidene)anilines to give cationic complexes of Pd(II) of general formula [(η3-Me-allyl)Pd(η2-S,N-MeSC6H4NCHC6H4(X)Y)]BF4 [X=H, Y=H (1); X=F, Y=H (2); X=Me, Y=H (3); X=H, Y=Cl (4); X=H, Y=Me2N (5); X=H, Y=NO2 (6)]. The new complexes were characterised by means of elemental analysis, IR, NMR [1H, 19F{1H}, 13C{1H}, 31P{1H}, Dept, 1H-1H-COSY, HSQC, HMBC] and mass spectroscopies. The reaction of the Pd(II) complexes with nucleophiles such as NaI, (EtO)2PS2K, KCN, KSCN or NaH lead to the deco-ordination of the bidentate ligands to give dimeric or polymeric complexes of Pd(II). The reactivity pattern observed is discussed by a theoretical analysis based on Fukui functions.  相似文献   

17.
Mononuclear palladium-hydroxo complexes of the type [Pd(N-N)(C6F5)(OH)] [(N-N)=2,2-bipyridine (bipy), 4,4-dimethyl-2,2-bipyridine (Me2bipy), or N,N,N,N-tetramethylethylenediamine (tmeda)] react with silanols HOSiR3 in toluene giving the corresponding siloxo complexes [Pd(N-N)(C6F5)(OSiR3)]. The X-ray crystal structure of [Pd(tmeda)(C6F5)(OSiPh3)] has been determined. In one of the two molecules in the asymmetric unit there is an intramolecular interaction by phenyl-pentafluorophenyl π-stacking.  相似文献   

18.
The palladacycle [Pd(μ-O2CMe){κ2C,N-4-MeC6H3N(Me)NO}]2 readily undergoes bridge cleavage reactions with a variety of compounds containing donor functionalities including thioamides, 8-hydroxyquinoline, thioureas, selenoureas, acetylacetone derivatives, dithiocarbamates, xanthates, as well as bidentate N-donors to afford either the monomeric, neutral Pd(II) complexes [Pd{κ2C,N-4-MeC6H3N(Me)NO}{L-L}] or the monocationic complexes [Pd{κ2C,N-4-MeC6H3N(Me)NO}(N-N)]PF6 in high yields. A series of 15 different complexes was prepared and fully characterised spectroscopically and, in some cases, by X-ray diffraction. It was also found that the dithiocarbamato complex undergoes a disproportionation reaction in solution to give the bis(cyclometallated) complex [Pd{κ2C,N-4-MeC6H3N(Me)NO}2] as well as the bis(dithiocarbamato) complex [Pd{κ2S-S2CNEt2}2].  相似文献   

19.
Jin Yang 《Tetrahedron》2019,75(14):2182-2187
A series of mixed N-heterocycles/N-heterocyclic carbene palladium(II) allyl complexes with general formula [(NHC)Pd(η3-allyl)]2(μ2-N-heterocycles)(BF4)2 were prepared in one pot based on anion metathesis of (NHC)Pd(η3-allyl)Cl complexes and then ligand replacement with N-heterocycles [N-heterocycles?=?pyrazine (pyz), 4,4′-bipyridine (bpy) and trans-4,4′-bipyridylethylene (bpe)]. The solid-state structures shown dinuclear structures with two palladium(II) centers holding together by bridged N-heterocycles. Initially investigation of the obtained complexes as precatalysts for direct CH bond arylation of azoles with aryl bromides was carried out.  相似文献   

20.
Three new heterometallic complexes, [Cu(N-Meim)4Pd(μ-CN)2(CN)2]n (1), [Zn(N-Meim)3Pd(μ-CN)2(CN)2]n (2) and [Cd(N-Meim)2Pd(μ-CN)4]n (3), have been isolated from the reactions of M[Pd(CN)4] (M = Cu(II), Zn(II) or Cd(II)) and N-Meim (N-methylimidazole) with in different molar ratios. All complexes have been characterized by X-ray analyses, vibrational (FT-IR and Raman) spectra, thermal and elemental analyses. The crystallographic analysis reveals that the crystal structures of 1 and 2 are 1D coordination polymer, while 3 presents a 2D network. In the Cu(II) and Zn(II) complexes, two cyanide groups of [Pd(CN)4]2− coordinated to the adjacent M(II) ions and distorted octahedral and square pyramidal geometries of complexes are completed by four and three nitrogen atoms of N-Meim ligands, respectively. The Cd(II) ion is six-coordinate, completed with the two nitrogen atoms of N-Meim ligands in the axial positions and the four nitrogen atoms from bridging cyano groups in the equatorial plane. The most striking features of complexes 1-3 are the presence of obvious C-H?Pd hydrogen-bonding interactions between the Pd(II) and hydrogen atoms of N-Meim ligand. This weak hydrogen bonding plays a crucial role in the architecture of the network polymers. The adjacent chains are held together by C-H?Pd, C-H?π or π?π interactions, forming three-dimensional network.  相似文献   

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