scholarly journals Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

2014 ◽  
Vol 10 ◽  
pp. 2021-2026 ◽  
Author(s):  
Henning Hopf ◽  
Swaminathan Vijay Narayanan ◽  
Peter G Jones
Keyword(s):  
Structural Analysis ◽  
Spectroscopic Data ◽  
Acid Treatment ◽  
Aldol Condensation ◽  
Membered Ring ◽  
X Ray

Under basic conditions 4,5,12,13-tetraacetyl[2.2]paracyclophane (9) cyclizes by a double aldol condensation to provide the two aldols 12 and 15 in a 3:7 ratio. The structures of these compounds were obtained from X-ray structural analysis, spectroscopic data, and mechanistic considerations. On acid treatment 12 is dehydrated to a mixture of the condensed five-membered [2.2]paracyclophane derivatives 18–20, whereas 15 yields a mixture of the isomeric cyclopentadienones 21–23. The structures of these elimination products are also deduced from X-ray and spectroscopic data. The sequence presented here constitutes the simplest route so far to cyclophanes carrying an annelated five-membered ring.

Mononuclear and Binuclear Complexes of Platinum(0) Containing (Alkynyl)phenylsilanes

1999 ◽  
Vol 52 (1) ◽  
pp. 51 ◽  
Author(s):  
Martin A. Bennett ◽  
Christopher J. Cobley ◽  
David C. R. Hockless ◽  
Thomas Klettke
Keyword(s):  
Spectroscopic Data ◽  
Chair Conformation ◽  
Membered Ring ◽  
Binuclear Complexes ◽  
Nickel Compound ◽  
X Ray ◽  
X Ray Crystallography

Reaction of bis(cycloocta-1,5-diene)platinum(0) with the (alkynyl)phenylsilanes Ph3SiC2But, Ph2Si(C2But)2 and PhSi(C2But)3 gives, respectively, [Pt (Ph3SiC2But)2] (1b), [Pt {Ph2Si(C2But)}]2 (2b), and [Pt {PhSi(C2But)3}]2 (4b), which contain zerovalent platinum atoms coordinated by two alkyne units. Spectroscopic data indicate that (2b) and (4b) contain two PtC4 and two SiC4 tetrahedra joined at the corners. X-Ray crystallography shows that complex (4b) is isostructural and isomorphous with the known nickel analogue, two of the alkyne units being uncoordinated; the central eight-membered ring comprising two silicon, four alkyne carbon and two platinum atoms has an approximate chair conformation. In contrast, the monomer (1b) is isostructural but not isomorphous with the analogous nickel compound (1a); in the crystal there is evidence for a weak intramolecular phenyl-phenyl interaction.

Diborylverbindungen als Liganden in Metallkomplexen, III Synthese und Struktur von Bis(2.5-dimethyl-3.4-diäthyl-1.2.5-thiadiborolen)-nickel(0) / Diboryl Compounds as Ligands in Metal Complexes, III Synthesis and Structure of Bis(2,5-dimethyl-3,4-diethyl-1,2,5-thiadiborolene)-nickel(0)

1976 ◽  
Vol 31 (2) ◽  
pp. 203-207 ◽  
Author(s):  
Walter Siebert ◽  
Roland Full ◽  
Carl Krueger ◽  
Yi-Hung Tsay
Keyword(s):  
Structural Analysis ◽  
Metal Complexes ◽  
Title Compound ◽  
Spectroscopic Data ◽  
Nickel Complex ◽  
Unit Cell ◽  
Space Group ◽  
X Ray ◽  
Sandwich Compound ◽  
Electron Donating Groups

2,5-Dimethyl-3,4-diethyl-1,2,5-thiadiborolene (1) and Ni(CO)4 yield yellow 1 • Ni(CO)2, which is converted to the corresponding bis( 1,2,5-thiadiborolene)-nickel(0), the first thermostable thioborane nickel complex. Spectroscopic data indicate a pentahapto sandwich compound with the electron-donating groups in approximately tetrahedral arrangement. This is confirmed by X-ray structural analysis. The title compound crystallizes in the space group p21/c with α = 19.594(2), b = 11.8593(4), c = 9.3736(3) Å, β = 102.848(6)° and four molecules per unit cell.

Darstellung und Kristallstruktur der Cäsium-Selenidogermanate(IV) Cs4Ge4Se10 · 2CH3OH und Cs4Ge2Se8 / Preparation and Crystal Structure of the Cesium Selenidogerm anates(IV) Cs4Ge4Se10 · 2CH3OH and Cs4Ge2Se8

1994 ◽  
Vol 49 (5) ◽  
pp. 655-659 ◽  
Author(s):  
W. S. Sheldrick ◽  
B. Schaaf
Keyword(s):  
Crystal Structure ◽  
Structural Analysis ◽  
Chair Conformation ◽  
Membered Ring ◽  
The Novel ◽  
X Ray

Methanolothermal reaction of Cs2CO3 with Ge and Se at 190 °C yields Cs4Ge4Se10 · 2 CH3OH and Cs4Ge2Se8, the structures of which have been determined by X-ray structural analysis. The anion [Ge4Se10]4 in Cs4Ge4Se10)·2 CH3OH displays an adamantane-like structure in which four GeSe4 tetrahedra are linked via joint vertices. In con­trast Cs4Ge2Se8 contains the novel dinuclear anion [Ge2Se8]4-, the first example of a selenidogermanate(IV) exhibiting Se2 bridging units. Two GeSe4 tetrahedra are linked in this anion through Se-Se bonds to yield a six-membered ring, which displays a chair conformation and crystallographic C2h symmetry.

scholarly journals Binuclear Ten-Membered Ring Cyclometallated Complexes of Digold(I) and their Reactions with Iodine and Bromine

2004 ◽  
Vol 59 (11-12) ◽  
pp. 1563-1569 ◽  
Author(s):  
Martin A. Bennett ◽  
Suresh K. Bhargava ◽  
David C. R. Hockless ◽  
Fabian Mohr ◽  
Kellie Watts ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Single Crystal ◽  
Structure Analysis ◽  
Membered Ring ◽  
Chelate Complex ◽  
Donor Ligands ◽  
X Ray ◽  
Cyclometallated Complexes

The cyclometallated digold(I) complexes [Au2(μ-2-C6H4CH2PPh2)2] (10) and [Au2(μ-2-CH2C6H4PPh2)2] (11) have been synthesized by the reaction of Li[2-C6H4CH2PPh2] and Li[2-CH2C6H4PPh2], respectively, with [AuBr(PEt3)]. A single crystal X-ray structure analysis of 10 shows the linearly coordinated gold(I) atoms to be separated by 3.0035(9) Å in a puckered ten-membered ring. Both complexes add one mol equivalent of iodine to form initially gold(I)-gold(III) complexes [Au(μ-2-C6H4CH2PPh2)2AuI2] (14a) and [Au(μ-2-CH2C6H4PPh2)2AuI2] (17), which isomerize to the corresponding salts [Au(κ2-P,C-C6H4CH2PPh2)2][AuI2] (13a) and [Au(κ2-P,C-CH2C6H4PPh2)2][AuI2] (16). In 13a the gold(III) cation is planar coordinated by a pair of chelate P-C donor ligands, the phosphorus and carbon atoms being, separately, mutually cis, as shown by X-ray structural analysis. From the reaction of 10 with 2 mol equivalents of bromine, the neutral chelate complex [AuBr2(κ2-P,C-C6H4CH2PPh2)] (15) has been isolated and structurally characterized.

ortho-Ethynyl group assisted regioselective and diastereoselective [2+2] cross-photocycloaddition of alkenes

2021 ◽  
Author(s):  
Xiaofei Xie ◽  
Hong Pan ◽  
Tai-Ping Zhou ◽  
Man-Yi Han ◽  
Pinhua Li ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Radical Addition ◽  
High Ratio ◽  
Membered Ring ◽  
Mechanistic Studies ◽  
Ethynyl Group ◽  
X Ray ◽  
Geometric Isomerization ◽  
Cyano Groups ◽  
High Yields

Abstract A highly regioselective and diastereoselective [2+2] cross-photocycloaddition between the electron-poor and electron-rich/electron-neutral alkenes under visible-light irradiation was developed. In the absence of an external photocatalyst, the substrates 1 and 4 reacted with rigid cyclic alkoxyethenes to generate (cis,cis)-anti-head-to-head heterocoupled [2+2] products in high yields with regiospecificity and good diastereoselectivity. Meanwhile, the reactions of 1 and 4 with (Z)- and (E)-1,2-diphenylethenes yielded the desired products in good yields with a high ratio of d.r. It is important to note that no geometric isomerization of olefins was observed during the reaction. Mechanistic studies and DFT calculations suggested that 1 and 4 having ortho-ethynyl and cyano groups as a self-photocatalyst play a very important role in the reaction and a five-membered ring diradical intermediate (Int1) was formed via an intramolecular radical addition. The obtained regioselectivity and diastereoselectivity were confirmed by X-ray structural analysis of the representative products.

Synthesis and Structure of Eight-Membered Titanium Containing Siloxane Rings

1992 ◽  
Vol 47 (8) ◽  
pp. 1085-1090 ◽  
Author(s):  
Feng-quan Liu ◽  
Hans-Georg Schmidt ◽  
Mathias Noltemeyer ◽  
Cristina Freire-Erdbrügger ◽  
George M. Sheldrick ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Membered Ring ◽  
X Ray ◽  
Ring Compounds

The preparation by different methods of the eight-membered ring compounds (R1XTiOSiR22O)2 is reported: (2: R1=C5Η5, X=Cl, R2=tBu; 3: R1=N(SiMe3)2, X=C1, R2=tBu; 4: R1=C5Me5, X=Cl, R2=Ph; 6: R1=X=NEt2, R2=tBu). The six-membered ring Ph2SiO[OTiC5Me5(Cl)]2 5 is formed together with 4 by the reaction of C5Me5TiCl3 and Ph2Si(OLi)2. Compounds 2 and 4 have been characterized by X-ray structural analysis.

Synthesis and Structure of the Hexaethylcyclohexaarsoxane Complexes [ { M(CO)3} 2{cyclo-(C2H5AsO)6}], M = Cr, Mo, W

1993 ◽  
Vol 48 (8) ◽  
pp. 1069-1074 ◽  
Author(s):  
William S. Sheldrick ◽  
Thomas Häusler
Keyword(s):  
Molecular Structure ◽  
Structural Analysis ◽  
Equatorial Plane ◽  
Spectroscopic Data ◽  
Ring Expansion ◽  
X Ray ◽  
H Nmr ◽  
Ring Form ◽  
Nmr Data ◽  
Hexadentate Ligand

The hexaethylcyclohexaarsoxane complexes [{M(CO)3}2{cyclo-(C2H5AsO)6}], M = Cr, Mo, W, 2-4 have been prepared by the reaction of (C2H5AsO)n with the respective metal hexacarbonyl in toluene and characterized by their IR and NMR spectroscopic data. For 2 the molecular structure was established by X-ray structural analysis. The 12 atoms of the As6O6 ring form a flattened cuboctahedron in which the 6 oxygen atoms lie in the central equatorial plane. Cr(CO)3 groups are coordinated facially by the upper and lower three arsenic atoms. An approximately S6 symmetry is displayed by the Cr2As6O6 core. Average values of respectively 116.3 and 98.9° are observed for the As–O–As and O–As–O angles in the hexadentate ligand. The ΕΙ-MS and 1H NMR data for (C2H5AsO)n suggest that this alkylcycloarsoxane is present in solution as a mixture of species including trimers and tetramers so that a metal assisted ring expansion is required for the formation of 2-4.

Beiträge zur Chemie des Schwefels, 116 [1]Kristall-und Molekülstrukturen von 1.2.4.5-Benzotetrathiepin und 3-Methyl-1.2.4.5-benzotetrathiepin / Contributions to the Chemistry of Sulfur, 116 [1]Crystal and Molecular Structures of 1,2,4,5-Benzotetrathiepine and 3-Methyl-1,2,4,5-benzotetrathiepine

1979 ◽  
Vol 34 (3) ◽  
pp. 426-430 ◽  
Author(s):  
F. Fehér ◽  
B. Engelen
Keyword(s):  
Structure Analysis ◽  
Spectroscopic Data ◽  
Membered Ring ◽  
Molecular Structures ◽  
Methyl Group ◽  
Chair Form ◽  
X Ray ◽  
Crystal And Molecular Structures

Abstract The structures of 1,2,4,5-benzotetrathiepine and 3-methyl-1,2,4,5-benzotetrathiepine were determined by X-ray structure analysis. The constitution of the molecules, which was proposed by way of spectroscopic data, could be verified. The conformation of the seven-membered rings is the chair form. The position of the methyl group in 3-methyl-1,2,4,5-benzotetrathiepine is equatorial with respect to the seven-membered ring. Details of the conformations are discussed. Bond distances and angles are compared with those in other molecules, which have similar structures.

scholarly journals ALDOL CONDENSATION OF N-ALKYLATED-3-ARYL-4,6-DIMETHOXY-7-FORMYLINDOLES AS A GOOD METHOD FOR THE SYNTHESIS OF 1-ARYL-6,8-DIMETHOXYPYRROLO[3,2,1-hi]INDOLE-4-CARBOXYLATES

2010 ◽  
Vol 6 (3) ◽  
pp. 297-303
Author(s):  
Jumina Jumina
Keyword(s):  
Spectroscopic Data ◽  
Aldol Condensation ◽  
Sodium Hydride ◽  
Good Method ◽  
X Ray ◽  
X Ray Crystallography ◽  
Structural Assignment ◽  
Vilsmeier Formylation

Alkylation of 3-aryl-4,6-dimethoxyindole 3a and 3b with methyl and ethyl a-bromoacetates afforded good yields of indol-1-ylacetates 4. Treatment of these indoles 4 with the Vilsmeier formylation reagent gave formylindoles 5 in 54-81 % yield. These formylindole 5 underwent intramolecular aldol condensation when treated with sodium hydride in tetrahydrofuran to give pyrroloindole-4-carboxylates 6 in 30-60 % yield. Structural assignment based on spectroscopic data confirmed the structure of the synthesized pyrroloindoles. In the case of pyrroloindole 6c, the structure of this molecule was also proven by X-ray crystallography data.    Keywords: indole, pyrroloindole, aldol condensation, alkylation, and formylation

scholarly journals Pseudo-polymorphism of Halogen Substituted Tetraaza[14]annulene Complexes

2014 ◽  
Vol 70 (a1) ◽  
pp. C1004-C1004
Author(s):  
Shuhei Ichimura ◽  
Masahiro Saeki ◽  
Yoshinori Tamaki ◽  
Kazuo Miyamura
Keyword(s):  
Crystal Structure ◽  
Structural Analysis ◽  
Single Crystals ◽  
Membered Ring ◽  
Space Group ◽  
X Ray ◽  
Coordination Sites ◽  
The Difference

6,8,15,17-tetramethyldibenzo-5,9,14,18-tetraazacyclotetradecinatonickel (II) (tmtaa) bears strain within its 14-membered ring and is known to adopt saddle-shaped structure. As a consequence, tmtaa has an asymmetric apical coordination sites at both sides of the saddle. Our previous study revealed that the chlorine substituted complex, [Ni(tmtaa-4Cl)] shown in Figure (X = Cl), exhibited pseudo-polymorphism with dichloromethane and chloroform. This behaviour is due to the good affinity between halogen substituents and halomethane solvent. In this study, we grew single crystals of [Ni(tmtaa-4Br)] using various halomethane solvent as crystallization solvents and elucidated the role of the solvents related to the generation of pseudo-polymorprhism. We have succeeded in obtaining two kinds of single crystals 1 and 2 from the same vial container using bromoform. From X-ray structural analysis, 1 and 2 formed twist dimer as with previous report, and are found to include bromoform in their crystal structure. Note that these complexes adopted more distorted saddle-shaped structure than normal tmtaa complexes. The Ni-N4 planes were not planar. The difference of 1 and 2 was the degree of distortion around Ni-N4 plane, and 1 was more distorted than 2. The space group of these complexes were Aba2 and C2/c respectively. The interactions that led to the difference in packing of dimers were CH...π interaction in 1 and π...π interaction in 2.

Sign in / Sign up

Export Citation Format

Share Document