Hexasubstituted Benzene Research Articles

First stereoselective total synthesis of macrocarpal C: structure elucidation of macrocarpal G

The first stereoselective total synthesis of macrocarpal C is achieved via a coupling reaction of a silyl dienol ether with a novel hexasubstituted benzene chromium tricarbonyl complex as an optically active benzyl cation equivalent, thereby clarifying the identity of macrocarpal C and G.

Properties of hexasubstituted benzenes with one or two nitro groups. Dielectric, DSC, X-ray and Raman studies

Selected hexasubstituted benzenes containing one or two nitro groups and chlorine atoms or methyl groups have been studied in the solid state by means of dielectric, differential scanning calorimetry (DSC), X-ray and Raman techniques. Unknown phase transitions at 223 and 412 K were found in pentachloronitrobenzene (PCNB), and the existence of a rotational phase above 223 K was confirmed with the help of dielectric measurements. In the case of 1,3-dinitrotetramethylbenzene (1,3-DNTMB) and 1,3-dinitrotetrachlorobenzene (1,3-DNTCB) permittivity dispersion in a low-frequency range has not been detected which was interpreted as a lack of rotatory phases in these compounds. No rotational phase in compounds with the angle between the aromatic ring and nitro group planes equal or close to 90° has been found. The crystal structure of 1,3-DNTCB was determined. 1,3-DNTCB crystallizes in P2 1/ c space group with Z = 4 molecules in a unit cell. DSC data for the studied crystals are quoted for the temperatures from 305 K to the melting point. Low-frequency Raman spectra of the studied compounds are presented and discussed.

Investigations of the tetrachlorosilane-ethanol induced self condensations of ketones.

Silicon tetrachloride-ethanol induced self condensation of ketones to yield tri- or hexasubstituted benzenes, can be diverted in a variety of ways, dependent on the steric hindrance of the ketone. A number of examples of cyclic ketone condensations are given, and the surprising result from condensation of propiophenone as compared with acetophenone is presented.

The direct production of tri- and hexa-substituted benzenes from ketones under mild conditions

Treatment of aryl methyl ketones with tetrachlorosilane in ethanol gives good yields of 1,3-5-triarylbenzenes. Triannulated benzenes result from cyclopentanone and cyclohexanone.

Structural investigation on hexasubstituted benzene derivatives. Part 1. The structure of ortho-dinitrotetramethylbenzene

C10H12N2O4 (Mr=224.2) crystallizes in the triclinic system, space groupP¯1 witha=8.327(3),b=8.734(3),c=8.453(3) A;a=63.6(1),β=97.0(1), γ=100.4(1)°;V=541.0(6) A3,Z=2,Dc=1.38 g cm−3,μ(Cu-Kα)=8.7 cm−1, λ=1.5418 A, F(000)=236. Deviation from theoretic geometry of the benzene ring and from planarity is observed in accordance with theσ-electron-withdrawing character of the NO2 groups and the high steric hindrance of the substituents.

Structural investigation on hexasubstituted benzene derivatives. Part 2: The structure of metadinitrotetramethylbenzene and molecular mechanics analysis on meta and ortho derivatives

C10H12N2O4 (Mr=224.2) crystallizes in the monoclinic system, space groupP21/mwitha=15.462(4),b=7.926(3),c=8.972(3) A;β=90.2(1)°;V=1099.5(6) A3;Z=4;Dc=1.35 gcm−3;μ(Cu-Kα)=8.6 cm−1; λ=1.5418 A;F(000)=472. The position of the molecule on a crystallographic mirror plane forces the NO2 plane to be normal to the benzene ring. Theσ-electron-withdrawing character of the NO2 groups induces a deformation on the geometry of the benzene.

Cyclooligiomerization of Alkynlphosphazenes

Abstract The cyclooligiomerization of the alkynl function in alkynlphosphazenes with various organometallic catalysts has been studied. The cyclization of N3P3F5(C≡CPh) with Fe2(CO)q yields a variety of products including the cyclodimer, cyclopentadienone and a unique cyclotrimer all coordinated to the Fe(CO)3 moiety. The cyclotrimerization of N3P3F5(C≡CPh) with CO2(CO)8 affords a dimetallated asymmetric hexasubstituted benzene derivative, C6(C6H5)3(N3P3F5)3. Due to the sterically hindered nature of the molecule, rotamers derived from restricted rotation about the phosphazene-central arene bond have been observed. Their intratransformations have been examined by VT 19F-NMR. Reactions involving CpCO(CO)2 lead to cyclodimer, cyclotrimer and cyclopentadienone products each coordinated to a CpCo fragment. Other organometallic catalysts capable of tetramerizing and polymerizing alkynlphosphazenes have been investigated.

ChemInform Abstract: Electron‐Rich Hexasubstituted Benzene Derivatives and Their Oxidized Cation Radicals, Dications with Potential Triplet Ground States, and Polycations.

AbstractThe new benzene derivatives (IV), (VIII), and (IX) carrying electron‐releasing substituents are synthesized as outlined in the scheme for (IV) and (VIII); (IX) are obtained similarly from the analogue of (VIIa), prepared according to a modified literature procedure.

Electron-rich hexasubstituted benzene derivatives and their oxidized cation radicals, dications with potential triplet ground states, and polycations

Electron-rich hexasubstituted benzene derivatives and their oxidized cation radicals, dications with potential triplet ground states, and polycations

Non‐ionic X‐ray contrast agents: Detection of ambient temperature isomers of congested hexasubstituted benzenes with multipositional hindered rotations

AbstractSerinol amides of triiodoisophthalic acid bearing an acylamino group are non‐ionic x‐ray contrast agents; in addition to the expected isomerism due to hindered rotations around the amide NCO bonds, the atropoisomerism associated with the hindered rotations around the aryl–CO and aryl–N bonds was investigated by 1H and 13C NMR.The assignment of signal multiplicity to the different rotamers in solution for a series of N, N′‐bis[2‐hydroxy‐1‐(hydroxymethyl)ethyl]‐2,4,6‐triiodoisophthaldiamides, 5‐substituted with (hydroxyacetyl)amino (5), S‐(–)‐ (2‐hydroxy‐1‐oxopropyl)amino (6), (hydroxyacetyl)methylamino (7), and S‐(‐)‐(2‐hydroxy‐1‐oxopropyl)‐methylamino (8) groups was approached by interpreting simpler systems such as S‐(–)‐3‐N‐[2‐hydroxy‐1‐ (hydroxymethyl)ethyl]‐5‐[(2‐hydroxy‐1‐oxopropyl)amino]‐2,4,6‐triiodoissophthalmic acid (2) and its corresponding amide 3, or more symmetric molecules such as N,N′‐bis[2‐hydroxy‐1‐(hydroxymethyl)ethyl]‐5‐amino‐2,4,6‐triiodoisopht haldiamide (4).It is shown that it is possible to discriminate between the contributions of the different types of hindered rotations in order to obtain the appropriate, although approximate, free energies of activation. Secondary aryl carboxamides 5‐8 constitute a rare case of aryl–CO hindered rotation detectable at room temperature. Analysis of the NMR data clearly indicates that in 5‐8 the population ratio of the syn and anti families is 1: 1 and also that of the E and Z conformers. In addition, the secondary anilides 5 and 6 show fast rotation around the aryl–N bond and exhibit a conformational preference for the endo isomer only. The tertiary anilides 7 and 8, instead, present the coexistence of the endo and exo forms whose ratio is dependent on the solvent.

Darstellung und Eigenschaften hexasubstituierter Benzenderivate

Preparation and Properties of Hexasubstituted BenzenesHexasubstituted benzenes are of potential interests as polypodands, host molecules and disc‐like molecules. They are prepared by catalytic cyclotrimerization of disubstituted alkynes 1–8 or by nucleophilic substitution of bromine in hexakis (bromomethyl)benzene 9–17. The different methods of preparation were compared. The new hexasubstituted benzenes were characterized by some chemical and physical properties.

Diazadiene als Steuerliganden in der Homogenen Katalyse, VIII [1] Katalytische Trimerisierung substituierter Acetylencarbonsäureester und Isolierung eines Acetylendicarbonsäureester-Diazadien-Nickel(0)-Addukts / Diazadienes as Controlling Ligands in Homogeneous Catalysis, VIII [1] Catalytic Trimerization of Substituted Acetylene Carbonic Acid Esters and Isolation of an Acetylene Dicarbonic Acid Ester Diazadiene Nickel(0) Adduct

Nickel(0) complexes of diazadienes (dad = RN = CR' - CR ' = NR ) catalyse the trimerization of esters of 2-butynoic acid, phenylpropynoic acid and butynedioic acid to give hexasubstituted benzenes with the unsymmetrical esters 2 as the main products. A primary adduct 7 of acetylene dicarboxylic acid dimethyl ester of the type (dad)Ni(alkyne) could be isolated and characterized by 1H NMR, IR and UV spectroscopy. According to their characteristic CT absorption. 7 and its analogues are shown to persist during catalysis as an active species

Reactions of acetylenes with noble-metal carbonyl halides. Part 7. Synthesis and chemical characterization of cationic and neutral tetrasubstituted cyclobutadiene complexes of platinum(II). X-Ray structure of dichloro(η4-1,2-dimethyl-3,4-diphenylcyclobutadiene)-(triphenylphosphine)platinum(II)

cis-[Pt(CO)2Cl2] reacts at 20 °C with 1-phenylpropyne, in non-polar solvents, to give ionic species of the type [Pt2(C4Me2Ph2)2Cl3][Pt(CO)Cl3](1) with the methyl groups of the η4-cyclobutadiene ring in a cis configuration. Analytical and spectroscopic data of complex (1) show that the cation is a dimeric platinum(II) complex with three bridging chlorine atoms; each platinum is also co-ordinated to a tetrasubstituted cyclobutadiene ring. Complex (1) is easily transformed into the corresponding neutral tetrasubstituted-cyclobutadiene derivative [Pt2(C4Me2Ph2)2Cl4](2). Complex (2) reacts with triphenylphosphine to give the monomeric derivative [Pt(C4Me2Ph2)(PPh3)Cl2](5a). Evidence for the formation of the isomer with trans methyl groups for reactions under different conditions is reported; organic by-products, obtained by dimerisation of acetylenes with CO insertion, and hexasubstituted benzene have been isolated. The crystal structure of complex (5a) has been solved by Patterson and Fourier methods from counter data and refined by diagonal least squares to a final conventional R of 0.046 for 4 358 independent observed reflections. Crystals of (5a) are monoclinic, space group P21/c, with unit-cell dimensions a= 10.900(4), b= 23.437(6), c= 13.289(4)A, β= 113.5(5)°, and Z= 4. The crystals contain discrete molecules in which the co-ordination around the Pt atom is distorted tetrahedral. Selected bond lengths (A) are: Pt–Cl(1) 2.425(3), Pt–Cl(2) 2.430(2), Pt–P 2.353(2). The cyclobutadiene ring is asymmetrically co-ordinated to platinum [Pt–C distances in the range 2.116(9)–2.214(8)A]; the C–C bond distances in the ring, which is planar, are equal to within the estimated standard deviations [av. 1.47(1)A].

Cotton-Mouton and Kerr constants of twelve non-dipolar tri- and hexa-substituted benzenes

Measurements of the infinite-dilution molar Cotton-Mouton and Kerr constants of 12 non-dipolar 1,3,5-tri- and hexa-substituted benzenes as solutes in carbon tetrachloride at 298 K are reported. Some of the experimental results are in notable disagreement with earlier determinations made on equipment of much lower sensitivity. Although the magnetic anisotropies derived for the tri-substituted benzenes are concordant with other observed or predicted values, those for the hexa-substituted benzenes are generally very much larger than expected. It is suggested, in explanation, that relatively large and strongly anisotropic atomic polarizabilities may cause the ratio of the static to the high-frequency polarizability anisotropy to be considerably smaller in the hexa-substituted benzenes than in benzene; in addition, there may be significant temperature independent contributions to the magnetic birefringences of these molecules.

An efficient synthesis of hexa-substituted benzenes and the discovery of a novel host conformation for hexakis (β-naphthylthio) benzene

The title host molecule (III) has been synthesised by reaction of hexachlorobenzene with an excess of the sodium salt of β-mercaptonaphthalene in 1,3-dimethyl-2-imidazolidinone (DMEU) as solvent; other hexakis (arylthio)- benzenes, hexakis(phenoxy) benzene (IV), and hexakis (phenylseleno) benzene (V) were prepared analogously from hexahalobenzenes, HMPA being used as solvent in the last case. An X-ray analysis of the channel-type adduct of (III) with 1,4-dioxan as guest reveals a unique host conformation in which the side-chains are not situated alternately above and below the plane of the central benzene ring.

A new approach for the design of inclusion compounds

A new strategy for the design of inclusion compounds is described. The approach is based on the analogy between the hydrogen-bonded hexamer unit present in the clathrates of phenol, quinol, Dianin's compound, and other hydroxyaromatic hosts, and a hexasubstituted benzene. Suitable hexasubstituted benzenes have been prepared, and on recrystallisation from various solvents, a wide range of inclusion behaviour has been found for compounds (I), (III), (VIII)–(XIII), (XV), and (XVIII)–(XX), In addition, several of these hosts, for example, (III), (VIII), (IX), and (XIII), exhibit remarkable guest selectivity properties when recrystallised from solvent mixtures. A detailed X-ray study of the carbon tetrachloride adduct of hexakisphenylthiobenzene (I) has been carried out. The crystals are trigonal, space group R, with a= 14.263; c= 20.717 A, and three host and six guest molecules in the hexagonal unit cell. A true clathrate structure is found and two CCl4 guest molecules fit snugly into a cavity of effective length ca. 17 A, a C–Cl bond of each guest being collinear with the c axis of the crystal.

Komplexe zwischen Neutralmolekülen: Neutralkomplexe von krakenmolekülen mit kronenethern und anderen organischen molekülen

Crown ethers, water and several other neutral molecules are shown to form crystalline, strictly stoichiometric addition compounds with hexasubstituted benzene derivatives. These are suited for systematic investigations of intra- and intermolecular complexation between organic molecules.

Crystal and molecular structure of a ‘hexa-host’ inclusion compound

WE recently suggested1, and found experimental support for1,2, a totally new concept for the design of inclusion compounds. Using this design concept we prepared a series of host compounds based on a hexa-substituted benzene ring (I), and we now report the results of the first X-ray structural study on one of these compounds.

Reaction patterns of cyclopentadienylcobalt(I) carbonyl and acetylene derivatives

Studies have been made of photochemical and thermal reaction sequences through which bisubstituted acetylenes are transformed in (C 5H 5)Co-carbonyl reaction systems into cyclobutadiene and cyclopentadienone complexes and hexasubstituted benzenes. A primary intermediate observed by its IR spectrum in low-temperature photochemical reactions of (C 5H 5)Co(CO) 2 with diphenyl alkynes RCCR is the mixed mononuclear species (C 5H 5)Co(CO)(RCCR). At room temperature this species is converted by excess alkyne into the cyclopentadienone complex (C 5H 5)Co(R 4C 4CO). We have isolated from these reactions systems an important intermediate the mixed binuclear compound(C 5H 5) 2Co 2(μ-CO)(RCCR). In the presence of excess alkyne this compound is thermally converted either to the cyclobutadiene or to the cyclopentadienone complex of (C 5H 5)Co, depending on the partial pressure of CO in the reaction system. The mixed binuclear compound forms a catalyst for the cyclotrimerization of excess 2-butyne. The fluxional binuclear metallocycle (C 5H 5) 2Co 2[(CH 3) 4C 4], which is formed by sodium amalgam reduction of (C 5H 5)Co(CO)I 2 in the presence of 2-butyne, is a true catalyst for alkyne cyclotrimerization.

Correlation of Ionization Potentials and the Sums of Substituent Constants for Substituted Benzenes

Previously reported experimentally determined ionization potentials of substituted benzenes are well correlated by the sum of the para substituent constants, regardless of the orientation of the substituents. σ+ is better than σ for this purpose. Tri-through hexasubstituted benzenes are also correlated, but the slope and intercept are higher in accord with electrostatic theory. These results in support of recent MO calculations indicate that substituent constants are good measures of the energy of the highest occupied orbital.