Transannular Interaction Research Articles

Generation of hexahydroazulenes

( Z)-Cyclodec-1-en-6-yne ( 3) generates three conjugated hexahydroazulenes 3→ 1k→ 1c, 1ℓ under FVP conditions, whereas flash vacuum pyrolysis (FVP) of cyclodecyne ( 2) leads to 1,2,9-decatriene ( 9). We attribute the different thermal behavior of 2 (ring opening) and 3 (ring closure) to different transannular interactions. Altogether 22 constitutional isomers of hexahydroazulene should exist; three new isomers ( 1k, 1ℓ, and 1m) are presented here, ten were described earlier, but the reinvestigation of the dehydration route of bicyclic alcohol 11 showed that one of the ten structures has to be revised.

3層および4層[3.3]パラシクロファンの合成，構造および渡環π-π相互作用

3層および4層[3.3]パラシクロファンの合成，構造および渡環π-π相互作用

Experimental Modeling of Selective Alkene Oligomerization: Evidence for Facile Metallacyclopentane Dehydrogenation Mediated by a Transannular β-Hydrogen Agostic Interaction

Ring-expansion of the zirconacyclopropane (η5-C5Me5)Zr[N(i-Pr)C(Me)N(i-Pr)](η2-CH2CHC6H5) (1) was accomplished through insertion of ethene, propene, and styrene into a metal−carbon bond to yield the series of crystalline zirconacyclopentane derivatives 2−4, respectively, for which solid-state molecular structures have been obtained through single-crystal X-ray analyses. The metallacyclopentane rings of 2 and 4 adopt half-chair conformations that place all β-hydrogens distant from the metal center (cf. nonbonded distances of 3.2−4.0 A). On the other hand, a twisted-envelope conformation for the zirconacyclopentane ring of 3 features a β-hydrogen agostic interaction with the metal center [cf. a Zr1−H21B distance of 2.38(2) A]. Unlike 2 and 4, compound 3 decomposes rapidly in solution at 25 °C to provide the structurally characterized zirconacyclopent-3-ene derivative 5. Ring-expansion of 1 with 1-(trimethylsilyl)ethene directly provides the zirconacyclopent-3-ene derivative 7. A mechanism for this facile me...

Mono- and binuclear complexes of rhodium involving a new series of hemilabile o-phosphinoaniline ligands

Monophosphines of the type Ph(x)PAr(3-x) (x = 0, 1 or 2, Ar = o-N-methylanilinyl) and the diphosphine, Ar(2)PCH(2)PAr(2) (mapm) have been synthesized for use as chelating and/or bridging P,N-ligands within mono- and binuclear rhodium(i) complexes, respectively. The previously prepared phosphines, Ph(x)PAr'(3-x) (x = 0, 1 or 2, Ar' = o-N,N-dimethylanilinyl) and Ar'(2)PCH(2)PAr'(2) (dmapm), have also been used to prepare analogous mono- and binuclear complexes. Variable temperature (1)H NMR spectroscopy of the mononuclear complexes, [RhCl(CO)(L)] (L = PhPAr(2), PhPAr'(2), PAr(3) and PAr'(3)), and line-shape analyses of the resultant spectra indicate the substantially increased lability of the N,N-dimethylanilinyl donors relative to the related monomethylanilinyl groups. X-Ray structural analyses of the mononuclear complexes suggest that the enhanced Type II hemilability in the dimethylanilinyl complexes compared to their monomethyl analogues results from increased steric interactions involving the coordinated dimethylanilinyl substituents. In the case of the binuclear, dmapm-bridged compound [Rh(2)Cl(2)(CO)(2)(micro-dmapm)], there are additional transannular repulsions between the chloro ligand on one metal and the coordinated dimethylanilinyl group on the other, which result in a Rh-Rh separation of over 4.1 A. For the analogous mapm-bridged species, the transannular interactions between the chloro ligands and the amine hydrogens are in fact attractive, resulting in a much closer Rh-Rh separation (3.450 A). The chloride substituents of [Rh(2)Cl(2)(CO)(2)(micro-mapm)] can be replaced to generate the complexes, [Rh(2)(X)(2)(CO)(2)(micro-mapm)] (X = I, CF(3)SO(3), CH(3)CO(2)), the last of which also exhibits pronounced transannular hydrogen-bonding interactions in the solid state.

Novel derivatives of hypervalent germanium: synthesis, structure, and stability

Syntheses of a series of novel germanium complexes, viz. RN(CH(2)CH(2)NC(6)F(5))(2)GeHal(2) (, R = Me, Hal = Cl; , R = Me, Hal = Br; , R = PhCH(2), Hal = Cl; , R = PhCH(2), Hal = Br), as well as MeN[CH(2)(2-C(4)H(3)N)](2)GeHal(2) (, Hal = Cl; , Hal = Br), by the reaction of GeHal(4) with dilithium salts of corresponding triamines are presented. PhCH(2)N(CH(2)CH(2)NSiMe(3))(2)GeCl(2) () was prepared analogously from triamine . Other approaches to the synthesized compounds were also tested. Unexpected complexes [N[upper bond 1 start](CH(2)CH(2)NSiMe(3))(2)Ge[upper bond 1 end](Hal)](2) (, Hal = Cl; , Hal = Br) were obtained by the reaction of GeHal(4) with dilithium salt of Me(3)SiN(CH(2)CH(2)NHSiMe(3))(2) (). DFT calculations on this reaction were carried out and discussed. Composition and structures of the novel compounds were established by elemental analyses, (1)H, (13)C, and (19)F NMR spectroscopy. The X-ray structural studies of and clearly indicated the presence of a transannular interaction N(ax)-->Ge for all studied compounds.

Hexacoordinated spirocyclic germanium(IV) complex: Synthesis and structural characterization

AbstractThe spiro‐dibenzogermocine [O(o‐C6H4S)2]2Ge (1) was prepared in a reaction between O(o‐C6H4SH)2 and Ge(OiPr)4, and its molecular structure was determined by X‐ray diffraction studies. In the solid state, 1 shows the existence of two weak O → Ge transannular interactions, resulting in a hexacoordinated germanium atom that displays the geometry of a distorted bicapped tetrahedron. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:45–49, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20510

Engineering discrete stacks of aromatic molecules

Intrigued by transannular interactions occurring in stacked aromatic molecules, chemists have long endeavored to engineer discrete stacks of specific lengths and orientation. The maturation of self-assembly methodologies has shifted the focus away from utilizing covalent scaffolds to harnessing non-covalent interactions such as ionic interactions, hydrogen bonds, metal-ligand interactions, and aromatic interactions. Aromatic molecules often assemble into ill-defined, infinite aggregates and thus multiple self-assembly techniques must be combined to achieve the desired stack size and conformations. This critical review briefly highlights covalent scaffolds of stack aromatics before focusing on modern self-assembly based strategies for engineering discrete stacks of aromatic molecules (149 references).

Synthesis, characterization and crystal structures of organolead dithiolate compounds displaying transannular interactions D···Pb (D = O, S)

Treatment of Ph 2PbCl 2 with O(C 6H 4SH) 2 ( 1a), S(C 6H 4SH) 2 ( 2a) and S(C 6H 3SH) 2O ( 3a) afforded the stable organolead compounds [{O(C 6H 4S) 2}PbPh 2] ( 1b), [{S(C 6H 4S) 2}PbPh 2] ( 2b) and [{S(C 6H 3S) 2O}PbPh 2] ( 3b). X-ray structure determinations of dithiolate-diphenyl lead compounds 1b– 3b revealed that the trichalcogenated ligands are tridentate in 1b and 2b, and bidentate in 3b. The lead atom acts as an acceptor atom exhibiting weak intramolecular transannular interactions with the donor D atom, with tetrahedral distortions of 48% for 1b, 51% for 2b and 45% for 3b. The local geometry at the lead atom is described as monocapped tetrahedral. The crystal packing of title compounds is stabilized by several non-bonded interactions.

Synthesis and structures of new 1,3,6,2-dioxazaborocanes containing substituents in the ocane fragment

New 1,3,6,2-dioxazaborocanes R1N(CHR3CR4R2O)(CHR6CHR5O)BX (1–11, X = Ph, 4-MeC6H4, Me; R1 = Me, PhCH2; R2, R3, R4, R5, R6 = H, Ph) were synthesized by the reactions of aryl- or methylboronic acids with dialkanolamines. The treatment of (Me2NCH2CH2O)3B (15) with MeN(CH2CH2OH)(CH2CPh2OH) afforded 2-[2-(dime-thylamino)ethoxy]-1,3,6,2-dioxazaborocane (12). 2-Fluoro-1,3,6,2-dioxazaborocanes R1N(CHR3CHR2O)(CH2CH2O)BF (13: R1 = PhCH2, R2 = R3 = H; 14: R1 = Me, R2 = R3 = Ph, threo) were synthesized by the reaction of bis(trimethylsilyl) ethers of the corresponding dialkanolamines with BF3·Et2O. The new borocanes can be used for the synthesis of the corre-sponding germanium derivatives PhCH2N(CH2CH2O)2GeX2 (16, X = OEt; 17, X = Cl), as exemplified by the reaction of compound 6. The structures of erythro-MeN(CH2CH2O)(CHPhCHPhO)BPh (3), threo-MeN(CH2CH2O)(CHPhCHPhO)BPh (4), erythro-MeN(CH2CH2O)(CHPhCHPhO)B(4-MeC6H4) (8), and PhCH2N(CH2CH2O)2BF (13) were established by X-ray diffraction. The coordination polyhedra of the boron atoms in these complexes can be described as distorted tetrahedra. The boron-nitrogen distances (1.705(7)–1.723(3) A) provide unambiguous evidence for the presence of the B←N transannular interaction in these compounds. The structures of the resulting borocanes containing phenyl substituents at the carbon atoms of the ocane skeleton were studied by NMR spectroscopy and quantum chemical density functional theory calculations.

Synthesis and spectral characteristics of silicon-containing poly(salicylidene azomethines) derived from aromatic di- and tetraamines

New silicon-containing poly(salicylidene azomethines) were prepared by polycondensation of di-or tetrasalicylidene derivatives of aromatic di- or tetraamines. The spectral data suggest the occurrence of noncovalent transannular donor-acceptor interaction N→Si providing “nonclassical” conjugation.

Dipole moments, structure, and transannular interactions in silatranes containing planar fragments

The method of dipole moments and theoretical calculations (DFT B3LYP/6-31G*) were used for structural assessment of silatranes N[CH2(RMeC6H2)O]3SiR1 containing planar fragments in the six-membered semirings. They are endo structures with transannular N→Si interaction which involves, along with nitrogen and silicon, oxygen atoms adjacent to silicon.

Synthesis, Structure, and Transannular π−π Interaction of Three- and Four-Layered [3.3]Paracyclophanes

The synthesis of three- and four-layered [3.3]paracyclophanes ([3.3]PCPs) 3-5 has been accomplished by utilizing the (p-ethylbenzenesulfonyl)methyl isocyanide (EbsMIC) method. The structures of the three- to four-layered [3.3]PCPs 3- 5 and their diones 8, 10, and 11 have been elucidated based on the (1)H NMR spectra and finally by X-ray structural analysis. In the three-layered [3.3]PCP-dione 8, the trimethylene bridges of the [3.3]PCP unit assume a chair conformation similar to that of 2, while the [3.3]PCP-2,11-dione unit assumes a boat conformation different from that of [3.3]PCP-dione 1 with a chair conformation. On the other hand, the two [3.3]PCP units in three-layered [3.3]PCP 3 both assume a boat conformation. In the four-layered [3.3]PCP-dione 10, the two outer [3.3]PCP units assume a boat conformation while the inner dione unit has a chair conformation. The trimethylene bridges in the four-layered [3.3]PCP 4 are highly disordered even at -150 degrees C. All the outer benzene rings are distorted into a boat form while the inner ones are distorted into a twist form. In the electronic spectra, bathochromic shift and hyperchromic effect are observed, but the magnitude decreases with an increase in the number of layers and the spectra become structureless. In the charge-transfer (CT) bands of the three- to four-layered [3.3]PCPs 3- 5 with tetracyanoethylene (TCNE), two absorption maxima (lambda(max)) are observed. The effect of an increase in the layers becomes significant, and the changes in the longest wavelength lambda(max) values from two to three and three to four are ca. 60 and 50 nm, respectively. By comparison of the stereoisomeric four-layered [3.3]PCPs 4 (meso) and 5 (racemic), the helical arrangement of the trimethylene bridges of 5 shows a more efficient transannular pi-electronic interaction. In the three- to four-layered [3.3]PCP-diones, a magnitude of the CT interaction almost comparable to that of [3.3]PCP 2 was observed, and this indicates that the -CH(2)COCH(2)- bridges inhibit the CT interaction and that this tendency is supported by the calculated HOMO energy levels and observed oxidation potentials. Three- and four-layered [3.3]PCPs 3- 5 show reversible redox processes, and 4 and 5 show an electron-donating ability almost comparable to that of [3 6]CP. Very good correlation between the lambda(max) of the CT bands with TCNE and the oxidation potentials is observed.

Discreteness of π-conjugation of 1,6-methano[10]annulene by troponoid fusion at the 3,4-positions

The tropone-fused 1,6-methano[10]annulene 4 was synthesized from 3,4-bis(bromomethyl)-1,6-methano[10]annulene and the protonation of 4 provided the hydroxytropylium ion-fused annulene 5. 1H NMR spectra of 4 and 5 exhibited an unequal shielding effect on the bridge hydrogens from the resulted π ring system, suggesting the existence of the significant homoconjugative transannular interaction on the nonadjacent carbons at the bridge and the discreteness of π-conjugation of the annulene between two bonds at the C7–C8 and C11–C12 to localize the C8–11 dienyl and the remaining parts. The X-ray crystallographic structures of 4 and 5 show relatively short atomic distance between those bridge carbons, and clear bond alternation of the dienyl part and the bond convergence of the remaining part in these compounds, supporting the spectral properties.

Pentacoordination at antimony in dibenzostibocines via D–Sb transannular interactions (D = O, S): A structural study

Addition of M 2SCN(CH 2R) 2 to D(C 6H 4S) 2SbCl in methylene chloride solution leaded to the formation of the stable compounds D(C 6H 4S) 2SbS 2CN(CH 2R) 2 (D = O, R = Me, 1; D = S, R = Me, 2; R = Ph, 3). The new dibenzostibocines derivatives containing two different types of dithioligands were characterized by elemental analysis and spectroscopic studies (IR, 1H and 13C NMR). Single crystal X-ray diffraction determinations of complexes 1– 3 revealed that the antimony atom acts as an acceptor atom exhibiting an intramolecular transannular interaction with the donor D atom, expanding its coordination from three to five and displaying a skew trapezoidal local geometry.

Transannular Interactions in Mixed Superphanes with One Thiophene and One CpCo-Stabilized Cyclobutadiene Ring: Syntheses, Structures, and Electrochemistry

Superphanes consisting of one thiophene ring and various substituted RCo-stabilized cyclobutadiene (CBD) rings (R = Cp, C5H4(CH3), C5(CH3)5, C5H4(Si(CH3)3), C5H4(COCH3), 8−12) and one superphane with one thiophene ring and one CpCo-stabilized cyclopentadienone ring (13) were synthesized. The starting point was a tricyclic diyne with a central thiophene ring and two condensed 4-cyclodecynes, 19. Heating of 19 with RCo(COD) yielded 8−12, whereas the heating of 19 with CpCo(CO)2 gave 13. X-ray structural investigation of 8−13 afforded the geometrical parameters in the solid state. Cyclic voltammetry showed a strong interaction between the thiophene ring and the CpCo-stabilized cyclobutadiene part. This interaction was substantiated by comparison between the CV data of 8−12 and model systems containing only the CpCo(CBD) part.

Transient palladadiphosphanylcarbenes: singlet carbenes with an "inverse" electronic configuration (p(pi)2 instead of sigma2) and unusual transannular metal-carbene interactions (piC-->Pd donation and sigmaPd-->C back-donation).

Upon treatment with [PdCl(allyl)]2, asymmetrically substituted alpha,alpha'-diphosphanyl diazo compounds eliminate dinitrogen to afford C-chlorodiphosphanylmethanide complexes in high yields. In the presence of a chloride-abstracting agent, such as sodium tetraphenylborate, the C-chlorodiphosphanylmethanide complexes react with pyridine and trimethylphosphine, readily affording the corresponding nitrogen and phosphorus ylides. The postulated intermediate in this process, namely palladadiphosphanylcarbenes, could not be spectroscopically characterized, but their transient formation was chemically supported further by a Lewis base exchange reaction between pyridine and 4-dimethylaminopyridine. This hypothesis has also been substantiated by computing the corresponding dissociation energy using two model systems featuring methyl groups at the phosphorus. Of particular interest, density functional theory calculations reveal that these palladadiphosphanylcarbenes have a singlet ground state with an "inverse" ppi2 electronic configuration and a distorted geometry associated with unusual transannular metal-carbene interactions (piC-->Pd donation and sigmaPd-->C back-donation).

Effect of transannular interaction on the redox-potentials in a series of bicyclic quinones

BackgroundBetter understanding of the transannular influence of a substituent on the redox-potentials of bicyclo[2.2.2]octane-derived quinones will help in the design of new compounds with controlled biological activity. However, attempts to directly relate the reduction potentials of substituted triptycene-quinones to the electronic effects of substituents are often unsuccessful.ResultsFirst and second redox-potentials of a series of bicyclic quinones are compared to computed energies of their LUMO, LUMO+1, and energies of reduction. Transannular influence of substituent on the redox-potentials is rationalized in terms of MO theory. Acetoxy-substituents in the 5,8-positions of the triptycene-quinone system selectively destabilize the product of the two-electron reduction.ConclusionWe have shown that first redox-potentials of substituted bicyclic quinones correlate with their calculated LUMO energies and the energies of reduction. The second redox-potentials correlate with calculated LUMO+1 energies. As opposed to the LUMO orbitals, the LUMO+1 orbital coefficients are weighted significantly on the non-quinone part of the bicyclic system. This accounts for: (1) significantly larger substituent effect on the second redox-potentials, than on the first redox-potentials; (2) lack of stability of the product of two electron reduction of 5,8-diacetoxy-9,10-dihydro-9,10-[1,2]benzenoanthracene-1,4-dione 5.

Pentacoordination at Germanium by Transannular Bonding of Sulfur or Oxygen in an Eight‐Membered Ring: An Experimental and Theoretical Study

AbstractTreatment of LnGeCl4–n with D(C6H4SH)2 in the presence of nBuLi leads to the formation of the stable compounds D(C6H4S)2GeL1L2 (for D = S, L1 = Cl, L2 = Ph, 1 and L1 = L2 = Ph, 3; for D = O, L1 = Cl, L2 = Et, 4 and L1 = L2 = Ph, 5). The S(C6H4S)2Ge(Ph)Br compound (2) has been synthesised by halogen exchange from 1 and potassium bromide. X‐ray structure determinations of complexes 1–5 reveal that the germanium atom acts as an acceptor atom displaying an intramolecular transannular interaction with the chalcogen D atom. The geometry of the pentacoordinate Ge atom in the title compounds is described as distorted trigonal bipyramidal with a 64–31 % distortion displacement. The D→Ge (D = S, O) hypercoordinate interaction was studied by DFT methods using correlation consistent basis sets and relativistic ECP for Ge. NBO analysis showed that this interaction can be explained in terms of the interplay of covalent and Coulombic interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Chemo-, regio- and stereoselective 1,3-dipolar cycloaddition of C-aryl- N-phenylnitrones over 3,5-bis(arylidene)-1-methylpiperidin-4-ones: synthesis of highly substituted novel spiro-isoxazolidines

1,3-Dipolar cycloaddition of C-aryl- N-phenylnitrones to 3,5-bis-(arylidene)-1-methylpiperidin-4-ones affords novel mono- and bis-spiroisoxazolidines in moderate yields. In general, this reaction predominantly yields mono-spiroisoxazolidine, wherein the oxygen of the nitrone is linked to the β-carbon of the benzylidene moiety, while 3,5-bis-(2-chloro- and 3-nitro-benzylidene)-1-methylpiperidin-4-ones afford predominantly bis-spiroisoxazolidines. The cycloaddition of mono-spiroisoxazolidines occurs with facial diastereoselectivity to furnish bis-spiroisoxazolidines. The nitrogen in the heterocyclic ring of the 3,5-bis-(arylidene)-1-methylpiperidin-4-ones facilitates the cycloaddition through transannular (N⋯C O) and/or homoconjugative (N⋯C C) interactions.

Synthesis, Characterisation and Properties of As‐Monohalogenated Dibenzoarsocines S(C6H4S)2AsHal (Hal = Cl, Br, I) – A Study of the Transannular Interaction S→As

AbstractAddition of AsCl3 to S(C6H4SH)2 in benzene solution leads to the formation of the stable compound S(C6H4S)2AsCl (1). The S(C6H4S)2AsHal [Hal = Br (2), I (3)] compounds have been synthesised by halogen exchange from 1 and the corresponding potassium halide. X‐ray structure determinations of complexes 1–3 reveal that the arsenic atom acts as an acceptor atom exhibiting an intramolecular transannular interaction with the thioether‐like sulfur atom. The geometry of the tetracoordinate As atom in the title compounds is described as distorted pseudo‐trigonal‐bipyramidal with a stereochemically active lone pair and 66–63 % trigonal‐bipyramidal character. The transannular interaction influences the conformation of the dibenzotrithiarsocine system, adopting the central eight‐membered ring with a boat–boat conformation and Cs symmetry.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)