Interactions transannular

Azocin-2( 1H )-one, hexahydro- 1-phenyl-photochemical rearrangement, 7, 656 Azodn-2( 1H )-one, 1,2,7,8-tetrahydro-synthesis, 7, 662 Azocin-5-one IR spectra, 7, 16 transannular interactions, 7, 14 Azocin-5-one, l-(2,4-dimethylphenyl)-IR spectrum, 7, 657 Azocin-5-one, methoxycarbonyl-synthesis, 7, 657 Azocin-5-one, 1-methyl-IR spectrum, 7, 657 synthesis, 7, 657 Azodn-5-one, 1-p-tolyl-IR spectrum, 7, 657 Azocinones... 

Transannular interactions in macroheterocycles including two chalcogen atoms 97YGK1006. 

Of the 24 lines expected for coupling between V (I =7/2) and two equivalent C (I = V ) nuclei, 18 were resolved in the epr spectrum of VO(S CNEt2)2, showing that the C(2s) orbital can also participate in transannular interactions (61). [Cp2V(S2CNEt2)BF4] and dithiophos-phate have been used in an extension of studies on the C4V oxovana-dium(IV) chelates to yield C2V bis(cyclopentadienyl) complexes. 

Transannular interaction via the electron-delocalization mechanism was found, but lessened by 10-15% for the ligand superhyperfine splitting and 30-35% for the hyperfine splitting (62) in the epr spectrum. The crystal structure of [VOS2CNEt2)2] shows that the molecular core has the expected C2V symmetry [V-0 = 159.1(4), V-S = 138.7(2)-241.0(2) pm] (63). Magnetic and spectral data provided evidence for a tetragonal, pyramidal structure (VII) for these complexes. Like many other coordinatively unsaturated, metal... 

Transannular interactions lead to ring closures and reductions to adamantane compounds when dienes of the bicyclo[3.3.1]nonane family are treated with Brpnsted acids and triethylsilane. Compounds 48-51 form reaction mixtures containing various amounts of products 52-54 (R = OH, O2CCF3, Cl) under such conditions.243 The best yields of hydrocarbon 52 occur when the dienes are treated with a 25% excess of sulfuric acid and a 50% excess of triethylsilane in dichloromethane at 20°.243 The stereospecific nature of these transannular reductions is demonstrated by the observation that the enantiomeric purity of the chiral diene 55 is retained in the chiral hydrocarbon product 56 (Eq. 98).243 Dienes of... 

In this chapter, we demonstrated that the restriction of building a compound with only one type of an element is not a restriction at all and a multitude of neutral, cationic as well as anionic polychalcogen structures is currently known. As expected for the more electronegative nonmetal (S) and meta metals (Se, Te), the bonding within these moieties is covalent and a small number of interactions, namely, p2-rap2 lone pair repulsion, n- and n -n bonding as well as p2- cr interactions, are sufficient to rationalize the structures and account for the bond lengths alternations or weak transannular interactions that are often found. 

Most easily oxidized bis-sulfides can be transformed to S- S dications by concentrated sulfuric acid. According to the ESR data,52 dissolving 25 in sulfuric acid establishes equilibrium between the starting sulfide 25, dication 27 and radical cation 26.52 Oxidation of sulfide 29 to a dication 30 by sulfuric acid is facilitated by transannular interaction of the positively charged sulfur atom with the double bond (Scheme 9).53... 

Monosulfoxide 48 where the transannular interaction of the sulfur atoms is minimal also reacts with triflic anhydride to give a white precipitate of highly strained disulfonium dication 49, which is extremely difficult to isolate.71 Dication 49 exhibits only one 1H NMR signal as a singlet at 3.80 ppm in agreement with a symmetric monomeric structure.71... 

The only non-octahedral hexanuclear cluster units are six-membered ring Rh6 (chair conformation, Figure 3), and open, non-planar zigzag chain Zr6, which are found respectively in Rh3S4 and Zr3Te (Rh-Rh 2.70 and 2.87 A Zr-Zr 3.01-3.15 A). In addition there are strong transannular interactions in the Rh6 ring (3.09 A), and weak contacts between the Zr6 chains.96,97... 

This result suggests that in the anodic oxidation of type B, the cation radical formed from one of the two double bonds is stabilized through transannular interaction with another double bond. 

As shown in Table 6 and Figure 1, the oxidation potentials of 2-substituted norbornadienes (1), 2-substituted bicyclo[2.2.2]octa-2,5-dienes (2) and 4-substituted [2.2]paracyclophanes (3) clearly indicate that the transannular interaction between two double bonds contributes already at the stage of the first electron transfer. Namely, in compounds 1-3, the electron is transferred from the unsaturated bond which is not substituted by the electron-withdrawing group, Figure 1 shows the... 

In addition to the major classes of homoaromaticity considered so far, in which the cyclic conjugated array is interrupted by a saturated linkage(s), there is another class of homoaromaticity. In this class a regular cyclically conjugated system is perturbed by homoconjugation(s) [transannular interaction )] (Scott, 1986). This latter class is exemplified by the bridged annulenes. 

The electronic and photoelectron spectra of these types of molecules can only be rationalized in terms of appreciable transannular interactions. The transannular resonance integral has been estimated to be about 40% of that between adjacent p orbitals in benzene. It would seem, therefore, that [130] is more correctly referred to as homonaphthalene and [131] as homoanthracene , etc. It is of interest to note that our probes for homoaromaticity correctly discern the importance of homoconjugation in [130] (Williams et al., 1988). Similar significant transannular interactions are also evident in homoazulene [133] (see Scott et al., 1985 Scott, 1986). 

F. Transannular Interaction of amino Groups with Other Functional Groups... 

Also, the transannular interactions between amino and carbonyl groups in aminoke-tones, like 40-44, were studied by PES48. Pronounced stabilization of the n orbital and destabilization of the no orbital was established by comparison of the relevant ionization potentials with those of the corresponding monofunctional compounds. The shift of the no orbital was noticed as the best indicator of transannular n /jiQ=Q interaction and the maximum value was again found for the system with an eight-membered ring (41). 

In this context transannular interactions must be mentioned, although there are very few authenticated reports of such effects, and they involve solely sp2 carbon atoms. Thus, Maciel and Nakashima (256) ascribed a shielding of the carbonyl atom in 129 of approximately 10 ppm relative to 128 (X = CH2, O, S) to a transannular interaction associated with a partial charge separation (Scheme 40). Less clear-cut results were obtained from the spectra of 3- and 4-thiacyclohexanone (199,257). For the sake of completeness we note that aromatic carbon atoms experience considerable deshielding (6-9 ppm) in bi- and multilayered [2.2]paracyclophanes (258,259). This was attributed to a decrease of the excitation-energy term in the o-p expression (eq. [3], p. 222). 

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