Indanes, heterocyclic

These particular properties of chloroalanes favor the formation of simple Lewis acid-base adducts, as was observed for the reaction of R2AICI with Sb(Tms)3 (R = Et, f-Bu). In contrast, reactions of the analogous gallanes and indanes yielded the desired heterocycles. The same tendencies were observed in reactions of R2MCI (M = Al, Ga, In R = Et, i-Bu) with P(Tms)3 and As(Tms)3. The gallane and indane react under formation of the expected M—E heterocycles [71], while the corresponding alanes yield the simple adducts... 

In 1988, Cowley et al. demonstrated this specific reaction to be also useful for the preparation of heterocyclic stibinogallanes and -indanes.77a,77b [Cl2GaSb(/-Bu)2]3 44 and [/-Bu2Sb(Cl)In-p-Sb(/-Bu)2]2 57 were obtained by reaction of MC13 and /-Bu2SbSiMe3 (see also Scheme 5) and structurally characterized by single crystal X-ray diffraction. In 1996, we and Wells... 

Scheme 7. Synthesis of heterocyclic stibinogallanes and -indanes by dehalosilylation reaction.

Heterocyclic stibino- and bismuthinoalanes, -gallanes and -indanes adopt structures in the solid state analogous to those observed for the corresponding amides, phosphides and arsenides. Their central structural parameters are summarized in Table XVIII. 

Wells et al. reported almost twenty years ago on the reactions of chloro-gallanes and trimethylsilyl-substituted arsanes R 2AsSiMe3, which occurred under elimination of MesSiCl and subsequent formation of arsinogallanes of the types [Cl2GaAsR 2]%> RGa(AsR2)2 and Ga(AsR2)3 [23]. In 1988, Cowley et al. extended this reaction type to the synthesis of heterocyclic stibinogal-lanes and -indanes [21]. 

Tables Heterocyclic stibinogallanes and -indanes of the type [R2MSb(SiMe3)2]x (M = Ga, In) synthesized by dehalosilylation reaction...

Experimental Thermochemistry of Heterocycles and Their Aromaticity A Study of Nitrogen, Oxygen, and Sulfur Derivatives of Indane and Indene... 

We will take a semiempirical approach using numerous molecules, models, assumptions, and estimates rather than doing new calorimetric experiments and/or quantum chemical calculations. Indeed, we will also test what is probably the simplest assumption - that (4n + 2) n electrons found within a conjugated ring species is expected to result in enhanced stability and that this compound is called aromatic. We will consider the dihydroindene (indane) skeleton composed of a benzene ring fused to a nonaromatic five-membered ring that lacks additional double bonds, and will use this carbocyclic hydrocarbon with X = Y = Z = CH2 as a paradigm for many heterocyclic derivatives for which the possible aromaticity is of relevance to the current chapter. Similarly we use indene with -X-Y- = -CH=CH-, Z = CH2 for a variety of unsaturated heterocycles of interest here. 

Keywords aromaticity, indane, indene, nitrogen-containing heterocycles, oxygen-containing heterocycles, sulfur-containing heterocycles, thermochemistry... 

This reaction is essentially thermoneutral. Although we lack enthalpy of formation data for the corresponding 1,3-benzodithiole, the weakness of 1,3 sulfur-sulfur interactions as manifest by the near equality [52] of the enthalpies of formation of 1,3- and 1,4-dithiane (unlike 1,3- and 1,4-dioxane) suggests no special interaction in this nonaromatic heterocycle. Said differently, the thermoneutrality of the above reaction, as opposed to profound exothermicity (21 kJ mol ) for indane (six n electrons) and the endothermicity (29 kJ mol1) for benzimidazolinone (ten n electrons), suggests phenylene trithiocarbonate (ten n electrons) has an intermediate degree of aromaticity. For the latter two species, analysis of the related reactions ... 

Consider now the enthalpies of formation of our diverse indane heterocycles and corresponding one-ring species formed by de-benzoannelation (Table 1). De-benzoannelation resulting in aromatic one-ring species is generally more favorable than processes involving non- or antiaromatic species. The enthalpy of formation difference for aromatic species is typically 50-60 kJ mol-1, for nonaromatic species typically ca. 30 kJ mol-1, and for antiaromatic species ca. 24 kJ mol-1. The difference of the enthalpies of formation between the benzoannelated and one-ring dithiol-2-thiones is —11 kJ mol-1. No explanation for this discrepancy is apparent. 

Finally, we note that all of the discussed heterocyclic derivatives of indane and indene have heteroatoms only in their five-membered ring. There are many other heterocycles related to indane that have the heteroatoms located elsewhere. However, the thermochemistry of such species is essentially uncharted. The enthalpy of formation of purine (XLVIII), with its four nitrogens dispersed through both rings, has been measured in recent times [78], and chronicled in the archive [15] with yet a later value [79], These two values inexplicably differ by over 2000 kJ mol-1. In the absence of a value for the enthalpy of sublimation we are hesitant to discuss this species further, other than to note two estimates from a paper more than 100 years old [80] that straddle the results in [78] by ca. 20 kJ mol-1. 

Tobe and coworkers have extended their work to the pyridine-based cyclophynes 17 and 18 in efforts to detect the incorporation of heteroatoms into the fullerene structure [39]. Similar to the behaviour of the hydrocarbon 16, heterocyclic 17 and 18 show the successive loss of indane units and hydrogen under the conditions of LD mass spectrometry (negative ion mode) culminating in the observation in both cases of the formation of the anion C5gN2. The relative low intensity of the diazafullerene anion observed can be attributed to the kinetic and thermodynamic instability of the heterocage formed. 

The intramolecular carbolithiation of carbon—carbon double bonds is an interesting route to functionalized carbocyclic and heterocyclic systems that has been developed in the past years and widely used in organic synthesis. In this context, aryllithiums have been described to carbometalate double bonds allowing the preparation of indanes,... 

Bidentate N-heterocyclic carbene complexes of group 13 hydrides have been reported recently. Treatment of carbene (31) with two equivalents of [MH3(NMc3)] (M = Al, Ga, In) or LilnTLi (equation 4) resulted in the formation of the 1 2 adducts (32-34). The Al and Ga analogues are moderately thermally stable (dec. 122-124 and 168-171 °C) but less stable than compounds (21-24) and (26). In contrast, the indane adduct (34) decomposes at 10 12°C. The stmctures of (32) and (34) were determined and found to be isostructural. Both (32) and (34) are monomeric and the bidentate carbene ligand (31) bridges two MH3 fragments in a similar manner to bisphosphine complexes. 

A - sulfm-containing heterocycles on the basis of benzo/v/thiophen (I-IX) B - indan-carbazole-sulfoanilide (X-XXX) ... 

Centropolyindanes constitute a complete family of arylaliphatic polycyclic hydrocarbons containing several indane units. Mutual fusion of the five-membered rings leads to three-dimensional, carbon-rich molecular frameworks bearing a central carbon atom, such as benzo-annelated [3.3.3]propellanes, triquinacenes, and [5.5.5.6]- and [5.5.5.5]fenestranes. In this review, the structural concept of centropolyindanes is contrasted to other fused indane hydrocarbons. Besides the syntheses of the parent centropolyindanes and recently described related indane hydrocarbons, the preparation of a large variety of bridgehead and arene substituted centropolyindanes is presented including strained, heterocyclic, and centrohexacyclic derivatives. In appropriate cases, the particular reactivity and some structural features of these unusual, sterically rigid polycyclic compounds are pointed out. 

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