Indene, structure

Alkenyl Fischer carbene complexes can serve as three-carbon components in the [6 + 3]-reactions of vinylchro-mium carbenes and fulvenes (Equations (23)—(25)), providing rapid access to indanone and indene structures.132 This reaction tolerates substitution of the fulvene, but the carbene complex requires extended conjugation to a carbonyl or aromatic ring. This reaction is proposed to be initiated by 1,2-addition of the electron-rich fulvene to the chromium carbene followed by a 1,2-shift of the chromium with simultaneous ring closure. Reductive elimination of the chromium metal and elimination/isomerization gives the products (Scheme 41). 

For a given type of hydrocarbon, coke deposition from re-paraffins displays a minimum for re-heptane from aromatics coke deposition increases for side chain with the possibility of forming a five-carbon ring (indenic structure) for naphthenes the coke deposition is higher in the case of five-carbon atoms rings (95,97). 

In this section the rosins and rosin derivative resins, coumarone-indene and hydrocarbon resins, polyterpene resins and phenolic resins will be considered. The manufacture and structural characteristics of natural and synthetic resins will be first considered. In a second part of this section, the characterization and main properties of the resins will be described. Finally, the tackifier function of resins in rubbers will be considered. 

Fig. 10. Chemical structure of components in coumarone-indene resins.

The struetural element of a eoumarone-indene resin is relatively similar to that for aromatie hydroearbon resins, as they differ only in the proportion of indene-type struetures which are present in higher eoneentration in the eoumarone-indene resins. The main monomers in the aromatie resins are styrene and indene. Styrene produces the atactic conformation of the resins, whereas indene introduees rigidity into the polymer chain. A typical structural element of an aromatie resin is given in Fig. 11. 

A further source of C9 material is coal tar. Structures of the two resins precursors are roughly similar, except the presence of small quantities of coumarone in coal tar feedstream. There is a significant difference in the concentrations of individual monomers coal-tar-based raw material is richer in indene (styrene/indene ratio =1 7) than the petroleum-based feedstream (styrene/indene ratio =1 1). 

The low order of structural specificity required for classical antihistaminic activity was noted earlier. It has been found possible to substitute an indene nucleus for one of the two aromatic rings that most of these agents possess. The basic side chain may be present as either dimethylaminoethyl or itself cyc-lized to provide an additional fused ring. 

In his pioneering work, Sus (1944) assumed that the final product of photodediazoniation of 2,1-diazonaphthoquinone (10.75) is indene-l-carboxylic acid (10.79, not the 3-isomer 10.78). He came to this conclusion on the basis of some analogies (in addition to an elemental analysis). Cope et al. (1956) as well as Yates and Robb (1957) found that the infrared spectrum of the product was consistent with an a,P-unsaturated acid. Later, Melera et al. (1974) verified the structure 10.78 by H NMR spectroscopy. Friedrich and Taggart (1975) showed that the equilibrium between 10.78 and 10.79 at 233 K lies on the side of the latter, but 10.78 clearly predominates at or above 0°C. Ponomareva et al. (1980) showed that not only 2,1-, but also 1,2-diazo-naphthoquinone yields indene-3- and not -1-carboxylic acid. 

The unconventional structure of fulvenes with a unique C=C bond conjugation leads to unusual cycloaddition reactions with other unsaturated systems. For example, alkenylcarbene complexes react with fulvenes leading to indanone or indene derivatives which can be considered as derived from a [6S+3C] cycloaddition process [118] (Scheme 72). The reaction pathway is well explained by an initial 1,2-addition of the fulvene to the carbene carbon followed by [1,2]-Cr(CO)5-promoted cyclisation. 

A chiral indene derivative, structure K, has been most commonly used.222 The catalyst interacts with the trialkylaluminum to generate a bimetallic species that is the active catalyst. 

The reaction of acyclic ADC compounds with monoenes has already been discussed in Sections III,B and IV,B. In certain cases the major reaction pathway involves addition of the ADC compound as a 47r component, to the monoene to give 1,3,4-oxadiazines (Scheme 1). 1,3,4-Oxadiazines are the major or sole products from the reactions of ADC compounds with indene,80 and 4-nitrophenyl vinyl ether,90 and from the reaction of azodibenzoyl with enamines and enol ethers.91 93 Norbornadiene also gives a 1,3,4-oxadiazine (42) with ADC compounds.82 However, benzonorbornadiene behaves differently, and the major product from the reaction with PTAD has the structure 119.205 Other bicyclic monoenes react similarly.206 1,3,4-... 

Because of its great reactivity PTAD has found wide use in the interception of reactive, unstable dienes. For example, unstable isoindenes,226 3a//-indenes,146 1,3-divinylallenes,227 and benzene oxides228 have all been successfully trapped with PTAD. 4-(4-Bromophenyl)-l,2,4-triazole-3,5-dione (5, R = 4-Br—C6H4) is often used if the derivatives ai e required for X-ray structure determination.229 Azodicarboxylic esters have been used to trap tetra(trifluoromethyl)cyclobutadiene,230 and spiro[4.4]nonatetraene.231... 

Figure 30 The structure of the ansa-magnesocene Me2Si(2-Me-tetrahydrobenz[e]inden-3-yl)Mg(THF)2 59.

The crystal structure for 179b was determined which showed a planar geometry for the silver center and the carbaporphyrin ligand. A small tilt angle of 5.09° for the indene unit relative to the mean macrocyclic plane was determined, and the Ag-C bond length was 2.015(4) A. Extension of the work to the benzocarba-, benzi-, oxybenzi-,... 

Depending on the nature of the substrates, selectivity could be completely reversed between the two isomeric products. For example, switching R1 group between Buc and Ph gave high yields of the first and second product structures, respectively. The authors noted that the reaction did not proceed if the imine contained an ortho-MeO group at R2 or if the imine was replaced with an aldehyde, oxime, or hydrazone. The catalytic cycle is initiated by C-H activation of the imine, that is, the formation of a five-membered metallocycle alkyne insertion affords the intermediate drawn in Scheme 69. It is noteworthy that this is the first report of catalytic synthesis of indene derivatives via a C-H insertion mechanism (C-H activation, insertion, intramolecular addition). 

Even Staudinger (89) assigned cyclic structures to poly-indene and polystyrene. He visualized that these polymers would be stretched out into double threads with closed ends in which the two halves of the ring would lie parallel. He called this his "bifilar" hypothesis. 

By the presence of cyclic monomer units obtained, for example, from cyclic olefins (benzofuran, indene, etc.) (58, 254). The erythro- and threo-diisotactic stractures (26, 27 or in a different representation 77, 78) are chiral. If B is equal to A (cyclobutene or analogous monomers) only the threo-diisotactic structure 27 is chiral. 

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