Indene derivatives, formation

The reaction of alkoxyarylcarbene complexes with alkynes mainly affords Dotz benzannulated [3C+2S+1C0] cycloadducts. However, uncommon reaction pathways of some alkoxyarylcarbene complexes in their reaction with alkynes leading to indene derivatives in a formal [3C+2S] cycloaddition process have been reported. For example, the reaction of methoxy(2,6-dimethylphenyl)chromium carbene complex with 1,2-diphenylacetylene at 100 °C gives rise to an unusual indene derivative where a sigmatropic 1,5-methyl shift is observed [60]. Moreover, a related (4-hydroxy-2,6-dimethylphenyl)carbene complex reacts in benzene at 100 °C with 3-hexyne to produce an indene derivative. However, the expected Dotz cycloadduct is obtained when the solvent is changed to acetonitrile [61] (Scheme 19). Also, Dotz et al. have shown that the introduction of an isocyanide ligand into the coordination sphere of the metal induces the preferential formation of indene derivatives [62]. 

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). 

Styrene and indene derivatives (Scheme 2, Y = Ph) are dimerized to l,4-dimethoxy-l,4-diphenylbutanes or 1,4-diphenylbutadienes (Table 7, numbers 1 and 2) [52]. The product distribution is in some cases strongly dependent on the anode potential and the supporting electrolyte. Dimerization is promoted by a-substituents that stabilize the intermediate radical cation, for example, phenyl, vinyl, alkoxy, dialkylamino groups. IJ-Alkyl substituents strongly decrease the yield of dimers and favor formation of dimethoxy-lated monomers. 

Lactone formation on treatment of uneatumted acids with pwox acids ib not confined to the field of fatty acid chemistry. Howell m l Taylor obtained a hydroxylactone, for instance, on adding perfoi nm acid to the indene derivative shown in Eq. 1 106). An epoxide < assumed to constitute the intermediate stage of this transformation. 

Many reactions afford, in addition to the naphthalene derivatives, mixtures of products. One of the major side reactions is the formation of indene derivatives directly from the metathesis intermediate without insertion of carbon monoxide. Other products frequently isolated as minor components are furans, cyclobutanones, and cyclopentenediones. The product distribution is dependent on numerous factors, including solvent, reaction temperature, concentration of the alkyne, and the nature of the aryl substituent. Molybdenum carbenes give, depending on the alkyne, either naphthols or indenes exclusively. The molybdenum Fischer carbenes can be tuned to give naphthoquinones by replacing one of the carbon monoxide ligands with a phosphine (Scheme 45). 

Chlorofluorocarbene generated by phase-transfer catalysis underwent addition to cyclo-pentadiene and indene derivatives to give adducts which rearranged to aromatic compounds, via elimination of hydrogen chloride, e.g. formation of 7. ... 

For the addition of furan and benzofuran to benzocyclopropene, a diradical mechanism has been proposed for the formation of 4. Similarly, AT,At-dimethyl- or A-methyl-A-phenyl-hydrazones of a,/ -unsaturated aldehydes (acrylaldehyde and 2-methylacrylaldehyde) reacted by radical addition at the C-C double bond with benzocyclopropene at 45 C to yield a dihydro-indene derivative 5. The addition of tetracyanoethene to benzocyclopropene giving dihydro-indene 6a is, however, believed to be preceded by electron transfer from benzocyclopropene to tetracyanoethene.Cyclopropa[b]naphthalene reacted similarly with tetracyanoethene to give the dihydroindene derivative 6b in 44% yield. 

Catalysts that yield highly syndiotactic polypropylene (86% racemic pentads) were also developed. One of them is /-propylene(ri -cyclopentadienyl-r fluorenyl)zirconium dichloride [291]. Initial disclosures of metallocene catalysts were followed by numerous publications in the literature that described similar materials for the polymerizations of either ethylene or propylene, or both, and for formation of various copolymers. Thus, for instance, Kaminsky et al. [292], reported preparaticm of a zirconium dichloride-type catalyst for copolymerization of cyclic olefins with ethylene. These cyclic olefins are cyclopentene, norbomene, and the hindered cyclopentadiene adducts of norbomene [292]. The catalytic system consists of a bridged indene derivative that is combined with methylaluminoxane ... 

Takahashi T, Kuzuba Y, Kong E, Nakajima K, Xi Z (2005) Formation of indene derivatives from bis(cyclopentadienyl)titanacyclopentadienes with alkyl group migratitm via carhon-carbon bond cleavage. J Am Chem Soc 127 17188... 

In further study of the reaction above, the formation of unusual indene derivatives 80 was found from bis(cyclopentadienyl)titanacyclopentadienes 76 via intermediate 79. Carbon-carbon bond cleavage of a Cp ligand occurred in the formation of complex 79, which was confirmed by C-enriched experiment. The alkyl group on the bridgehead of 79 transferred to give 80 by oxidation of the titanium metal center, as shown in Scheme 11.31 [32]. 

Recently, Wang et al. reported anovel palladium-catalyzed sequential Sonogashira/ carbopalladative cyclization/Suzuki reactions involving multiple carbon-carbon bond formation using protected homopropargyl alcohol 155 under mild conditions [59] (Scheme 6.40). Various indene derivatives 156 could be constructed efficiently with good yields in this transformation. Moreover, this reaction has a wide tolerance of various substituents in the substrates. 

A similar sequence of reactions on l,2-dihydroindeno[l,2-tautomeric mixture of the oxo 11a and hydroxy 12a forms.57 Prolonged treatment of the tetrahydro compound 10 with NBS in refluxing dibro-momethane results in bromination of the indene ring and formation of the 10-bromo derivative... 

Chemoselectivity plays an important role in the benzannulation reaction as five-membered rings such as indene or furan derivatives are potential side products. The branching point is again the rf-vinylcarbene complex D intermediate which maybe formed either as a (Z)- or an ( )-metallatriene the (E)-configuration is required for the cyclisation with the terminal double bond. (Z)-Metallatriene D, however, leads to the formation of furan derivatives H (Scheme 8). Studies on the formation of (E)- and (Z)-isomers discussing stereoelectronic effects have been undertaken by Wulff [17]. 

Thermolysis of 44 produced products derived from the Myers-Saito cyclization reaction. However, when 43 having a trimethylsilyl substituent at the acetylenic terminus was subjected to heating in the presence of 1,4-CHD at 70 °C for 3 h, the 1H-cyclobut[a]indene 46 was produced. A reaction mechanism involving an initial Schmittel cyclization to generate the benzofulvene biradical 45 followed by an intramolecular radical-radical coupling was proposed to account for the formation of the formal [2 + 2]-cycloaddition product 46. 

Similar surface-supported amides have been derived from the Sm" amide Sm N-(SiHMe)2 2(thf)x by grafting on MCM-41, MCM-48 or AS-200 further elaboration led to the formation of the corresponding Sm-fluorenone ketyl, which was shown to contain surface-confined ketyl radicals.Treatment of Sm N(SiHMe2)2 (thf)x MCM-41 with MeOH, AlHBu 2 or Si(H)Me2-substituted indene gave surface-supported catalysts for methyl methacrylate polymerisation. 

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. 

Should we wish to allow for related multi-ring species (> three rings), there are also enthalpy of formation data for carbazole (XLIX), dibenzofuran (L) and dibenzothi-ophene (LI), some benzo and dibenzotetraazapentalenes (also called benzoannelated triazolotriazoles) (e.g., LH, LIII, both drawn without formal charges) [81] and their nitro derivatives [82], for 4-methyl-4//-a/a- (LIV) and 4-oxa-indene (LV) [83] (also called /V-methyl-azalene or 1-pyrindene, and oxalene, respectively), or more properly the 2,3 5,6-dibenzo derivatives thereof, and for 1,2,4,5-benzenetetracarboxylic dianhydride (LVI) [84], However, in the name of brevity we have decided not to discuss these benzoannelated species in this chapter. Instead, these await future analysis. 

Block copolymerization between monomers of similar reactivities such as isobutene and various styrenes (styrene, p-chloro-, p-methyl-, and p-f-butylstyrenes, and indene) [284-288], as well as arMeSt and 2-chloroethyl vinyl ether [226], involves fewer limitations and is more successful. A detailed description of the copolymerization of ar-methylstyrene with 2-chloroethylvilnyl ether has been reported [226]. Because the reactivities of both monomers are similar, AB and BA block copolymers were prepared. However, the enhanced formation of indan derivatives was observed when vinyl ether was used as the first block. 

The relatively strong Bronsted acidity of cyclopentadienes, indenes, and fluorenes, permits the formation of alkali metal compounds of the conjugate bases of these organic molecules by direct reaction with the metal. The effect of substitnents on the rate of formation of 9-R-fluorenylhthium componnds in THE solution and on the degree of ion pairing in solutions of these species has been determined. Potassinm derivatives are commonly prepared by the reaction of the cyclopentadiene with potassium bis(trimethylsilyl)amide. Eluorenyl and indenyl compounds with the heavier alkah metals, Rb and Cs, are also prepared by reaction with the metal bis(trimethylsilyl)amide. The cyclopentadienyl ring in alkali metal compounds can also be coordinated to other metals. ... 

Based on the benzyl derivative (26), the first stable carborane-containing simple enol (27) was synthesized2 (Scheme 8). The acid chloride (28) readily enters into a Friedel-Crafts reaction with mesitylene to give ketone (29). Under the action of BuLi on a benzene-ether solution of ketone (29) enolate (30) is formed. Treatment of the latter with diluted HC1 solution results in enol (27). Starting from the benzyl derivative (31), carboranyl-substituted indene (32) was synthesized by intramolecular cyclization with a formation of ketone (33), whose reduction (34) followed by dehydration results in (32) (Scheme 9). 

Decomposition of (3), which might be formed from (1) or (2), can result in the formation of styrene or may lead to chain end unsaturation and neighboring ring protonation. Hydride abstraction by (3) would result in a saturated chain end. The lack of significant styrene production from any of the PS-catalyst samples suggests that P-scission of (3) to form styrene is not a dominant decomposition pathway at low temperatures. Chain end unsaturation derived from (3) may result in formation of indenes, which were detected in substantial amounts only when HZSM-5 catalyst was present. The restricted volume... 

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