Indenes, formation

Scheme 11 Phenol versus indene formation. (AffM co=metal-CO bond strength Arefers to substitution of CO for PR3)...

Table 6.2 Ruthenium catalyzed indene formation reaction. ...

In the case of 3-aryl-substituted 3//-pyrazoles [e.g. dimethyl 3,3-diphenyl-3//-pyrazole-4,5-dicarboxylate (7)] indene formation often competes with formation of the cycloprop-... 

Certain alkyne and carbene substitution patterns divert the reaction toward predominant indene formation. For example, ynamines and ynediamines both react with chromium arylalkoxycarbenes to give isolable vinyl carbenes, which proceed on to indenes thermally [21 a, b]. Chromium aryla/nmocarbenes also lead to good to excellent yields of indanones after hydrolysis of the enamine [Eq. (19)] [45]. In this latter case, the increased electron-donating... 

Manipulation of reaction conditions can dramatically and systematically alter the product distribution. For example, use of dimethylformamide (DMF) solvent leads to an 83 % yield of the indene from the reactants in Eq. (18) [45]. Similar effects have been particularly well documented for orr/to-substituted arylcarbenes, for which the empirical observation is that indene formation is greatest in relatively high-dilution, high-temperature reactions, in polar, coordinating solvents [Eq. (21)] [9]. 

Yamamoto et al. reported a PtBr2-catalyzed cyclization of l-ethynyl-2-(l-alkoxy-but-3-enyl)-benzenes 117, which furnished functionalized indenes 118 in good to allowable yields (Scheme 46) [124]. Notably, the allyl group substituted at benzylic position was indispensable for the success of this cyclization, without which the reaction did not work at all. This observation suggests that the coordination of olefin to platinum at a right position/geometry might be essential for the indene formation. 

The vitamin D3 metabolite la,25-dihydroxycholecalciferol is a lifesaving drug in treatment of defective bone formation due to renal failure. Retrosynthetic analysis (E.G. Baggjolint, 1982) revealed the obvious precursors shown below, a (2-cyclohexylideneethyl)diphenylphosphine oxide (A) and an octahydro-4f/-inden-4-one (B), to be connected in a Wittig-Homer reaction (cf. section 1.5). 

A significant modification in the stereochemistry is observed when the double bond is conjugated with a group that can stabilize a carbocation intermediate. Most of the specific cases involve an aryl substituent. Examples of alkenes that give primarily syn addition are Z- and -l-phenylpropene, Z- and - -<-butylstyrene, l-phenyl-4-/-butylcyclohex-ene, and indene. The mechanism proposed for these additions features an ion pair as the key intermediate. Because of the greater stability of the carbocations in these molecules, concerted attack by halide ion is not required for complete carbon-hydrogen bond formation. If the ion pair formed by alkene protonation collapses to product faster than reorientation takes place, the result will be syn addition, since the proton and halide ion are initially on the same side of the molecule. 

Quaternary salt formation by the l,5-diaza-3H-indene 103 is reported to take place only at N-5 to give 104. This information is... 

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... 

By analogy with the formation of3//-azepines by cycloaddition of 2//-azirines withcyclopenta-dienones, l,3-diphenyl-2//-inden-2-one (58) and its dibenzo analog 60 enter into [4 + 2] cycloadditions with 27/-azirines to give 3//-2-benzazepines 59 and phenanthro[9,10-e]azepincs 61, respectively.96... 

The epoxidation method developed by Noyori was subsequently applied to the direct formation of dicarboxylic acids from olefins [55], Cyclohexene was oxidized to adipic acid in 93% yield with the tungstate/ammonium bisulfate system and 4 equivalents of hydrogen peroxide. The selectivity problem associated with the Noyori method was circumvented to a certain degree by the improvements introduced by Jacobs and coworkers [56]. Additional amounts of (aminomethyl)phos-phonic acid and Na2W04 were introduced into the standard catalytic mixture, and the pH of the reaction media was adjusted to 4.2-5 with aqueous NaOH. These changes allowed for the formation of epoxides from ot-pinene, 1 -phenyl- 1-cyclohex-ene, and indene, with high levels of conversion and good selectivity (Scheme 6.3). 

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]. 

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]. 

The superior donor properties of amino groups over alkoxy substituents causes a higher electron density at the metal centre resulting in an increased M-CO bond strength in aminocarbene complexes. Therefore, the primary decarbo-nylation step requires harsher conditions moreover, the CO insertion generating the ketene intermediate cannot compete successfully with a direct electro-cyclisation of the alkyne insertion product, as shown in Scheme 9 for the formation of indenes. Due to that experience amino(aryl)carbene complexes are prone to undergo cyclopentannulation. If, however, the donor capacity of the aminocarbene ligand is reduced by N-acylation, benzannulation becomes feasible [22]. 

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). 

Oxidation, of Grignard reagents with peresters, 41, 91 43, 55 of 2-hydroxy-3-methylbenzoic acid to 2-hydroxyisophthalic acid by lead dioxide, 40, 48 of indene, 41, 53 44, 63 of indolepyruvic add, 44, 66 of methyl disulfide to methanesul finy 1 chloride by chlorine, 40, 62 of 2-exo-norbomyl formate by chromic add, 42, 79... 

The workhorse of the VLSI industry today is a composite novolac-diazonaphthoquinone photoresist that evolved from similar materials developed for the manufacture of photoplates used in the printing industry in the early 1900 s (23). The novolac matrix resin is a condensation polymer of a substituted phenol and formaldehyde that is rendered insoluble in aqueous base through addition of 10-20 wt% of a diazonaphthoquinone photoactive dissolution inhibitor (PAC). Upon irradiation, the PAC undergoes a Wolff rearrangement followed by hydrolysis to afford a base-soluble indene carboxylic acid. This reaction renders the exposed regions of the composite films soluble in aqueous base, and allows image formation. A schematic representation of the chemistry of this solution inhibition resist is shown in Figure 6. 

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. 

Intramolecular secondary aminostyrenes 95-97 were also studied100. iV-2,2-Trimethyl-3-phenyl-3-buten-l-amine 95 was irradiated to obtain the elimination product 98 (equation 29). Irradiation of Af-methyl-4-phenyM-penten-l-amine 96 results in a single product 99 in 80% yield by GC analysis (equation 30). Similarily, irradiation of iV-methyl-5-phenyl-5-hexen-l -amine 97 results in the formation of a single product 100 in 70% yield (equation 31). The photochemistry of the (aminopropyl) indene 101 is also similar (equation 32). 

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. 

Catalytic asymmetric methylation of 6,7-dichloro-5-methoxy-2-phenyl-l-indanone with methyl chloride in 50% sodium hydroxide/toluene using M-(p-trifluoro-methylbenzyDcinchoninium bromide as chiral phase transfer catalyst produces (S)-(+)-6,7-dichloro-5-methoxy-2-methyl-2--phenyl-l-indanone in 94% ee and 95% yield. Under similar conditions, via an asymmetric modification of the Robinson annulation enqploying 1,3-dichloro-2-butene (Wichterle reagent) as a methyl vinyl ketone surrogate, 6,7 dichloro-5-methoxy 2-propyl-l-indanone is alkylated to (S)-(+)-6,7-dichloro-2-(3-chloro-2-butenyl)-2,3 dihydroxy-5-methoxy-2-propyl-l-inden-l-one in 92% ee and 99% yield. Kinetic and mechanistic studies provide evidence for an intermediate dimeric catalyst species and subsequent formation of a tight ion pair between catalyst and substrate. 

The intermediate vinylketene complexes can undergo several other types or reaction, depending primarily on the substitution pattern, the metal and the solvent used (Figure 2.27). More than 15 different types of product have been obtained from the reaction of aryl(alkoxy)carbene chromium complexes with alkynes [333,334]. In addition to the formation of indenes [337], some arylcarbene complexes yield cyclobutenones [338], lactones, or furans [91] (e.g. Entry 4, Table 2.19) upon reaction with alkynes. Cyclobutenones can also be obtained by reaction of alkoxy(alkyl)carbene complexes with alkynes [339]. 

The observed ambient organic aerosol formation rates are also consistent with those estimated by extrapolation of smog-chamber kinetic data. Other heavy unsaturates, such as styrene and indene, are present in the atmosphere and may contribute, in part, to the formation of benzoic acid and homophthalic acid, respectively. Diesel exhaust and industrial emission are possible sources of such heavy unsaturates. Diolefins of C6+ are not present in gasolines and exhaust gases and have not been found in the atmosphere, and their possible role as precursors of the Cs-7 difiinctional acidic compounds is seriously challenged. Lower diolefins are emitted in automobile exhaust. Examination of vapor-pressure data indicates that the bulk of their expected photooxidation products remains in the gas phase, including most of the less volatile C3-4 dicarboxylic acids. 

Bromine-atom atomic resonance absorption spectrometry (ARAS) has been applied to measure the thermal decomposition rate constants of CF3Br in Kr over the temperature range 1222-1624 K. The results were found to be consistent with recently published theory. The formation of cyclopent[a]indene and acenaphthylene from alkyl esters of biphenyl-mono- and -di-carboxylic acids has been observed in flash vacuum pyrolyses at 1000-1100 °C. The kinetics and mechanisms of free-radical generation in the ternary system containing styrene epoxide, / -TsOH, and i-PrOH have been examined in both the presence and absence of O2. ... 

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