Indenes rearrangement

The cyclopropene — indene rearrangement is a well known reaction which can be affected by acid87), heat 88,65d) or irradiation 20). The first transition metal catalyzed isomerization 89) has been published in 1968 (Eq. 30). 

Interest in this reaction was revived when the relevance of a carbene mechanism was realized, particularly following the demonstration (cf. SectionI,B) of a similar ring expansion of indene to 2-chloro-naphthalene by dichlorocarbene via the cyclopropane adduct. Indeed, at this time Nakazaki suggested that these reactions occurred by the addition of dichlorocarbene to the indolyl anion and subsequent rearrangement to the indolenine and, with loss of chloride ion, to the quinoline [Eq. (12)]. The preference of dichlorocarbene for... 

The cooxidation of thiophenol with indene by air in hydrocarbon solvents provides l-hydroperoxy-2-phenylthioindane 84 in 77% yield. Subsequent rearrangement afforded a mixture of trans and cis 2-phenylsulphinyl-l-indanols 85148 149 (equation 47). 

Positive photoresists, by contrast, are based on water-soluble novolak resins with naphthalene diazoquinone sulfonate (NDS) as the photosensi-tiser. On photolysis the NDS causes a rearrangement in the polymer to yield nitrogen gas plus an indene carboxylic acid. This latter functional group considerably increases the solubility of the polymer, hence solubilising those areas of the polymer that had been exposed to light. 

The PTAD adduct (123) from the 3aH-indene (91) rearranges and fragments on pyrolysis. The heterocyclic product is 2-methoxy-5-methylquin-oline. This novel fragmentation reaction is under further investigation.209... 

In both cyclic and acyclic dienes which can achieve the necessary geometry the [1, 5] shift is commonly observed because the activation energy is lowest for the transition states involving minimal distortion. This is particularly so in cyclopentadienes and indenes. The preference for [1, 5] over [1, 3] shifts is demonstrated by thermal rearrangement of 1-duterioindene. At 200°C, deuterium became scrambled over all three non-benzenoid carbons. 

As mentioned above, persistent carbocation 9 underwent rearrangement into cation 10 which rearranged further into cation 11. To reveal general relations/factors governing cationic rearrangements in benzopentalene derivatives, the behavior of 5,5,10,10-tetramethyl-5,10-dihydroindeno[2,l-fl]indene (12) in superacids was studied (52). It had been expected that hydrocarbon 12 would transform into the long-lived 5,5,10,10-tetramethyl-4b,5,9b,10-tetrahydroindeno[2,l-a]inden-4b-yl cation (13). However, H and 13C NMR data showed that hydrocarbon 12 transformed firstly into isomeric ion 14 which transformed further into cation 15 (Scheme 11). 

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. 

It was shown74 that the folded conformation of bicyclic substrates is a prerequisite for isomerizations such as 177 - 178. Thus, vyw-9-vinyl triene 183, being in the open conformation, undergoes an unusual Cope rearrangement to give the intermediate 184 which starts a cascade of thermal isomerizations at 60-65 °C (equation 57) whereas the awft -9-vinyl epimer 185 rearranges into the indene derivative 186 at 110°C in benzene solution (equation 58)74. 

Arylindenes undergo sigmatropic 1,5-shifts, induced oxidatively [267], thermally [268], photochemically [269], and re-ductively [270]. The reductive rearrangement of 1,1,3-triphenylindene, yielding the dianion of l,2,3-triphenyl-2H-indene, has been the subject of voltammetric investigations in DMF-TBAP [271]. The reaction follows an EEC or EDisp C pathway. 

Results of a theoretical study of 1,3-prototropic rearrangement of 1-methylindene, catalysed by ammonia and MesN in water and in cyclohexane, have confirmed earlier predictions that the proton moves freely over the indene ring once it has been abstracted by the base. The relative rates of deprotonation, ion-pair collapse and ion-pair rearrangement have been estimated and discussed in each case. 

These cycloadditions with o-quinodimethanes provide a broad variety of useful fullerene functionalizations, since o-quinodimethanes can be prepared using several routes and the resulting cycloadducts are thermally stable [42], There exist several alternatives to the iodide-induced bromine 1,4-elimination of 1,2-bis (bromomethyl)-benzenes [44-47]. o-Quinodimethanes have been prepared by thermolysis of 3-isochromanone (42) [43], benzocyclobutenes (43) [48-50], isobenzothiophene 2,2-dioxides (44) [42] and sultines [51,52] or by photolysis of o-alkylphenones such as 45 [53-55] and could be added to Cjq in good yields (Scheme 4.7). Indene, thermally rearranged to isoindene, also adds to Cjq in similar fashion to quinodimethanes [56]. 

At the present time, most of the positive photoresists used in the manufacture of microcircuits consist of a low molecular weight phenolic resin and a photoactive dissolution inhibitor. This composite system is not readily soluble in aqueous base but becomes so upon irradiation with ultraviolet light. When this resist is exposed, the dissolution inhibitor, a diazoketone, undergoes a Wolff rearrangement followed by reaction with ambient water to produce a substituted indene carboxylic acid. This photoinduced transformation of the photoactive compound from a hydrophobic molecule to a hydrophillic carboxylic acid allows the resin to be rapidly dissolved by the developer. (L2,3)... 

Reaction of atomic carbon with alkenes generally involves both DBA and vinyl C—H insertion. An interesting example is the reaction of C atoms with styrene in which the major products are phenylallene (21) and indene (22). The synthesis of a number of specifically deuterated styrenes and the measurement of the deuterium isotope effects on the 21/22 ratio led to the conclusion that 21 was formed by DBA followed by ring expansion and by C—H(D) insertion into and followed by rearrangement of the resultant frawi-vinylcarbene (23). The indene was formed by C—H(D) insertion into Xb followed by cyclization of the resultant cw-vinylcarbene (24) (Eq. 18). An examination of the product ratios and their label distributions when atoms are used leads to the conclusion that the ratio of C=C addition to C—H insertion is 0.72 1 in this case. 

Co-oxidation of indene and thiophenol takes place readily if the reactants in benzene solution are shaken with oxygen at temperatures in the range 20° to 40°C. (7). The major primary product has been shown to be frans-2-phenylmercapto-1 -indanyl hydroperoxide, I, which rearranges spontaneously to the two racemes of frans-2-phenylsulfinyl-l-indanol, II (8), and a tentative reaction scheme involving a three-step radical chain based on the suggestion of Kharasch, Nudenberg, and Mantell (11) was proposed for the formation of I. These three products accounted for 86% of the oxygen absorbed. 

Peroxide in solution is necessary to produce fast co-oxidation. When isooctane was used as solvent instead of benzene, a slow and linear oxygen uptake was observed (0.5 mole per mole of indene in 100 hours at 20°C.). This behavior was the result of low solubility in the paraffin of the hydroperoxide, I, which precipitated out and rapidly rearranged to inactive sulfoxides. 

Similarly, indenes undergo dye-sensitized photooxygenation at — 78°C in acetone to yield the usual oxygenated products, namely 2,3 7,9-diepoxy-6,9-peroxy-A4,5-hexahydroindenes (93). These compounds also undergo thermal rearrangement to form indene tetraepoxides (benzene oxides) (94) and are converted to 2,3 4,9 7,8-triepoxy-A5-6-hexahydroindenes (95) on treatment with trimethyl phosphite.49... 

The pH-rate profiles of the enol of l-indene-3-carboxylic acid and of its ketene precursor, formed from either l-diazo-2( 1 //jnaphthalenone or 2-diazo-l(2//)naphthalenone by photochemical deazotization and Wolff rearrangement, are shown in Fig. 5.36 The first and second acidity constants of the diol, p = 1.9 and p aE = 8.3, are evident from the downward curvature of log (k /s-1) at these pH values. The photo-Wolff rearrangement of diazonaphthoquinones is the active principle of Novolak photoresists. 

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