Dihydroindeno fluorene

Reactions arising via photo-oxidation of diazo-compounds are thought to involve carbonyl oxide intermediates, and stilbene derivatives are formed via aryldiazomethane radical-cations on dicyanoanthracene-sensitized irradiation of aryldiazomethanes. " A 1,4-biradical is formed by stepwise cleavage on photolysis of l,12-bis(diazo)-l,12-dihydroindeno[2,3-a]fluorene. ... 

Access to the [1,2-6]IF core was also discovered through collapse of the dehydrobenzo[12]annulene scaffold. First described by Eglinton and coworkers in 1960 (Scheme 6), tetrayne 24 underwent a double transannular cyclization when reacted with elemental Na in liquid ammonia to provide octahydroindeno[l,2-(7] fluorene 25 as a mixture of two isomers in 69% yield [41]. Further treatment with 15% Pd/C aromatized the central ring to afford 6,12-dihydroindeno[l,2-/7] fluorene (26). 

The most common route to IF diones is still based on Deuschels original 1951 procedure [25]. In 2002, Wang and coworkers modified this synthesis, utilizing a Suzuki cross-coupling reaction to generate terphenyl 20, which was then oxidized and cyclized as before to yield 22 from 2,5-dibromo-p-xylene 58 in 85% yield over three steps (Scheme 13) [48]. Dione 22 could subsequently be reduced to form known 6,12-dihydroindeno[l,2-I>]fluorene (26). 

First synthesized by Deuschel in 1951 via dehalogenation of 23 (Scheme 27) [26], 6,12-dihydroindeno[l,2-h]fluorene (26) can be viewed as a planarized p-terphenyl derivative. As a result of the enforced geometry, there is greater cmijugation between the phenyl rings, which imparts more desirable emissive properties thus, this core unit has been utilized in a wide variety of molecular and polymeric systems — far too many to be reviewed here. Rather, selected, salient examples will be presented. 

Many synthetic routes are utilized to generate 6,12-functionalized dihydroindeno[l,2-h]fluorenes, typically from 22 or 26. One direct method is base-promoted alkylation of the methylene carbons of 26. For example, lithiation of 26 followed by treatment with 1-bromooctane gave tetrasubstituted 101 (Scheme 29) [80]. Subsequent bromination at the 2- and 8-positions with CuBr/ alumina furnished 102, which could then be polymerized to form polyindeno-fluorene 103 linked at the 2- and 8-positions rather than at the 6- and 12-positions as seen in Scherf s polyindenofluorene 85. Muellen and co-workers foxmd that 103 showed a bathochromic shift in fluorescence compared to polyfluorene (into the visible region) and it formed a liquid crystalline phase at high temperature, possibly making a suitable LED component. 

An alternative route to functionalized dihydroindeno[l,2-Z>]fluorenes begins from fluorenone and involves intramolecular Friedel-Crafts alkylation in the final step, leading to spiro-fused derivatives - a method championed by Rault-Berthelot,... 

A mixture of 5-methyl-ll,12-dioxo-ll,12-dihydroindeno[2,l-a]fluorene, Zn-powder, and SiOa heated several hrs. at 310° in a slow Hg-stream 5-methyl-ll,12-dihydroindeno[2,l-a]fluorene. Y 70.7%. F. e. s. L. Chardonnens and S. Bitsch, Helv. 55, 1345 (1972). 

Methyl-substituted arylboronic acids underwent cross-coupling/C—H activation cascade with various 1,2-dihalobenzenes, including l-chloro-2-halobenzenes in the presence of PdOAc)2/PCy3 as a catalyst and M2C03/rBuC02H (M = K, Cs) as a base [67], For example, 6,12-dihydroindeno[l,2- ]fluorene 194 was obtained in 73% yield from 191 and 192 (Scheme 22.44). 

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