Indacene

The s-indacene (III) synthesized by Hafner s group and its 7-membered analogue (IX) are predicted to assume a skewed structure with a moderate double-bond fixation. As for (III), this conclusion supports the previous theoretical works and is in accordance with the experimental information. 

As shown in the two examples described here, formation of the benzene nucleus by trimerization of alkynes is usually catalyzed by a Co-complex. However, Und-heim and coworkers [276] have recently shown that a Ru "-complex can also be used. Reaction of the triyne 6/4-9, which was prepared from SchollkopPs bislactim ether 6/4-8 [277] with Grubbs I catalyst 6/3-13, led to 6/4-10 in an excellent yield of 90%. Hydrolysis of 6/4-10 gave the desired as-indacene-bridged bis(a-amino acid) derivative 6/4-11 (Scheme 6/4.3). 

BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) Dyes... 

Fluorophores containing 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene as a core skeleton are commonly designated as BODIPY fluorophores. Due to their useful photophysical properties including high fluorescence quantum yields, high molar absorption coefficient, narrow absorption and emission band width, and their high photostability [50], BODIPY dyes are proven to be extremely versatile and useful in many biological applications Fig. 11 [68]. 

Similarly, the five-membered sulfur analogue 4//,8//-2-oxa-6-thia-l,3,4,5,7,8-hexaaza-t-indacene 330 can be formed on treatment of 329 with sulfur monochloride at elevated temperatures in dimethylformamide (DMF) (Equation 88) <1999CHE499>. 

This approach has also been utilized by Moskovkina and Kaminskii where furazan-3,4-diamine 397 was reacted with the cr-chloroketone 398 to generate the dihydroindacene 399 in 15% yield along with the oxidized indacene 400 in 10% yield (Equation 107) <1999CHE882>. 

BODIPY is a short for 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene, the basic structure of this type of fluorophore (see Fig. 6.5). Derivatives of this dye have been created by modification of positions 1, 3, 5, 7, and 8, generating an array of fluorophores with very distinct excitation and emission properties [38]. Molecular Probes has synthesized a wide number of BODIPY dyes whose excitation... 

BODIPY fluorophores are a class of probes based on the fused, multi-ring structure, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (Figure 9.27) (Invitrogen) (U.S. patent 4,774,339). This fundamental molecule can be modified, particularly at its 1, 3, 5, 7, and 8 carbon positions, to produce new fluorophores with different characteristics. The modifications cause spectral shifts in its excitation and emission wavelengths, and can provide sites for chemical coupling to label biomolecules. 

BODIPY FL C3-SE is 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionic acid, succinimidyl ester (Invitrogen). The derivatization to the base BODIPY molecule... 

Br-BODIPY 493/503 8-Bromomethyl-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-3-indacene MW 341... 

The PE spectra of cyclobutadiene 281192, tetra-t-butylcyclobutadiene 282193, 1,3,5-tri-t-butylpentalene 283194 and aceheptylene 284195, all of which are subject to second-order bond localization, have been described in the literature. Further examples are 1,3,5,7-tetra-t-butyl-s-indacene 285 (which exhibits a first double band 1,2 at I 2 = 6.75 eV, followed by two bands at I = 8.50 eV and I = 9.30 eV) and the tetracyclic hydrocarbon 1,3,6,8-tetra-t-butylpentaleno[2,l-a]pentalene 286 (the first two bands of which are observed at 6.40 eV and 7.65 eV)196. 

Schardt, S. and Hafner, K., Synthesis of l,3,5,7-tetra-ferf-butyl-4,8-diphospha-s-indacene, Tetrahedron Lett., 37, 3829, 1996. 

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