Diiodobenzene derivatives

Figure 35. Silver-mediated C X bond formation and preparation of diiodobenzene derivative.

PPVs are accessible by polycondensation methods based on transition metal-catalyzed cross-coupling processes. Several individual reactions are known. For example, using palladium catalysts, divinylbenzene yields with diiodobenzene derivates directly from PPV derivates. Another reaction, the Suzuki coupling, uses 1,4-aryldiboron acids and 1,2-dibromo-ethene with palladium catalysts to arrive at PPV. 

The first two precursors in this category to be discovered (see Table 5), 112 and 113, contain the relatively weak C-I and C-Hg bonds which undergo either photolysis or thermolysis to yield benzyne (1). The latter process is noteworthy as one of the first generations of this intermediate in the gas phase. Similar o-iodoorganometallic intermediates may be involved in the formation of arynes from o-diiodobenzene derivatives in the presence of zinc or copper. Both direct thermolysis and photolysis of 114 also lead to arynes, presumably via a stepwise mechanism involving o-iodophenyl radicals (47). The extent to which the latter go on to arynes depends not only on the nature of the aryl residue but, as mentioned in Section ILl.C, on the source of the radical center. Pyrolysis of dibromo (115), iodonitro (116), nitrobromo (117), and dinitro (118) aromatic compounds in a mass spectrometer also produces the corresponding arynes and didehydro compounds. 

More recently, hetero-capsules were reported by Kobayashi by combining the aforementioned fefra-acids with cavitand such as 26 [76]. Guests that bound included 1,4-diiodobenzene derivatives, which were shown to form C-H—X hydrogen bonds with the host. The orientational preferences in bound guests have been... 

An application of this reaction to aromatic ring extension is noteworthy. As shown in Eq. 2.43, zirconacydopentadienes couple with diiodobenzene (63) to afford naphthalenes 64. When tetraiodobenzene (65) is used, octasubstituted anthracene derivatives 66 are obtained [7c],... 

The photochemistry of borazine delineated in detail in these pages stands in sharp contrast to that of benzene. The present data on borazine photochemistry shows that similarities between the two compounds are minimal. This is due in large part to the polar nature of the BN bond in borazine relative to the non-polar CC bond in benzene. Irradiation of benzene in the gas phase produces valence isomerization to fulvene and l,3-hexadien-5-ynes Fluorescence and phosphorescence have been observed from benzene In contrast, fluorescence or phosphorescence has not been found from borazine, despite numerous attempts to observe it. Product formation results from a borazine intermediate (produced photochemically) which reacts with another borazine molecule to form borazanaphthalene and a polymer. While benzene shows polymer formation, the benzyne intermediate is not known to be formed from photolysis of benzene, but rather from photolysis of substituted derivatives such as l,2-diiodobenzene ... 

Reaction of iodosylbenzene with triflic anhydride gives an isolable, hygroscopic p-compound, sometimes called Zefirov s reagent upon longer reaction time (12 h), this isomerizes to a derivative of p-diiodobenzene which is also an iodonium salt (Scheme 11). The same compound was obtained directly from iodosylbenzene and triflic acid [47]. 

The domino Suzuki coupling-Heck reaction sequence involving dihydroaromatic alkenyl-substituted boronic esters (186) with diiodobenzene, bromoiodobenzene, or iodoaniline derivatives yields substituted phenanthrene (187) and phenanthridene derivatives regiospecifically (Scheme 52).218... 

The reaction of o-diiodobenzene with Ni(CO)4 gives a black compound of composition [NiC7H4I20]2 which is thought to be a benzyne derivative... 

A key reaction in the synthesis of the TIA alcohol 18 was the Suarez fragmentation (33) of the 2,3-O-isopropylidene-D-lyxose derivative 23 (34). Treatment of 23 with diiodobenzene diacetate (DIB) provided the 1,2-0-isopropylidene acetate 24 in 88% yield. Acetal exchange was effected by treatment of 24 with thiophenol and BF3.Et20 at -78 °C. Mild base hydrolysis of the product provided 18 in 90% yield from 24, and in 65% overall yield over the four one-pot operations for commercially available D-lyxose 22 (Scheme 3). 

The reaction of sodium enolates of -butyl acetate, A-acetylmorpholine and derivatives with iodoarenes catalyzed by Fe+2 salts in liquid ammonia gives good yields of substitution products. Bromoarenes react more sluggishly and chloroarenes almost do not react173, p-Diiodobenzene and p-chloroiodobenzene reacted with A-acetylmorpholine enolate and Fe+2 ions to give the disubstitution product in 55% and 51% yields, respectively173. 

The first reported thermotropic and lyotropic liquid-crystalline poly(aryleneethynylene)s were not parent PPEs, but organometallic derivatives 65 made by the Pd-catalyzed condensation of Vollhardt s diethynyl 64 with diiodobenzenes 46 [45]. The polymers were isolated in good to excellent yields as amorphous tan or red powders with moderate Pn values of... 

Biphenyls (entry 1) [84] or styrene derivatives (entries 2-4) [85], p-terphenyls (entry 5) [86], and m-terphenyls (entries 6-9) [87, 88] are synthesized from 2-bro-mo-1-iodobenzene, 2,5-dibromo-l,4-diiodobenzene, and 2,6-dibromo- or 2,6-di-chloro-1-iodobenzene, respectively, in moderate to good yields. 

Reactions of Miscellaneous Haloketones and Acid Chlorides. - The reactivity of anions such as (91) with 1,2-dihalobenzene (a. 1,2-diiodo, b.l-chloro-2-iodo and c. l-bromo-2-iodo) derivatives has been studied. The irradiations are brought about in DMSO as solvent. The reaction affords (92) as the principal product in variable yields (71 % from b, 86% from c and 50% from a), depending on which of the arene derivatives is used. The other product (93,17%) is formed only from reaction with o-diiodobenzene. The irradiation of the acid fluoride CF3CF2C(0)F has been described as an efficient route for the production of the radical, CF3CF2. This radical can recombine with CFO to afford the starting... 

Dihaloalkane and arene derivatives have proved to be a rich source of crystal engineering because of the robustness of supramolecular synthons such as X - I-C=C. The interaction energy of the N - I-C bonds in the 1 1 complex of 4,4 -bipyridyl and 1,4-diiodobenzene is 13.2kJmor with the N -1 distance being 3.03 A. The analogous complex with 1,4-diiodotetrafluorobenzene has an interaction energy of... 

The 9-membered cyclic ethers 116 have been prepared via oxy-Cope rearrangement of 115, ultimately derived from D-glucose. The 10-membered bis-ether 118 was prepared via Bergman cyclization of the bis-acetylene 117 (R=2,3,4,6-tetra-0-benzyl-p-D-glucosyl). Solution conformational analysis was reported from NMR experiments. Dialkyne 117 was prepared by Pd-catalysed coupling of the P-D-glucosyl-l-alkyne and 1,2-diiodobenzene, and a mechanism was proposed for... 

Jayakannan, M., J.L.J.V. Dongen, and R.A.J. Janssen. 2001. Mechanistic aspects of the Suzuki polycondensation of thiophenebisboronic derivatives and diiodobenzenes analyzed by MALDI-TOF mass spectrometry. Macromolecules 34 (16) 5386-5393. 

More recently, 13,14-dimethyldibenzo[6j][4,7]phenanthroline (55) was synthesized by the copper-catalyzed condensation reactions between 1,4-diiodobenzene (52) and 2-aminoacetophenone (53) to give 54 followed by sulfuric acid-promoted cyclization reactions (Scheme 10) [56]. Alternatively, 55 was also prepared by a one-pot procedure involving the ZnCl2-catalyzed reactions between AA -diphenyl-p-phenylenediamine (56) and acetic acid (Scheme 11) [57, 58]. The enantiomers of 55 were separated by a chiral HPLC column and were found to undergo rapid racemization at room temperature. A slower rate of racemization was observed for the 13,14-diethyl derivative 57. The X-ray structure of 57 confirmed the twisted aromatic framework. 

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