Nickel Hemiporphyrazines as Bisdienes and Bisdienophiles: Synthesis and Characterization

Abstract

The bisdienophilic (hemiporphyrazinato)nickel complexes la-d bearing various alkoxy groups were synthesized from diiminoisoindoles 9a-d, diaminopyridines 10a, d, and nickel acetate. Reaction of la-d with a n excess of pentaene 3 delivered the macrocyclic bisdienes 2a-d. The hemiporphyrazines were characterized by 'H-and 13C-NMR spectroscopy. The NMR spectra of the 1,6,16,21-tetrabutoxy-substituted compounds l b and 2b are discussed with respect to the presence of synlanti isomers.Recently, we reported on the (hemiporphyrazinato)nickel-(11) complexes (HpNi) 1, 2['1 and the pentaene 3['] as building blocks for the synthesis of ladder oligomers and polymers, e.g. the conversion of equimolar amounts of 1 and 2 (with R' = C4H9, R2 = H) in a repetitive Diels-Alder reaction delivered the polymer 4. The compounds 1 and 2 can be classified as macrocyclic bisdienes and bisdienophiles. We now describe the synthesis of the nickel hemiporphyrazines 1 and 2 bearing various peripheral alkoxy groups. The 1,6: 16,21-tetrasubstituted HpNi as 1 are superior to the related 2,5 : 17,2O-tetrasubstituted compounds concerning their reactivity in Diels-Alder reactions"]. This fact may be due to steric reasons.The synthetic route started with tetrabromohydroquinone (5)r4], which was obtained from hydroquinone and bromine in acetic acid. Treatment of the disodium salt of 5 with alkyl halidesL51 [RX = CH31 (a); C4H9Br (b); C6H13Br (c)] led to the corresponding tetrabromohydroquinone bisalkyl ethers 6a-c. Compounds 6a-c were subsequently converted at -50°C with a 1.2 molar amount of nBuLi to the corresponding monoarynes, which in situ underwent with furan a Diels-Alder reaction[q with formation of 5,sdialkoxy-6,7-dibromo-1,4-dihydro-1,4-epoxynaphthalenes 7a-c. A Rosenmund-von Braun of 7a-c using CuCN in DMF afforded 6,7-dicyanonaphthalenes 8a-c. The reaction of 8a-c with NH3 in MeOH (catalyzed by CH30-, 7 days) delivered the corresponding diiminoisoindoles 9a-c. To synthesize the hemiporphyrazines la-d[*], the isoindoles 9a-c were stirred in n-butanol at 100°C with 2,6-diaminopyridine or 2,6-diamino-4-butoxypyridine, respectively. The subsequent addition of Ni(OAc), . 4 HzO at 100°C led to a strong evolution of ammonia. The metalation was finished after an additional heating at 120 "C for 2 hours. The products were purified by column chromatography (alumina and silica gel). The yields of the macrocycles la-d increase with increasing chain length of the peripheral alkoxy substituents.The excellent solubility of the HpNi la-d in solvents like chloroform, dichloromethane, or toluene allows their characterization by 'H-and "C-NMR spectroscopy. Figure 1 shows as an example the 'H-NMR spectrum of lb.Characteristic of the 'H-NMR spectra of hemiporphyrazines are the signals resulting from 9-H (triplet, 6 = 7.37) and 8-H (doublet, 6 = 6.47) of the pyridinc fragment. The resonances of 1-H and 2-H appear as singlets at 6 = 7.00 and 5.90, respectively. The HpNi la-d are present as a mixture of synlanti isomers due to the relative orientation of the oxy...

Hemiporphyrazines as Targets for the Preparation of Molecular Materials: Synthesis and Physical Properties

“…It can be carried out either with bis-dienophiles (“AA-monomers”) and bis-dienes (“BB-monomers”) or starting from a diendienophile (“AB-monomer”). Various substituted diepoxyhemi naphtho porphyrazines, e.g., 18 − 22 , have been prepared as AA-monomers for such a reaction (Figure ) . Again, the introduction of lipophilic side chains is necessary to achieve sufficient solubility of the bis-dienophiles.…”

“…The first strategy consisted of treating 18 with an excess of the tetraenes 23a , b . The occurring exo-selective Diels−Alder reactions led to the BB-monomers 24a , b as major products 27c).…”

“…AB-monomers such as 35 and 36 can be prepared by following the above-described routes if the relative amounts of 23 or 25 are chosen appropriately (0.4−1 equiv). 27b,

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Star‐Shaped Molecules Containing Polyalkynyl Groups with Metal Moieties on Benzene and Triphenylene Cores

“…Synthesis of 1,2,4,5‐Tetrabromo‐3,6‐dibutoxybenzene (C): Synthesis of C followed the same procedure as that used for the preparation of B . Their spectroscopic data are the same as that of literature 27…”

Synthetic approaches to asymmetric phthalocyanines and their analogues

“…167,168,[205][206][207][208] Such phthalocyanines easily form Diels-Alder reaction products when reacted as dienophiles under mild conditions with different dienes. When tetraphenylcyclodienone is used in reaction with asymmetric phthalocyanine 26a, thermal decomposition of the reaction product 40 in situ generates the furan-substituted phthalocyanine intermediates 40a, which could be used as dienes in further Diels-Alder reactions with bicyclic dienophiles to form ladder-type oligomers 41 incorporating phthalocyanine units (Scheme 16).…”