Synthesis of a New Class of Polyphenylated Phthalocyanines and Metallophthalocyanines
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Mat. Res. Soc. Symp. Proc. Vol. 488 ©1998 Materials Research Society
EXPERIMENTAL Typical Diels -Alder Cycloaddition Reaction to form 3 c Into a 50 mL drying ampul (ChemGlass) was added 2.00 g (8.81 mmoles) of 1 and 4.65 g (8.81 mmoles) of 2c along with 3 drops of cyclohexylbenzene. The ampul was sealed under vacuum after flushing with dry nitrogen gas. The tube was placed into a 215'C furnace for 6 hours. Upon cooling, the tube was broken and the mixture was deposited onto silica gel using dichloromethane. The solid was loaded onto a silica gel column and purified using flash chromatography and toluene/hexanes (1: 1) as the eluent. The fractions containing purified 3c, detected and analyzed by TLC, were collected and the solvent evaporated in vacuo. Recrystallization from methylcyclohexane gave the title compound as a white solid, melting point 205'C, yield 65% (4.17 g). Typical Cyclization Reaction of 3c to form 4b Into a 5 mL drying ampul (ChemGlass) was added 53.1 mg (0.073 mmoles) of 3c along with 4.9 mg of hydroquinone. The ampul was flushed with nitrogen and sealed under vacuum. The ampul was placed in a 225°C furnace for 48 hours. Upon cooling, the ampul was broken and the contents were deposited onto silica gel using dichloromethane. The solid was loaded onto a silica gel column and purified using flash chromatography with dichloromethane as eluent. The green fractions were collected and combined and the solvent removed in vacuo. This produced a waxy green solid, 11Img (0.004 mmoles), 20%. RESULTS AND DISCUSSION The syntheses of polyaromatic systems has been well investigated, and the use of the DielsAlder cycloaddition reaction between alkyne and cyclopentadieneone derivatives has been shown to be a powerful tool for building high molecular weight, fully aromatic compounds and polymers. 8 The current approach, outlined in Scheme I, consists of a Diels-Alder reaction between 4phenylethynylphthalonitrile, 1, and 2,3,4,5-tetraphenylcyclopentadiene-I-one (tetracyclone), 2a, to produce 4-(2,3,4,5,6-pentaphenyl)-phthalonitrile, 3a. This compound could then be forced to cyclictetramerize to produce the Pc of interest, 4a. This has proven to be possible and the methodology was extended to include alkoxy substituted derivatives such as 4b-f. Scheme I R
R
R
NN
UN
+
R
CN
2a-d
1 Compound a b C d
R H -OMe -OCAHo -OC 12H25
266
Yield % 80 68 65 70
3a-d
CN
4a-f Compound Compound 4a b c
d e f
Yield (%) Yield (%) 10
-OC 4H9
M -M 2H 2H
-OC 4 H9
Ni
20 37
-OC 4 H9
Pb
41
-OC12H25
2H Pb
30
R H
-O012H25
45
The synthesis of 1 begins with 4-nitrophthalonitrile as shown in Scheme II. Reduction9 followed by diazotization and iodide displacement gave 4-iodophthalonitrile, 5, which was catalytically coupled with phenylacetylene by Pd and Cu co-catalysts to prepare the Diels-Alder adduct 1.10 The cycloaddition reaction between 1 and 2 was selective in that the alkyne acted as the dienophile and not the nitrile. This is significant in that both possibilities have been reported at the reaction temperatu
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