N-phthalimides

An alternative order of introducing acylating reagents onto the bis[3-amino-4-(p-aminophenoxy)]-benzophenone, that is, the addition of first bis(phthalic anhydride) and then phthalic anhydride to the tetramine, yields polyimides containing predominantly N-phthalimide o-substituents (Scheme 3.7). These polyimides are characterised by higher viscosities and softening temperatures (Table 3.8) but poorer solubilities as compared to those polymerised according to Scheme 3.6. 

All the polyimides show solubility in NMP, w-cresol and BL. Moreover, all polyimides, except for that based on 3,3, 4,4 -tetracarboxydiphenyl ether, are soluble in THF, chloroform and CH, while polyimides derived from dianhydride 6F also show solubility in acetone. This fact is explained by the presence of N-phthalimide and methyl substituents, /-phenylene fragments and hexafluoroisopropylidene groups, as well as by the mild conditions of the synthesis. 

All polyimides obtained dissolved readily in NMP, DMF and TCE/phenol (3 1). The good solubility of these polyimides is due to the presence of methyl and N-phthalimide side groups in their macromolecules, the presence of different isomers and mild catalytic imidisation conditions. 

N-Phthalimide-linked peptides that contain C-terminal a-amidotrimethylsilyl groups undergo macrocyclization reactions via sequential single-electron transfer processes [11, 12]. Thus, electron transfer from the neighboring amide to the excited phthalimide chromophore leads to an amide radical cation. Hole migration to the ot-amidotrimethylsilane center is followed by desilylation to form an 1, co-biradical intermediate, which finally cydizes to the macrocydic peptide (Scheme 9.9). 

C-labelled glycines have been prepared " from the corresponding bromoacetic acids , used in the synthesis of the 2, 3, 5 -tri-C)-benzoyl[4- C]uridine and regiospecific introduction of isotopic carbon or nitrogen into one or more positions of the pyrimidine ring . [ N]glydne has been prepared from potassium [ N]phthalimide . 

Scheme 10. Chemoenzymatic synthesis of sialylated lactosamine with N-phthalimide as N protecting group.

Scheme 11. Ubiquitous ring opening in water of N-phthalimide protecting groups.

Tri-Ac, "N-phthalimide 3,4,6-Tri-O-acetyl-2-deoxy-2-phthalimido-p-D-gluco-pyranosyl trichloracetimidate C22H21CI3N2O10 579.773... 

Bis [4-(3-Ethynylphenyl-N-phthalimide) ] hexafluoropropane (7) The bisimide was prepared from the reaction of 2,2-bis(3, 4 -dicarboxy-phenyl)hexafluoropropane dianhydride with two moles of 3-aminophenyl-acetylene in glacial acetic acid. Purification by chromatographing on silica gel provided the material with a mp 185-186 C, reported mp 180-186 C. 

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