Лако-красочные материалы — производство

In analogy to other aromatic systems, nucleophilic aromatic substitution can also take place, depending on the substituents on the aromatic ring. For instance, 4,4′-dibromophenyl DPP 24 can react with amines at high temperatures in polar solvents to give 4,4′-diaminosubstituted DPP 26 as illustrated in Scheme 11.9 [32].

Scheme 11.8

11.4.3

W-Alkylation

The alkylation of the heterocyclic DPP moiety by alkyl halides or alkyl sulfonates yielded predominantly N-alkylated products, as exemplified by the N-methylation ofdiphenyl-DPP 2 (Scheme 11.10) [11, 16].

As a direct consequence of N-alkylation excluding the possibility of intermolec­ular hydrogen bond formation in the solid state, the solubilities of DPPs were drastically raised upon N-substitution (e. g., solubility in DMF at 25 °C: 100 mg/l for 2, whereas 3300 mg/l for 27). Most of the N-substituted DPP derivatives fluor­esced strongly, and with appropriately substituted derivatives Stokes’ shifts of up to 70 nm at fluorescence quantum yields of up to 95% have been reported (see Sec­tion 11.3.2).

11.4.4