ABSTRACT
The purpose of our research was to prove that the simple chemistry of pyridazinones could be built within the framework of polymer-supported synthesis, especially using our multidetachable linker. This was a new research direction, differing in many points from the similar currently popular synthesis techniques using polymer-supported reagents with substrates weakly bound to the polymer. Many new principles had to be elaborated and used for our research. These principles provide new directions for polymer-supported synthesis of nonbiopolymers. Our research could be characterized by the following points of view:
Examples were provided for synthetic transformations of pyridazinones, using two kinds of polymer-supported linkers.
The multidetachable linker was reusable many times; thus, it was not only accessible for anyone (easily prepared from polystyrene) but also economical.
Ring synthesis of the pyridazinone on the polymer support was avoided since it would have mainly led to cross-linked side products.
A stable attachment (within a pH range of 2–12 and up to temperature 170°C) was established for the N2-alkylated polymer-supported substrate.
78Further (nucleophilic) substitutions were carried out on polymer-supp orted substrates while the substrate still remained attached to the polymer.
Quantitative infrared spectroscopy was used for controlling each step.
Checking and evaluation of the courses of reactions were mainly on the basis of the area determination of the carbonyl band (ranging from 1740 to 1590 cm−1) of the infrared difference spectra (IDS) of the standardized spectra; the IDS were made by adjusting zero absorbance to an appropriate reference band (e.g., to the γC-H deformation vibration at 818 cm−1 or to the νC–C stretching vibration at 1034 cm−1), adjusting equal transmittances for the reference bands of the spectra to be compared.
Calculations on relative concentrations of the reagents (Charts 3.4–3.16, Chapter 3) were made by using dynamic swelling values, which were obtained during separate swelling experiments (Charts 3.1–3.3, Chapter 3) in various solvents.
Cleavage experiments were successfully carried out in the presence of acids (trifluoroacetic acid) or Lewis acids (BI3 or CuCl2), although occasional additional saturation of the pyridazinone ring took place.
Importance of the calculations of relative concentrations of the reagents to the substrate was thoroughly proven. There was a strong correlation between the relative concentration and the yield. Meanwhile, it was also proven that the overall weight or molar excess of the reagent was not important in itself.
