Synthesis procedure: second generation

The essence of the cascade synthesis is depicted in Scheme 2.1. Two procedures, alkylation and reduction, comprised the [a — b — a — b — ] sequence. Thus, treatment of a diamine with acrylonitrile afforded tetranitrile 3. Cobalt-mediated nitrile reduction gave tetraamine 4. Further amine alkylation provided the second generation octanitrile 5. The nonskid-chain-like [2] synthesis is shown in Scheme 2.2. Construction of polycyclic 6 was accomplished by repetitive alkylation, reduction, acylation, and reduction (a — b c— d—>a- b— ...) sequences. Again, repetitive and multiple reaction sequences were employed for the generation of new molecular assemblies. Most notable about these syntheses is that for the first time, generational molecules were prepared and characterized at each stage of the construction process. 

For the synthesis of the second generation ATH catalysts (see Figure 3 for the general structure), the bis(acetonitrile) complexes were dissolved in acetone and placed under CO atmosphere in the presence of KBr to give, after salt metathesis, complexes 64-72 (Scheme 13). " Alternatively, one acetonitrile can be replaced with CO by following the same procedure in the absence of KBr to obtain complex 73, which was tested for ATH with a variety of ketones. ... 

The second approach which generates poly(fi-aminoborazines) is based on the reaction of 5-chloroborazine derivatives with linking reagents such as silazanes in an one-step synthesis procedure. The earliest successful efforts to prepare poly[5-aminoborazine] according to this one-step synthesis procedure are those made by Paine et al. [38] They have synthesized a large variety of polymers by reaction of 5-chloroborazine derivatives with disilazanes. 

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