**3.2. Synthesis of branched poly(amines)**

**Figure 3.** ESI mass spectrum of *cis* and *trans* isomers of di(3,5,5‐ trimethylhexyl)cyclohexane‐1,2‐dicarboxylate.

of di(n‐ and isononyl)cyclohexane‐1,2‐dicarboxy‐

**Figure 4.** General mass fragmentation scheme of molecular ions [M]+

236 New Advances in Hydrogenation Processes - Fundamentals and Applications

lates.

Hyperbranched polymers can be prepared by various stepwise and repetitive chemical routes within which convergent and divergent methods are of the biggest practical meaning [24–26]. One of the easiest and the most effective way to synthesize the hyperbranched polyamines is cyanoethylation of primary amines followed by hydrogenation of resulting nitriles to generate primary amines. This process consists of an initial Michael's addition of a core amine to acrylonitrile, and then in the presence of Raney nickel hydrogenation to core amine, which can be further processed in a stepwise manner. Katriztky et al. [27] synthesized various nitriles with the addition of acetic acid as a catalyst with yields reaching 90% but then failed to obtain pure primary amines in hydrogenation process over Raney nickel catalyst with the addition of ammonia in methanol, preventing from formation of secondary amino functionality. Buhleier et al. [28] by means of NaBH4∙CoCl2 reduced nitrile in 24% yield. After 15 years, this process was modified by using diisobutylaluminium hydride in a mixed solvent system of THF and hexane [29]. Worner and Mülhaupt performed hydrogenation of nitriles over Raney nickel in the presence of sodium hydroxide as a cocatalyst, which led to a decrease in reaction yield (ca. 70%) due to the retro‐Michael reaction caused by the action of a strong base [30].

De Brabander‐van der Berg and Meijer reported successful hydrogenation over Raney cobalt catalyst in water under H2 pressure of 30–70 bar. Under these conditions no side products were obtained and 99.5% selectivity level per conversion was achieved [31].

The cross‐linking agents (N,N,N‐tri(3‐aminopropyl)amine and (N,N,N′,N′‐tetra(3‐amino‐ propyl)ethylenediamines were obtained in the catalytic hydrogenation process of appropri‐ ate poly(nitriles) in the presence of modified silica support Ni catalyst.

Preparation of N,N,N‐tricyanoethylamine (TCA) and N,N,N′,N′‐tetracyanoethyl‐1,2‐ethyle‐ nediamine (TCED) was performed by means of bimolecular Michael addition of acryloni‐ trile to ammonia and ethylenediamine, respectively. The exotermic reaction of poly(nitriles) intermediates TCA and TCED starts with an addition of excessive acrylonitrile to the appro‐ priate amine under ambient conditions.

The poly(nitriles) used for hydrogenation process were synthesized in the reaction of 30% water solution of ammonia or 1,2‐ethylenediamine containing 1,4‐dioxane and ionic liquid with an excessive amount of acrylonitrile. When the reaction was completed at 60°C, poly(ni‐ triles) were separated by means of a separatory funnel and dried over magnesium sulfate in order to remove any traces of water.

The synthesized poly(nitriles) are the substrates in the hydrogenation reaction to obtain the primary poly(amines). This reaction was carried out in the presence of the Ni catalyst in the high‐pressure autoclave giving the final product of the polyamines—(N,N,N‐tri(3‐amino‐ propyl)amine) (TAA) or (N,N,N′,N′‐tetra(3‐aminopropyl)‐ethylenediamine)) (TAED) with 82.0% and 88.0% yields, respectively.

Poly(nitriles) used for hydrogenation reaction were obtained in a cyanoethylation process, as shown in **Figure 5** without purification procedures.

**Figure 5.** Cyanoethylation of ammonia and 1,2 ethylenediamine to N,N,N tricyanoethylamine (TCA) — 3 and N,N,N',N' tetracyanoethylo 1,2 ethylenediamine (TCED) 4 followed by their hydrogenation reaction gives (N,N,N tri(3 aminopropyl)amine) (TAA) — 5 and (N,N,N',N' tetra(3 aminopropyl)ethylenediamine)) (TAED) — 6, respectively.

The hydrogenation reactions were carried out at 135°C, under 10 bars for 6 h. In the case of TAA synthesis, yield of this reaction reached 85.7%, while for TAED exceeded 82%.

In case of hydrogenation of TCA for 0.14 mol of nitrile, 0.42 mol of H2 is needed for total conversion of nitrile groups into primary amino groups. It was determined that to achieve full

conversion of poly(nitriles) to the poly(amines) seven cycles of refilling hydrogen were necessary, which equaled to 0.42 mol of H2. Exactly the same procedure was applied for hydrogenation of TCED, but full nitrile reduction was achieved after 12 cycles of hydrogen refill. In this case 0.72 mol of hydrogen was needed for the completion of the hydrogenation process (**Figure 6**).

**Figure 6.** Hydrogenolysis of the TCA to N,N‐diaminepropylamine and n‐propylamine.
