Tertiary amine-catalyzed, ring-opening

Suzuki et al.[57 explored the Pd-catalyzed ring-opening of the monomer 5,5-dimethyl-6-ethenylperhydro-l,3-oxazin-2-one to give a hyperbranched polyamine. The polymerization was conducted at ambient temperature in THF and catalyzed with Pd2(dba)3-2 dppe, affording after the evolution of carbon dioxide, the desired hyperbranched polyamine. NMR spectroscopy confirmed the high yield conversion of the monomer. The degree of branching was ascertained (from NMR data) as the ratio of tertiary amine units to the total of secondary and tertiary moieties. 

Scheme 6.38 Ring-opening polymerization of L-lactide catalyzed by tertiary amine-functionalized thiourea rac-12.

Reaction with Nitrogen Nucleophiles. The acid-catalyzed reaction of primary, secondary, and tertiary amines with ethyleneimine yields asymmetrically substituted ethylenediamines (71). Steric effects dominate basicity in the relative reactivity of various amines in the ring-opening reaction with ethyleneimine (72). The use of carbon dioxide as catalyst in the aminoethylation of aliphatic amines, for which a patent application has been filed (73), has two advantages. First, the corrosive salts produced when mineral acids are used as catalysts (74,75) are no longer formed, and second, the reaction proceeds with good yields under atmospheric pressure. 

Polyformaldehyde. Polyformaldehyde or polyacetal is made by two different processes. Delrin is made from formaldehyde by anionic polymerization catalyzed by a tertiary amine. The homopolymer is end-capped with acetic anhydride. Celcon is made from trioxane cationic copolymerization using boron trifluoride catalyst and ethylene oxide (2-3%) as the comonomer. Boron trifluoride is a Lewis acid that associates with trioxane and opens up the six-membered ring. Ethylene oxide provides the end capping. Without an end cap, polyformaldehyde is thermally unstable and loses formaldehyde units. 

The most important applications of peroxyacetic acid are the epoxi-dation [250, 251, 252, 254, 257, 258] and anti hydroxylation of double bonds [241, 252, the Dakin reaction of aldehydes [259, the Baeyer-Villiger reaction of ketones [148, 254, 258, 260, 261, 262] the oxidation of primary amines to nitroso [iJi] or nitrocompounds [253], of tertiary amines to amine oxides [i58, 263], of sulfides to sulfoxides and sulfones [264, 265], and of iodo compounds to iodoso or iodoxy compounds [266, 267] the degradation of alkynes [268] and diketones [269, 270, 271] to carboxylic acids and the oxidative opening of aromatic rings to aromatic dicarboxylic acids [256, 272, 271, 272,273, 274]. Occasionally, peroxyacetic acid is used for the dehydrogenation [275] and oxidation of aromatic compounds to quinones [249], of alcohols to ketones [276], of aldehyde acetals to carboxylic acids [277], and of lactams to imides [225,255]. The last two reactions are carried out in the presence of manganese salts. The oxidation of alcohols to ketones is catalyzed by chromium trioxide, and the role of peroxyacetic acid is to reoxidize the trivalent chromium [276]. 

In the area of three-membered rings a similar mechanism is found for the sulfuric acid-catalyzed preparation of commercial hbPEI from ROP of aziridine (3-40) branching is guaranteed due to possible further reaction of secondary amines to tertiary amines after the first ring-opening step. The respective... 

Amines. Tertiary amines R3N are catalysts that open the epoxy ring and thus catalyze the polymerization reaction. They may be used with hydroxyl-containing molecules to catalyze homopolymeiization (Fig. 3.26), but more often they are used to catalyze copolymerization of epoxy resins with amine or acid curing agents. Several more specialized amines are also mentioned as catalysts (Fig. 3.27). 

PO also reacts with active hydroxyl hydrogen derived from the ring opening of other compounds such as EO and tetrahydrofuran thus, a copolymer polyol is obtained. Typically, polyols are obtained from base-catalyzed reactions with aqueous ammonia, sodium or potassium hydroxide, or lower alkyl tertiary amines such as trimethyl- and triethylamine. The reaction of PO with tetrahydrofuran is catalyzed by boron trifluoride etherate. The molecular weights of polyols prepared according to the reactions described earlier range from 200 to 7000. 

The uncatalyzed ECN-PN reaction is very slow compared to the catalyzed epoxyphenol reaction. The uncatalyzed equimolar epojq -phenoUc reaction was also found to be slu sh by Shechter. A cure carried out at 200 C required 12 hours to consume 90% of the epoxy. In addition, the catalyzed epoxy homopolymerization reaction (Rxns. 27 and 28) was found to be very slow by Shechter and by Narracot. It was actually necessary to add alcohol in order to trigger any reaction, and then reaction was observed between only epoxy and the alcohol. It was concluded that the zwitterion formed by the ring opening reaction between the tertiary amine and the epoxy (Rxn. 27) is unable to react with epoxy. This was beUeved to be due to the proximity of the zwitterion s positive and negative charges." ... 

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