Sterically hindered amine derivative

In another approach, a polymer-bound TEMPO-species, referred to as PIPO (polyamine immobilized piperidinyl oxyl), was derived by oxidation of commercially available Chimasorb 944, an oligomeric sterically hindered amine. Together with bleach as co-oxidant PIPO (12) afforded aldehydes and ketones in short reaction times and with yields from 80 to > 99% (Scheme 4.6) [70]. 

J. Luston u. F. Vass, Makromol. Chem., Macromol. Symp. 27, 231-237 (1989) . .Functional Derivatives of Sterically Hindered Amines. 1. Glycidyl Compounds". 

Reaction of aLkyknagnesium reagents with sterically hindered amines leads to the formation of magnesium amides 110-112 °, reacting much faster than the parent alkyl-magnesium derivatives with C—H acidic substrates (Scheme 9). 

Here we report the use of a readily prepared polymer immobilised TEMPO as a catalyst for alcohol oxidations.15 It was derived from a commercially available oligomeric, sterically hindered amine, poly[[6-[(l,l,3,3-tetramethylbutyl)amino]-l,3,5-triazine-2,4-diyl] [2,2,6,6-teramethyl-4-piperidinyl)-imino]-1,6-hexane-diyl[(2,2,6,6-tetramethyl-4-piperidinylimino]], better known as Chimassorb 944 (MW 3000 see figure 3 for structure). This compound is used as an antioxidant and a light stabiliser for plastics. It contributes significantly to the long-term heat stability of polyolefins and has broad approval for use in polyolefin food packaging.16... 

At present, the enamines can be obtained fairly easily either in pure Z- or in pure -isomeric form and enamines derived from a series of sterically hindered amines have been prepared18-21. 

Because of the enhanced electrophUidty of the amidine carbon in A,A -bis(alkoxycarbon-yl)carboximidamide derivatives, the A,A -bis(fert-butoxycarbonyl)-l//-benzotriazole-l-carboximidamide and A(A -bis(ferf-butoxycarbonyl)-6-nitro-l//-benzotriazole-l-carboximid-amide derivatives were proposed. The latter compound proved to be the most reactive guanidinylating reagent for sterically hindered amines in solution and on solid support. 

The use of less basic and sterically hindered amines [e.g., collidine or 2,6-di-tert-butyl-4-(dimethylamino)pyridine ], the avoidance of preactivation, and the use of less polar solvent systems are additional appropriate strategies for the suppression of racemization. Except for fragment condensations in solution and couplings involving racemization-prone derivatives, the addition of HOXt to the reaction mixture has no pronounced effect on a uronium salt mediated racemization/epimerization, in contrast to the striking effects of HOAt on epimerization caused by PfPyU and haloamidinium salts such as CIP or TFFH (Section 3.8.1.2.1). 

A comparison of the results of the methylation of the pyrrolidine enamine of cyclohexanone (81 Scheme 42) with those shown in Scheme 43 for the methylation of the n-butylisobutylamine derivative (86) shows that yields are improved with the latter compound. Presumably, the more sterically hindered amine reduces the amount of iV-alkylation and retards the rate of proton transfer between the C-al-kylated iminium salt and the unreacted enamine. 

Water-immiscible amines are highly selective in the differentiation between acids (selectivity of about 10 for HCI/H3PO4 separation [44] compared to <2 in extraction by alkanols) and between them and their salts. They are widely used in extraction of metals (their anionic complexes) and of carboxylic acids, but most of them are too strongly basic for mineral acids. The convex distribution curve shows that extraction is very efficient, but back-extraction in free acid form would require huge amounts of water, resulting in extremely dilute, useless back-extracts. Only the very weak amines—highly branched trialkyl amines [52,53] or amines with at least one aryl group—combine efficient extraction with reversibility. Only few such water-immiscible aniline derivates and sterically hindered amines are currently produced on an industrial scale. Adjustment of their properties to treat a variety of feeds would require laborious synthesis. 

PP for textile applications must be stabilized. Sterically hindered amines and phenol derivatives are most often used as light and thermal stabilizers. 

The stabilizers are used to perform specific functions. Thus, there are antioxidants, viz. sterically hindered phenols [e.g., pentaerythritol ester] and/or sterically hindered amines (hydro)-peroxide decomposers, viz. phosphite [e.g., tris(2,4-di-tert-butyl phenyl)-phosphite] radical scavengers such as thio-derivatives heat stabilizers [e.g., calcium-zinc type for PVCj light stabilizers and UV blockers [e.g. aluminum flakes or carbon black] for outdoor storage and applications, etc. 

Formylation Reactions. The problem with Acetic Formic Anhydride, the most commonly used formylating agent, is undesirable side reactions, particularly if there are acid sensitive functionalities in the compound. One of the best alternatives is to use pentafluorophenyl formate (7), an easily prepared and stable compound which reacts with N-nucleophiles in minutes at room temperature to yield the IV-formyl derivative (eq 5) (Table 3). Significantly, no reaction occurs with alcohols, thiols, or sterically hindered amines. 

Primary and secondary aliphatic and aromatic amines react readily with thiiranes to give 2-mercaptoethylamine derivatives (Scheme 76) (76RCR25, 66CRV297). The reaction fails or gives poor yields with amines which are sterically hindered e.g. N,iV-dicyclohexylamine) or whose nitrogen atom is weakly basic e.g. N,A/ -diphenylamine). Aromatic amines are less reactive and higher reaction temperatures are usually required for them. The reaction mechanism is Sn2 and substituted thiiranes are attacked preferentially at the least hindered... 

According to these concepts, the reaction shown in Scheme 3.243 could be characterized by the presence of an induction period. Silyl derivatives of amines (> N-Si) are not involved in this reaction. The sterically hindered triorganosilyl substituents in BENAs (434) also should inhibit the process. 

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