N-Hexyl amine

An early example of this strategy is the palladium black catalyzed conversion of (Z)-2-buten-l,4-diol with primary amines (cyclohexyl amine, 2-aminoethanol, n-hexyl amine, aniline) at 120 °C to give iV-substituted pyrroles in 46-93% yield [119]. Trost extended this animation to the synthesis of a series of N-benzyl amines 169 from the readily available a-acetoxy-a-vinylketones 168 [120]. This methodology allowed for the facile preparation of pyrrolo-fused steroids. 

Fig. 7. Conversion-time curves for polymerization of NCA s (0.224 mole l l) with amines (0.015 mole l-1) at 25 C in iV.iV-dimethylformamide. O y-Ethyl-L-glutamate NCA-di-isopropylamme A y-Ethyl-L-glutamate NCA-n-hexyl-amine Q Sarcosine NCA-di-isopropylaraine Sarcosine NCA-n-hexylamine. (Reprinted from paper by C, H. Bamford, and H. Block Polyamino Acids, Polypeptides and Proteins, p, 65, Wisconsin University Press 1962 (Fig. 7)3...

The discovery of high molecular-weight synthetic polypeptides came as a result of systematic studies by Blout and his co-workers of the conditions which limit the degree of polymerisation of products formed by polymerisation of NCA. Contrary to previous beliefs, it was found that the polymerisation initiated by n-hexyl amine in dry dioxane yields polypeptides of higher molecular weights than expected from the monomer-to-initiator ratio, provided M/I < 100. It should be stressed again that this observation demonstrates that some additional modes of propagation contribute to the reaction, i. e. the "simple poly-addition mechanism cannot account in toto even for the polymerisation initiated by primary amines in dioxane. 

The different behaviour of, e. g., di-isopropyl amine and n-hexyl amine now becomes explicable. The sterically unhindered n-hexyl amine mainly functions as a Lewis base which adds to the Lewis acid (the NCA) and initiates the simple amine-propagated polymerisation. On the other hand, the sterically hindered di-iso-propyl amine is inefficient as a Lewis base but, being a more powerful Bronsted base than n-hexyl amine, it initiates a rapid polymerisation resulting from the proton abstraction and the "activation of the monomer. This is seen in Fig. 7 (see also p. 19). 

The IR studies of Idelson and Blout (53) demonstrated that in dioxane the initially-formed polymer possessed a random-coiled structure (described by the authors as the /3-form). As the reaction proceeded a new material appeared, which was identified through its IR spectrum as the a-helix. This stage of the process coincided with the onset of a fast reaction. By using a deuterated n-hexyl amine as the initiator a labelled /S-peptide was prepared. This was used in turn to initiate further polymerisation which yielded an a-peptide. The isolation of the latter and its analysis proved that the a-peptide contained the expected percentage of deuterium, and hence the /S-polymer had to be the precursor of a-peptide. 

Pritzkow and Mahler studied the four isomeric azido n-heptanes and obtained directly information concerning the migratory aptitudes of different aUcyl groups. Contrary to earlier observations , they found that n-hexyl migration did occur (10-30%) to give n-hexyl-amine after hydrolysis. The secondary heptyl azides also gave rise... 

The Buchwald series of bulky phosphines containing the tunable bi-aryl moiety have also been shown to allow for the efficient animation of aryl chlorides as well.57 In particular, Pd/L3 catalyzed the reaction between secondary cyclic amines and most aryl chlorides at 80 °C, Secondary acyclic amines and anilines tend to couple best with neutral to electron rich aryl chlorides. Primary aliphatic amines are quite limited to either the amination of o-tolyl chlorides, or more activated primary amines such as benzyl amine. A better ligand for this transformation was reported to be L4 as the amination could be conducted at room temperature in many cases.58 Base sensitive R1 required the use of K3PO4 rather than NaOf-Bu. Most amines work well with this catalyst system, except for unactivated primary aliphatic amines (e.g., n-hexyl amine). Allyl amine, hydrazines, imines, benzyl amine, and (EtO)2CH2NH2 all couple well with aryl chlorides under the... 

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