Secondary amines, reactions with acetylenic

The addition of amines and ethers to alkyllithium compounds profoundly affects polymerization of such species. Amines and ethers alter the association of RLi compounds and change the course of the polymerization and its kinetics. Also, the presence of small amounts of such impurities as water, alcohols, or a-acetylenes, influences the kinetic chain length. The chain-termination reaction with such acidic protons is almost instantaneous. However, there are certain types of protons, such as a-aromatic, secondary amine, and /3-acetylenic, that are not acidic enough to react immediately but will undergo transmetalation during the course of a polymerization reaction. This results in termination or chain transfer of the polymer chain, and limits the realization of polymers of... 

Similar reactions with primary and secondary amines result in the formation of 3-aUcylamino- or 3-dialkylamino-l-butyne in 30-80% yield (TON = 3-9) [243-247]. In one example, the TOP could be estimated as 0.2 h" [246]. Enamines were proposed as reaction intermediates. It was later shown that enamines effectively react with terminal aUcynes, including acetylene, to afford the expected aminoalkynes without catalyst or, more rapidly, sometimes exothermically, in the presence of CujCf [248]. Aromatic amines do not react under the same conditions. However, in the presence of organic acids, e.g. acetic acid, 3-arylamino-l-butynes can be isolated in moderate yields (Eq. 4.59) [246, 247, 249]. 

RJ jC01CH=CH1. Vinyl carbamates of this type can be prepared by a RuClr catalyzed reaction of acetylene with C02 and secondary amines.2... 

The starting Fischer-type carbene complexes 1 were obtained by Michael addition of dimethylamine to the carbon-carbon triple bond of the corresponding ethoxy-(phenylethynyl)carbenes. In this regard, de Meijere and co-workers observed that the reactions of several primary and secondary amines with this sort of carbenes, in particular chromium derivatives 3 containing bulky substituents at the terminal carbon of the acetylenic unit, result in formation of the aminoallenylidene derivatives 5 as by-products of the expected Michael adducts 4 (Scheme 2) [20-24]. 

Reppe has shown that secondary amines of low basicity, such as carbazole, diphenylamine, indole, imidazole, and benzimidazole, and amides such as pyrrolidone react with acetylene in the presence of strong alkali to give vinyl derivatives [81, 83, 84a, b] (Eq. 30). As described by Reppe, these reactions are... 

The addition of ammonia or primary and secondary amines to acetylenes is greatly enhanced if electron-attracting groups are attached to or conjugated with the triple bond. This reaction may be formulated as in Eq. (31). 

Scheme 6.20 Reaction of acetylene with secondary amines and C02 in the presence of Ru-catalysts.

Any substitution reaction (i.e. by tertiary or secondary amines or by metallated secondary amines) is greatly facilitated when the jS-carbon carries an electron-with-drawing or simply a conjugative group. Accordingly, chlorocyanoacetylene reacts smoothly at —50° with free secondary amines to cyanoynamines, an example of push-pull substituted acetylenes (12)27... 

In the presence of copper acetylide complexes, the reaction of aldehydes with acetylene and secondary amines (eq. (2)) leads to propargylamines [6]. In contrast to the synthesis of butynediol, this reaction is catalyzed homogeneously. 

Dialkylamino-l-butynes (1), readily available from reaction of acetylene with secondary amines, are isomerized by this base to 2-dialkylamino-1,3-butadienes (2) no allenic products are observed.611... 

We further explored the steric effect of this Michael addition-cyclization reaction sequence. A series of secondary amines 13a-f were prepared and subjected to the Michael addition and acid-induced cyclization (Scheme 6) [12]. The results are summarized in Table 2. In general, we found that the secondary amines were less reactive in this Michael addition-cyclization reaction sequence. The p-toluene acetylenic sulfoxide la was not reactive enough and only the stronger electron-withdrawing o-nitrophenyl acetylenic sulfoxide 1 b achieved the transformation. In contrast to the primary amine approach, the secondary amine approach resulted in a reversed diastereoselectivity bias with compounds 14 as the major isolated products (except 13e). In general, a lower reaction temperature and increase in the steric hindrance of the secondary amine improved the diastereoselectivity. Exceptionally good diastereoselectivity was observed for the cyclization of 13 f (Scheme 6) (Table 2)... 

Several D-ribofuranosyl [113] and L-arabinofuranosyl 1,2,3-triazole derivatives [114] such as 119 have been prepared by cycloaddition of the corresponding glycosyl azide to 2-ethoxycarbonyl-2-oxoethylidene-triphenylphos-phorane, followed by reaction with methanolic ammonia or primary or secondary amines (Scheme 29). Some of prepared nucleosides proved to be potent inhibitors of HIV-1 replication. Phosphorus ylides containing an a-oxo group in the chain behave in a similar way as activated acetylenes with electron-donating groups [108[. Presimiably the azide adds to the enolate form of the ylide, followed by elimination of PhsPO [108]. 

Reactions of fluoroalkylketenimines which have been reported following these newly available synthetic approaches include hydrolysis and related additions of amines and alcohols, all of which occur at the olefinic bond. In contrast, the apparently similar addition of secondary phosphines occurs at the carbon-nitrogen double bond. These ketenimines appear to enter into cycloaddition reactions very readily with acetylenes they give quinolines, with nitrones they give oxindoles or oxadiazolidines (see p. 107), i > i and with isocyanides they yield iminoindolenines. These reactions are summarized in Scheme 54. 

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