Monosubstituted diacetylene

The monosubstituted diacetylenes, including the 3-triethylstannyl derivative (81%) (71ZOB2230), react with the 1,3-dipole to yield a 3(5)-alkyn-l-ylpyrazole (65ZOR610 68KGS695) (Scheme 4). 

It is known that diacetylenes (in Favorsky s reaction, for example) are 1000-fold more active than monoacetylenes. It is of interest to consider how the accumulation of triple bonds will affect the compound acidity. However, in the literature there are no data on the CH acidity of diacetylenic compounds. We were the first to estimate the p/ifa of a monosubstituted diacetylene, 4-butadiynyl-l,3,5-trimethylpyrazole, to be about 24-26 log units. Unfortunately, the authors (83IZV466) have failed to determine the acidity of the diyne more accurately owing to the side processes of remetallization that complicate control over reaction. 

The reaction of disubstituted diacetylenes with hydrazine hydrate was reported by Darbinyan et al. (70AKZ640). In the first stage the addition of hydrazine to the terminal carbon atom of the diacetylene system is analogous to that of primary amines to diacetylene (69ZC108 69ZC110). With monosubstituted diacetylenes (R = H), hydrazine adds to the terminal triple bond. This leads to the formation of vinylacetylenic hydrazine 22 which cyclizes to dihydropyrazole 23 subjected to further isomerization to the pyrazole 25. It is possible that hydrazine 22 undergoes hydration to the ketone 24 which can easily be cyclized to the pyrazole 25... 

The addition of benzyl azide to monosubstituted diacetylenes initially proceeds at the terminal acetylene bond to form two regioisomeric 4- and 5-ethynyl-1,2,3-triazoles 98 and 99 along with minor amounts of the corresponding diadducts (81ZOR741 82ZOR1619). 

Until 2003 [11] no single crystal to single crystal transformation of a monosubstituted diacetylene to polydiacetylenes had been reported [27]. The Cambridge Structural Database contains only four entries for terminal diacetylenes and none of these have the supramolecular structural features necessary for a topochemical 1,4-polymerization as outlined in Scheme 5.1. There are many reasons for the lack of information on the topochemical polymerization of unsymmetrical monosubstituted diacetylenes. One is that the oxidative coupling procedure, readily applied for the preparation of symmetrical diacetylenes, is not easily applied to the preparation of unsymmetrical diacetylenes. Another factor is that unsymmetrical diacetylenes lack a center of symmetry and are less likely to pack with simple translational symmetry, a structural feature commonly observed for diacetylenes that undergo a topochemical polymerization (see Scheme 5.1). 

Scheme 5.5. The design of a supramolecular synthetic method for the preparation of a supramolecular structure with structural parameters suitable for a topochemical polymerization of a monosubstituted diacetylene.

The reaction of diacetylene or its monosubstituted homologs with guanidine in the presence of an equimolar amount of sodium ethylate (80°C, EtOH, 14 h) leads to 2-amino-4-alkylpyrimidines (33) (70ZOR1347 71ZOR14). Their structures were proved by comparison of their properties (as well as those of their picrates) with those of authentic samples obtained by independent synthesis. 

A reaction of sodium azide with l,4-dichlorobut-2-yne (diacetylene equivalent) has been described (89CB1175). When the monosubstitution product is treated with sodium hydroxide in methanol, 4-ethynyl-l//-l,2,3-tiiazole (93) is formed. 

Monosubstituted acetylenic compounds can be oxidatively dimerized by air at room temperature in the presence of copper salts in a pyridine-methanol solution. This method has been applied to a wide variety of acetylenic compounds and gives high yields in disubstituted diacetylenic compounds (equation 264).590... 

Klebanskii, A. L., Grachev, I. V., Kuznetsova, O. M. Reaction of formation of diacetylenic compounds, from monosubstituted derivatives of acetylene. I. Mechanism of formation of diacetylenic compounds. Zh. Obshch. Khim. 1957, 27, 2977-2983. 

J.B. Armitage et al, CA 47,1034( 1953)(In the prepn of monosubstituted derivs of diacetylene, a small quantity of an expl product corresponding to the formula ... 

Reactions of a-acylenaminoketones with hydrazines afforded various substituted-pyrazoles <01JHC109>. Treatment of a-benzotriazolyl-a,P-unsaturated ketones with monosubstituted hydrazines followed by alkylation at the 4-position of the pyrazoline ring afforded unsymmetrical l,3,5-triaryl-4-alkylpyrazolines and -pyrazoles <01JOC6787>. Cyclocondensations of diacetylenic ketones with hydrazines afforded alkynyl substituted pyrazoles <01JCS(PI)2906>. 

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