Diacetylene carboxylic acid

The reaction of diacetylene and its asymmetric homologs (penta-l,3-diyne, hexa-1,3-diyne) with semicarbazide (72ZOR2605) affords the amides of 3-methyl-pyrazole- 1-carboxylic acid (27) (80°C, EtONa, EtOH, 40 h). Amide 26 undergoes irreversible rearrangement to amide 27 at 80°C (EtONa, EtOH). 

OPD and o-dibenzoylbenzene (68CC1202). Benzodiazocine 166 (R = Me, Ar = P-CIC6H4), upon treatment with acetic anhydride, yields, in addition to isoindole 167 (vide supra), the benzhydrol 191 (70CJC1670). Mild alkaline hydrolysis of pyridazinobenzodiazocine 74 yielded 5-(o-aminophenyl-carbamoyl)pyridazine-4-carboxylic acid (74JCS(P 1)1022). The diazocine 192 or its saturated derivative, when condensed with diacetylene in dry benzene or without a solvent, gave heterochain polyamine 193 (70MI1). 

Air, the cheapest oxidant, is used only rarely without irradiation and without catalysts. Examples of oxidations by air alone are the conversion of aldehydes into carboxylic acids (autoxidation) and the oxidation of acyl-oins to a-diketones. Usually, exposure to light, irradiation with ultraviolet light, or catalysts are needed. Under such circumstances, dehydrogenative coupling in benzylic positions takes place at very mild conditions [7]. In the presence of catalysts, terminal acetylenes are coupled to give diacetylenes [2], and anthracene is oxidized to anthraquinone [3]. Alcohols are converted into aldehydes or ketones with limited amounts of air [4, 5, 6, 7], Air oxidizes esters to keto esters [3], thiols to disulfides [9], and sulfoxides to sulfones [10. In the presence of mercuric bromide and under irradiation, methylene groups in allylic and benzylic positions are oxidized to carbonyls [11]. 

The well-defined geometric parameters that dictate polymerizations of diacetylenes in the solid state have led Lauher and Fowler to employ principles of supramolecular chemistry to control the reaction within co-crystals. In particular, a urea derivative has been shown to self-assemble to form a hydrogen-bonded 3-array that preorganizes complementary diacetylenes for a 1,4-photopolymerization. Through the use of a derivative with lateral carboxylic acid groups (Scheme 2.3.8(a)) and a bis (4-pyridyl)acetylene as the reactant (Scheme 2.3.8(b)), a solid-state arrangement suitable for the reaction was achieved (Fig. 2.3.11(a)) [58]. Indeed, general applic-... 

The geometrical characteristics, determined by X-ray diffraction, for systems —C=C—in which acetylene is directly bonded to R = C=C (ethylenic), C==C (aromatic), C=0 (ketones and carboxylic acids), C=N and to other C=C bonds are collected in Table 5. In Table 6, we summarize the results of accurate ED studies of dimethylacetylene , vinylacetylene, propynaP and diacetylene which were designed to study the effects of conjugation in these systems. 

The use of diacetylenic rather than vinylacetylenic compounds as dipolarophiles gives directly the aromatic heterocycle by going through the stage of aromatization. Thus, the addition of H5C2OOC—C=N+—N —CeHs toH3C—C C—C=CH yields l-phenyl-5-prop-l-ynyl-l//-pyrazole-3-carboxylic acid ethyl ester (66ZOR615). 

Long-chain diacetylene monocarboxylic acid IRRAS Carboxylate-connterion interactions at AW interfaces and changes in these interactions dnring photopolymerization 1138... 

The synthesis of thieno[3,2- >]thiophene [17, 18] is shown in Scheme 3.3. The commercially available 3-bromothiophene undergoes formylation via lithiation at the 2-position and the addition of Al-formy[piperidine. Subsequent treatment of 3 with ethyl 2-sulfanylacetate affords the ester 4, which is converted to thieno[3,2- >]thiophene by hydrolysis and decarboxylation steps. The product is thus obtained in a very satisfactory overall yield of 60%. A similar method can be used to prepare thieno[2,3- >]thiophene from thiophene-3-carboxaldehyde via the carboxylic acid [19], but an attractive alternative route was published in full by Otsubo et al. [20] following a brief communication from de Jong and Brandsma [21], In this strategy, trimethylsilyl-l,3-pentadiyne is treated with potassium rerr-butoxide, butyllithium and carbon disulfide and then with ferr-butanol in HMPA, to obtain thieno[2,3-fi]thiophene in 46 % yield. The reaction sequence can be used to obtain the product in multigram quantities and the diacetylene derivative can be easily prepared from (Z)-l-methoxybuten-3-yne in 65 % yield. 

A different but related strategy to the polymerization of diacetylenes has been to use host-guest chemistry. One molecule, the host, provides the required molecular scaffold and the other, the guest, contains the diacetylene fimctionality. Reliable fimctionalities for producing the molecular repeat distance d (Fig. 1) are ureas or, better, oxalamides (29). The carboxylic acid-pyridine interaction has been used to assemble the host and the guest. 

Using the above strategy for the preparation of layered compounds the next step for the preparation of a layered diacetylene was to design a second molecular structure containing the diacetylene and necessary functionality for its incorporation into the layered hydrogen bonded network [15]. A reasonable choice is diacetylene 2 which contains the pyridine functionality, a functionality well known to hydrogen bond to carboxylic acids forming supramolecular networks [16]. 

Different attempts to lock-in the long-range orientational order of the mesophases of the copper(II) carboxylates have been reported. One of them consisted of replacing the alkanoic acid moiety with a diacetylenic acid, namely, pentacosa-10,12-diynoic acid, to lead to a new mesogenic material which can then be polymerized. The copper complexes formed exhibited a mesophase with a lamello-columnar order, which has been processed into highly ordered crystalline fibers which were polymerized by UV radiation without disruption of the mesomorphic order. The combination of fiber morphology, order, and the presence of oriented polydiacetylene networks suggest that these systems could be of some interest as optically non-linear media. 

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