Reactions of Acetylenic Compounds

-induced addition of propan-2-ol to acetylene has been studied with and without acetone as sensitizer.168 The acetylene (241) undergoes photoaddition of isopropylamine and isopropyl ether to yield (242) and (243a) respectively.16 The same acetylene also reacts with ethyl 2-methylpropionate giving /rans-(243b) and the cyclic product (244). 

A reinvestigation of the photochemistry of diphenylacetylene has suggested that the primary photochemical process is the formation of 2-phenylbenzo-cyclobutadiene.170 This is reported to be an unstable pale-green crystalline 

Foote et /.173 have examined the photochemical addition of dimethyl acetylene-dicarboxylate to cis- and /ra/w-but-2- . Theoretically in this reaction there are seven possible [2 + 2]adducts of the general type (250). However only four 

Presumably the adducts are formed by singlet addition yielding (257) followed by a second addition. [2 + 4]Addition is also encountered yielding the photo-chemically labile 2,3-diphenylnorbornadiene. The irradiation (206 nm, pentane solution, degassed) of cyclo-octa-l,5-diyne at room temperature rapidly gave butatriene as the only product.176 

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Another unusual three-component coupling reaction involving an imine as intermediate has been developed by Ishii who has shown that a C-H bond adjacent to the nitrogen atom of an imine can be activated by an iridium complex. Carbo-metallation reactions of acetylenic compounds may then be achieved, which lead to unsaturated imines 155 (Scheme 8.67) [122]. 

Viola, A., Collins, J. J., and Filipp. N Intramolecular pericyclic reactions of acetylenic compounds. Tetrahedron., 37, 3765, 1981. 

Newman, M. S. Reactions of acetylenic compounds catalyzed by sulfonated polystyrene resins. J. Am. Chem. Soc. 1953, 75,4740-4742. 

Intramolecular pericyclic reactions of acetylene compounds in synthesis of heterocycles 81T3765. 

Dicarbonyl compounds are also formed by the reaction of acetylenic compounds with nickel carbonylates 94>. 

The insertion reactions of acetylene compounds with di-p-iodo-bis(lV, -dimethyl-l-naphthylamine-CAO-dipalladium form substituted heterocyclic products 7.29 with formation of palladium metal and the loss of one IV-methyl groups by refluxing in chlorobenzene (Eq. (7.26)) [79,82,84,85]. The heterocyclic compounds are synthesized directly by the reaction of iododimethylaminonaphthalenes with acetylenes in the presence of a catalytic amount of the 1-dimethylaminonaphthalene palladacycle, as shown in Eq. (7.27) [85]. 

Benzoselenophene [111, 112] and related fused selenophenes [113-116] were previously obtained via tedious multistep reactions involving a selenocyclization reaction from barely accessible selenium-containing compounds. Such conventional synthetic methods are unsuitable for the development of selenophene-based OFET materials. Sashida s group developed a simple one-pot preparation of benzoselenophenes by an intramolecular selenocyclization reaction of acetylene compounds with a selenolate anion [117, 118]. This allowed straightforward access to sophisticated fused selenophenes, such as 52 and 53, from commercially available chemicals [119, 120]. Scheme 6.9 depicts the key selenocyclization reaction used in the synthesis of 52. This synthetic protocol was also successfully applied to the synthesis of regioisomer 54 [121]. 

Copper tends to form more stable organocopper compounds with acetylene compounds than with aryl compounds. The synthetic reaction of acetylenic compounds with copper or copper salt, e.g., the Cadiot-Chodkiewics and Glaser reactions are well known. The Cadiot-Chodkiewics reaction is a reaction where I-bromoalkyne easily reacts with a terminal alkyne in the presence of a catalytic amount of a cuprous salt or amines to afford conjugate diacetylene compounds in high yield [43]. For example, polyacetylene is easily synthesized as shown in eq. (22.19) [43],... 

A. Viola, J. J. Collins, and N. Filipp, Intramolecular Pericyclic Reactions of Acetylenic Compounds , Tetrahedron, 1981, 37, 3765. 

CYCLOADDITION AND HETEROCYCLIZATION REACTIONS OF ACETYLENIC COMPOUNDS WITH ELECTRON-WITHDRAWING SUBSTITUENTS... 

Zeller, E. A., B. Gartner, and P. Hemmerich 4a,5-Cycloaddition Reactions of Acetylenic Compounds at the Flavoquinone Nucleus as Mechanisms of Flavo-protein inhibitors. Z. Naturforsch. 27b, 1050 (1972). 

Acylation of acetylenic compounds provides /ra/ j -P-chlorovinyl ketones (181). Vinyl cations were proposed to be the intermediates in these reactions. 

AHyHc compounds can be carboxylated readily using Ni(CO)4, either catalyticaHy or stoichiometricaHy. In the presence of acetylene, the reaction of aHyhc compounds and CO, alcohols, and Ni(CO)4 yields dienic carboxyHc esters according to the following equation (136) ... 

Reactions of acetylene and iron carbonyls can yield benzene derivatives, quinones, cyclopentadienes, and a variety of heterocycHc compounds. The cyclization reaction is useful for preparing substituted benzenes. The reaction of / fZ-butylacetylene in the presence of Co2(CO)g as the catalyst yields l,2,4-tri-/ f2 butylbenzene (142). The reaction of Fe(CO) and diphenylacetylene yields no less than seven different species. A cyclobutadiene derivative [31811 -56-0] is the most important (143—145). 

III. Reactions of Acetylenic Acids and Esters with Individual Nitrogen-Containing Heterocyclic Compounds... 

Thermal [2h-2] cycloaddition reactions of carbonyl compounds were catalyzed by a Lewis acid. The catalyst forms complexes with the carbonyl compounds and enhances the electron-accepting power. The reaction shifts from the delocalization band to the pseudoexcitation band. Catalyzed [2h-2] cycloaddition reactions were observed with acetylenic compounds [28] and ketenes [29-31]. 

The state of research on the two classes of acetylenic compounds described in this article, the cyclo[ ]carbons and tetraethynylethene derivatives, differs drastically. The synthesis of bulk quantities of a cyclocarbon remains a fascinating challenge in view of the expected instability of these compounds. These compounds would represent a fourth allotropic form of carbon, in addition to diamond, graphite, and the fullerenes. The full spectral characterization of macroscopic quantities of cyclo-C should provide a unique experimental calibration for the power of theoretical predictions dealing with the electronic and structural properties of conjugated n-chromophores of substantial size and number of heavy atoms. We believe that access to bulk cyclocarbon quantities will eventually be accomplished by controlled thermal or photochemical cycloreversion reactions of structurally defined, stable precursor molecules similar to those described in this review. 

The choice of materials, tools and apparatus has to be made only after analysing the potential reactions of the compounds with these materials. It is particularly the case when handling acetylenic compounds, unsaturates, ha-logenated derivatives. 

Alkadiene- and alkatrienephosphonates are available from acetylene-allene rearrangement of acetylene phosphites which could easily be prepared from the reaction of carbonyl compounds and 1-alkynes. 

The nitrogen atoms in ADC compounds are highly electrophilic. Nucleophilic attack on nitrogen is easy, and as with electrophilic acetylenes, such as dimethyl acetylenedicarboxylate, it seems likely that some cycloaddition reactions of ADC compounds with unsymmetrical substrates proceed via a stepwise mechanism. PTAD is a powerful electrophile, although TCNE is more reactive, and chlorosulfonyl isocyanate is more reactive still.58... 

The coupling reaction of acetylenic carbinols was also extended to the thiophene series (80). The diacetylenic glycols were of particular interest, since they provide convenient synthetic routes to bifunctional compounds difficult to prepare by other means. The coupling reaction, which took place, could be represented as follows ... 

Later authors established the approximate composition of products formed in the reaction of acetylene with sulfur at different temperatures. At 325° the composition was found to be CSj 77%, thiophene 9%, thienothiophene 1 6% at 500°, CSj 77%, thiophene 12%, and thienothiophene 1 6% at 650° CS2 83%, thiophene 5%, and thienothiophene 1 3%, with sulfur conversion being 38%, 74%, and 77%, respectively. When studying this reaction at 290°-390°, Bhatt et isolated thiophenol in addition to the above compounds but failed to increase the yield of thienothiophene 1. 

Numerous reactions of acetylenic esters are reported in the literature, and many of these lead to heterocyclic compounds. Acetylenic esters undergo very facile addition reactions with several nucleophiles and also they participate as dipolarophiles in 1,3-dipolar cycloadditions, and as... 

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