Mono-substituted acetylenes

After reaction for 15 min, the band near 3295 cm (not shown in Fig. 13) decreased significantly in intensity, indicating that the mono-substituted acetylene groups were reacting. New bands also appeared near 1539 and 1512 cm . After reaction for 30 min, several additional bands appeared near 1011, 1030, 1085, 1232, 1320, 1430, and 1515 cm. The bands near 1011, 1030, 1085, 1232, 1320, and 1430 cm were clearly related to the benzothiazole sulfenamide fragment of DCBS while the band near 1539 cm was related to zinc stearate. 

The use of dispersed or immobilized transition metals as catalysts for partial hydrogenation reactions of alkynes has been widely studied. Traditionally, alkyne hydrogenations for the preparation of fine chemicals and biologically active compounds were only performed with heterogeneous catalysts [80-82]. Palladium is the most selective metal catalyst for the semihydrogenation of mono-substituted acetylenes and for the transformation of alkynes to ds-alkenes. Commonly, such selectivity is due to stronger chemisorption of the triple bond on the active center. 

The usefulness of this lithium salt as an intermediate in organic synthesis has been recently extended by the reaction with acetylene and mono-substituted acetylenes (64). At — 70 C 2 moles of lithium salt add to 1 mole of acetylene to give, after hydrolysis, a high yield of 1,4-diketone. The same reaction carried out at — 30° C produces, in addition to the 1,4-diketone, a smaller yield of a y-lactone. 

Condensation of 2-chloro- or 2,3-dichloroquinoxalines with mono-substituted acetylenes, e.g. phenylacetylene, in the presence of a palladium complex, e.g. bis(triphenylphosphane)-palladium(II) chloride and copper(I) iodide, gives mono- and dialkynylquinoxalines in good yield, e.g. 2,3-bis(phenylethynyl)quinoxaline. ... 

Recently. Shirakawa et al. also synthesized mono-substituted acetylenes with liquid crystallinemoieties by Ziegler—Natta and metathesis catalysts (see Chart... 

It is well established that the C=C stretching vibrations of mono-substituted acetylenes, C-C=C-H is observed in the infrared spectra as an absorption band in the range of 2100-2150 cm with medium intensity. The corresponding vibrations of the disubstituted acetylenes C-C=C-C proceed without change in the dipole moment of their triple bonds and, therefore, they are usually not active in the infrared spectra. If active, their absorption bands have very low intensity. In good agreement, the absorption band at 2117 cm with medium intensity in the infrared spectrum of the monomer, which corresponds to the Cs.C stretching vibrations of its triple bonds, practically disappears in the spectrum of the polymer. 

Ryden and Marvel have reported that sulfur dioxide reacts with mono-substituted acetylenes in a 1 1 ratio to yield a polymeric product [54]. No satisfactory yields of polymers were obtained from either of the following type... 

CP2C0 catalyses the condensation of acetylene and mono-substituted acetylenes (but not di-substituted acetylenes) with nitriles at 150° to give 30-70% yields of substituted pyridines [WakatsuM Yamazaki Synthesis 26 1976], This synthesis has been applied successfully in a 2+2+2 cycloaddition reaction between di(trimethylsilyl)propargyl ether and acetonitrile to prepare a pyridine intermediate whieh was used to obtain pyridoxine (vitamin Be) [Greiger et al. Helv Chim Acta 67 1274 1984. ... 

Various optoelectronic and related properties of polymers from mono-substituted acetylene monomers have been studied extensively, such as photoconductivity, nonlinear optical properties, photo and electroluminescence, electrochromism, liquid-crystalline structures, helical structures, and stimuli-responsiveness [2, 3, 6, 7]. It is noteworthy that helical structures and stimuli-responsiveness using the change of the helical structure have progressed considerably in this decade [20, 21]. Yashima s induced circular dichroism... 

Mono-substituted acetylenes can therefore be readily differentiated from double-bonded and saturated materials by the examination of this region. The only other groupings likely to absorb in the same region are bonded OH and NH groups. These can be readily differentiated by their broad appearance, and in any case confirmation of the acetylenic structure can be obtained by reference to the C C stretching region. 

Yet another reaction course is possible with mono-substituted acetylenes and carbene complexes, equation (23). A correlation between values in cyclic... 

The organocobalt catalysed synthesis of substituted pyridines from alk-l-enes and nitriles (Equation 22) has been extended further by the discovery that the leaction is catalysed by cobaltocene, Co(i7 -05145)2, a more easily obtained complex than earlier catalysts.Acetylene reacts with substituted nitriles to give 2-sub-stituted pyridines in up to 60% yield, whereas mono-substituted acetylenes react to give mixtures of 2,4,6- and 2,3,6-trisubstituted pyridines in moderate yield. 

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