Alkynes spectroscopic analysis

The second sapphyrin analog reported by Sessler and coworkers is derived directly from macrocycle 6.26. Here, subjecting the alkyne-containing macrocycle 6.26a to Lindlar reduction conditions was found to afford a near quantitative conversion to the partially reduced macrocycle 6.27a (Scheme 6.3.3). As inferred from H NMR spectroscopic analysis, the specific structure of this reduction product is the tra 5-alkene 6.27. This compound may formally be regarded as being a true isomer of pentaazasapphyrin, and is thus referred to as [22]sapphyrin-(2.1.0.0.1) or [22]pentaphyrin- 2.1.0.0.1). 

Spectroscopic analysis of alkynes and dienes is discussed in Secs. 13.15-13.16.)... 

For the final part (Scheme 5.3), the 20-carbon chain of fumonisin Bj was coupled from the Uthium acetylide derived from 273 and the Weinreb amide 279 (233). After enantioselective reduction of the alkynyl ketone 281 (234, 235), the C-10 stereochemistiy was set, followed by benzyl ether formation and acid-catalyzed acetonide removal, to provide diol 282 (236). Using tricarballylic acid dibenzyl ester, the two hydroxy groups were esterified (237) and the hydrogenation of the azide, the alkyne, and the benzylic ethers led to the target product, fumonisin Bj (249). The spectroscopic analysis matched with those of commercial fumonisin Bj and further experiments on the synthetic material showed inhibitoiy activity on sphingoUpid biosynthesis. 

In general, in Part II we apply the same pattern of analysis to the numerous published vibrational spectra derived from the adsorption of alkynes, alkanes, and aromatic hydrocarbons. In addition, we summarize recently obtained spectroscopic results characterizing hydrocarbon species obtained by thermal, photochemical, or electron-bombardment dissociation of halogen- or nitrogen-substituted alkanes on single-crystal metal surfaces. The hydrocarbon surface species so obtained are normally as anticipated from the replacement of the heteroatoms by surface metal atoms. The... 

In this article (Part I) we have comprehensively reviewed the structural implications of the vibrational spectroscopic results from the adsorption of ethene and the higher alkenes on different metal surfaces. Alkenes were chosen for first review because the spectra of their adsorbed species have been investigated in most detail. It was to be expected that principles elucidated during their analysis would be applicable elsewhere. The emphasis has been on an exploration of the structures of the temperature-dependent chemisorbed species on different metal surfaces. Particular attention has been directed to the spectra obtained on finely divided (oxide-supported) metal catalysts as these have not been the subject of review for a long time. An opportunity has, however, also been taken to update an earlier review of the single-crystal results from adsorbed hydrocarbons by one of us (N.S.) (7 7). Similar reviews of the fewer spectra from other families of adsorbed hydrocarbons, i.e., the alkynes, the alkanes (acyclic and cyclic), and aromatic hydrocarbons, will be presented in Part II. 

When both termini of the triene are alkynic units,the reaction takes place via a diradical intermediate. Heating of (Z)-l,6-dideuteriohex-3-ene-l,S-diyne (363) at 3(X) C caused r id scrambling of the deuterium label to give exclusively a mixture of (363) and the 3,4-dideuterio isomer (365). Also, when heated in different solvents, products of typical radical reactions were observed. These data together with detailed kinetic analysis and spectroscopic studies have led to the hypothesis of the intermediacy of the 1,4-dehydrobenzene diradical (364) (p-tenzyne) in the process. ... 

The triple bonded organic functional groups considered in the present chapter are —CC—, —CN, —CNO (nitrile oxide), —OCN, —SCN and —N2. Some isomeric functions such as —NC, —NCO and —NCS, will also be included, as they sometimes occur together with their isomers. The general aspects and specific methods for the analysis of alkynes, nitriles, diazonium compounds, cyanates and thiocyanates, and other related functional groups were adequately described in previous books of the series The Chemistry of Functional Groups, Consideration was made there of detection and determination by means of chemical reactions and application of characteristic spectroscopic properties of the groups. 

We have applied cross-coupling reactions of alkynes and aryl bromides to prepare the structurally well-defined polybinaphthyl crown ethers. A racemic binaphthyl crown ether monomer roc-75 [18,62] is polymerized with roc-33 in the presence of tetrakis(triphenylphosphine) palladium(O) and copper iodide to generate a polybinaphthyl crown ether 76 (Scheme 32). This polymer is soluble in organic solvents and has been characterized by various spectroscopic methods. GPC analysis shows that 76 has a molecular weight of 30,000 and M = 12,000 (PDI = 2.4). The UV spectrum of the polymer shows the maximum absorptions - max = 246, 300, and 354 nm. 

The synthesis and X-ray ciystal structure of the nickel(O) alkyne compound [Ni(bipy)(Ti2-PhCCSiMes)] has been leported i. Comparison of spectroscopic and structural data for a series of mono-alkyne complexes indicated that NMR and IR spectroscopies are better suited to characterise the nature of the complexed alkyne (two- or four-electron donor) than X-ray structure analysis. 

Xia et al. [39] have found that out of these three catalysts only the Cu-CPSIL is effective for the reaction of aliphatic bromides with sodium azide and alkyne to produce 1,2 -triazoles under the optimized condition as the copper on CPSIL showed high dispersion and the interaction between the copper and support is different in case of Cu-CPSlL than the other two as evidenced by the X-ray photoelectronic spectroscopic (XPS) analysis. Based on experimental evidences and literature reports [40,41]/ they provide a possible pathway for this transformation as depicted in Scheme 23. 

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