Vinyl and ethynyl groups

Altoff, W., Fild, M., Rieck, H.-R, and Schmutzler, R., Synthesis and NMR spectroscopic studies of phosphorus compounds with vinyl and ethynyl groups, Chem. Ber., Ill, 1845, 1978. 

These effects are transferred through a vinyl group, and nucleophilic reagents will add to vinyl and ethynyl groups 595 (Michael reaction) ... 

Vinyl and ethynyl groups attached to an imidazole ring can be catalytically reduced to the saturated (or less unsaturated) species and cleaved by oxidation. The corresponding 4-carbaldehyde is formed in 71% yield when l-methyl-2,5-diphenyl-4-styrylimidazole is oxidized with osmium tetroxide. However, they may not react like aliphatic alkenes and alkynes not all addition reactions occur normally, Michael additions are known, and the compounds can act as dienophiles in DielsAlder reactions (e.g., Scheme 132). 

The substituent and geometric effects on the electronic spectra of silylenes are well modeled by ab initio MO calculations, in all essential respects . For some substituents such as vinyl and ethynyl groups, the MO calculations are inaccurate because of contamination of the UHF states by higher-lying triplet states. Removal of this contamination by the method of spin projection gave results in good agreement with expaimental trends ... 

Salaiin, J. R. Y. Synthesis and Synthetic Applications of 1-Donor Substituted Cyclopropanes with Ethynyl, Vinyl and Carbonyl Groups, 144, 1-71 (1987). 

As already shown, phenyl and ethynyl groups favorize the substitution. The same is apparently also true for a conjugated vinyl group (14) 30 31) and even the cyclopropane moiety (15) 32). 

The vinyl- and ethynyl-substituted compounds are able to participate in Michael addition reactions with a variety of nucleophiles, particularly if the group is attached to C-2. When the sodium salt of 2-ethynyl-l-methyIbenzimidazole is treated in liquid ammonia with an aliphatic alcohol, the vinyl ether (211) is produced, but KOH in ethanol surprisingly gives 1,2-dimethylbenzimidazole (Scheme 113) (75jouil30). 

Ganglion c Blocking Agents - A number of cyclic hindered amines substituted on the a-carbon with ethynyl, vinyl and alkyl groups have been synthesized and their antihypertensive properties compared with a corresponding series of open chain compounds. It was found that the open chain compounds were... 

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