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Shifts vinyl group

Hammond postulate, 197 hydride shift, 200 hyperconjugation, 187 Markovnikov s rule, 191 methylene group, 178 tegiospecific, 191 unsaturated, 174 vinyl group, 178... [Pg.204]

Unlike nickel Catalysts, palladium complexes do not catalyze the homo-cyclization reaction to give CDT or COD. The difference seems to be due to a different degree of hydride shift and atomic volume. With palladium catalysts, the hydride shift is easier, and hence linear oligomers are formed. The characteristic reaction catalyzed by palladium is the cocyclization of two moles of butadiene with one-hetero atom double bonds such as C=N and C=0 bonds to give six-membered rings with two vinyl groups (19) ... [Pg.176]

It has been found by NMR that carbocations la-d and 3 are prone to undergo degenerate rearrangements [automerization reactions (26)] via 1,2-shifts of the vinyl and the methyl-substituted vinyl groups (Schemes 5, 6), with... [Pg.133]

Table 1. Rates of 1,2-shifts of vinyl groups in cations la-d... Table 1. Rates of 1,2-shifts of vinyl groups in cations la-d...
When toluene solutions of 2-azabicyclo[3.2.0]hepten-4-ones were heated between 120-200°C in sealed tubes, a [1,3] shift of Cl and an ensuing decarbonylation produced dihydropyridines 220,21,130,133 an(j 3 132 either ri or r2 were vinyl groups, other [1,3] or [3,3] shifts competed successfully with dihydropyridine formation (see Sections 2.4.3.1. and 2.4.4.). The proposed intermediates of this reaction, e.g. 2-azabicyclo[2.2.1]heptenes 4 and 5 were isolated in the thermolysis of the related 3-ethoxy-2-azabicyclo[3.2.0]heptenes20-130,131,133 in toluene between 140-180°C. [Pg.554]

Dihydrobenzo[6]furan is of interest as a locked-conformation 2-vinylfuran, the conformation being opposite to that expected for a free vinyl group. Chemical shifts for the vinyl protons of 2-vinylfuran are a-H, 6.48 /3-H, 5.65,5.10 (70T1291). For the corresponding protons in the hydrobenzofuran they are a-H, 6.34 /3-H, 5.72 (77TL151). The difference is very small after allowance is made for the alkylation increments. [Pg.560]

Comparison of the chemical shift of the /3-carbon atom of the vinyl group in 6-methyl-3,4-dihydro-2//-pyran (71) with that in 2-methylenetetrahydropyran (72) indicates that p-ir conjugation is greater in the former compound, which is accordingly the more stable (78T433). [Pg.586]

I3C-NMR spectra of indoles 38 and 117 show that introduction of the vinyl group in place of the hydrogen atom greatly deshields nearly all the carbon atoms of the condensed system., 3C Signals were assigned on the basis of analysis of spectra with complete or partial l3C— H decoupling by comparison with the l3C chemical shifts of model compounds (81T3051). [Pg.271]

The NMR spectra of the diene adducts show complex multiplets in the region characteristic for H4, 8 4.1-4.7 ppm, whereas the signals for H5 are displaced downfield to the H4 region because of the presence of the adjacent vinyl group.40 The cis and trans isomers of l-aryl-5-dialkylamino-A2-1,2,3-triazolines can be differentiated on the basis of their chemical shifts for H4, which appear at 8 4.21 and 8 4.54 ppm for the cis (54) and trans compounds (55), respectively.211 NMR techniques are thus conveniently used to follow cis-trans isomerizations.211... [Pg.295]


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See also in sourсe #XX -- [ Pg.181 ]




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