Deuterated allyl compound

Deuteration of one end of the allyl moiety in these compounds removes the equivalence of the two positions and in place of the single line for the terminal position, two separate absorptions should appear (W). One, in the normal decoupled spectrum, is a singlet for the hydrogen substituted carbon, and the other a weak quintet for the deuterated end which would be difficult to observe. These two signals would bracket the normal singlet. If a mixture of deuterated and undeuterated allyl compound is used, therefore, two easily observable peaks should appear, one in the normal position, the other shifted. In the spectra of allyllithium and allylsodium the line from the deuterated compound appeared I and 11 Hz upfield respectively, at 0°C, of the normal lines. The potassium compound only showed a somewhat broadened line. At -80°C the separation for allyllithium was 22 Hz. 

This ratio calculated from the observations on the deuterated allyl alkalimetal compounds is O.OOUU for Li, 0.003 and perhaps half this for K. This is sufficiently smaller than the 0.1 figure quoted above to give support to the delocalized form of all these allyl alkalimetal compounds Including the lithium compound. 

Palladium deuteride 1 may act as an activator of C-H bonds at allylic positions and may form Jt-allyl palladium. Via the equilibrium between Jt-allyl palladium and alkene, H-D exchange will occur by C=C double bond migration. As shown in Scheme 5, cyclododecene was converted into the fully deuterated compound by treatment with hydrothermal deuterium oxide in the presence of Pd/C catalyst. Without Pd/C, no deuteration was observed under these reaction conditions [16]. 

Under the same conditions, several types of hydrocarbon are also converted to fully deuterated compounds. The results are summarized in Table 1. Cydooctene was also transformed into fully deuterated cydooctene without a skeletal rearrangement. As shown in entries 2 and 3, saturated hydrocarbons have also been transformed into fully deuterated compounds. As described above, an interaction between allylic C-H bonds and palladium hydride induces the H-D exchange reaction for alkenes. H-D exchange in alkanes, however, cannot be explained in this way. Direct C-H activation without assistance from any functional group may be a route to the formation of fully deuterated alkanes. 

In contrast the trans, trans acid (222) was deprotonated at the benzylic position to give the allyl anion (224), which upon protonation gave as expected, 225. It has not been possible to prove the existence of the cyclopropyl anions 219 and 223 (only in the case of the methyl ester enolates the cyclopropyl anion corresponding to 219 has been shown by deuteration to exist at — 78°C). Thus, deprotonation of cyclopropyl carbonyl compounds may be strongly dependent on the structural details of the cyclopropane, as previously demonstrated by the relative acidities of 209 and 210. 

For the more reactive allylic halides 4 a and 4 b the salt of diethyl hydrazinodicarboxylate was used as the nucleophile in preference to hydrazine.Deazetization of the resultant 4,5-dihydro-37/-pyrazoles 5 gave a mixture of alkylidenecyclopropanes 6 and 7. It should be noted that attempts to make 4-isopropylidene-4,5-dihydro-37/-pyrazole (5 b) by the more obvious route (by the reaction of diazomethane with 3-methylbuta-l,2-diene) failed. This route has been modified for the synthesis of various deuterated derivatives of 5 and used to make optically active (3/ ,57 )-3,5-dimethyl-4-methylene-4,5-dihydro-3/f-pyrazole, but all of the cyclopropanes produced from thermolysis of this compound were racemic. A similar route has also been used in the synthesis of 7,7-dimethyl-6b,7a-dihydro-7//-cycIopropa[fl]acenaph-thylene. ... 

The rates of polymerization of the deuterated analog of allyl acetate were from 1.93 to 2.09 times those of the undeuterated compound while the average MW of deuterium-containing polymer was 2.38 times greater than that produced... 

An alternative interpretation to the mechanism proposed in Scheme 7.7, could be the protonation of allenyl intermediate 13 before the addition of a new hydride, to form free allene 15. The subsequent reduction of this compound would also lead to allyl ethers 3 in a pathway fully compatible with the observed deuteration pattern. To exclude this possibility, the authors of the original work prepared allene 15 from 1-ethoxy-3-phenyl-2-propyne and BuLi, (formulate the reaction ) and treated it with NaBH4 in EtOH under the same conditions employed for compound 9. The allene 15 was recovered unchanged after several hours of reaction (Scheme 7.8). 

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