Deuterium migrations

Below — 140°C, the EPR spectrum observed was that of the cyclopropylmethyl radical. If the photolysis was done above — 140°C, however, the spectmm of a second species was seen, and above — 100°C, this was the only spectmm observed. This second spectmm could be shown to be that of the 3-butenyl radical. This study also established that the 3-butenyl radical did not revert to the cyclopropylmethyl radical on being cooled back to — 140°C. The conclusion is that the ring opening of the cyclopropyl radical is a very facile process and that the lifetime of the cyclopropyl radical above — 100°C is very short. Even though the equilibrium favors the 3-butenyl radical, the reversible ring closure can be detected by isotopic labeling experiments, which reveal the occurrence of deuterium migration ... 

Hosoya T, Uekusa H, Ohashi Y, Ohhara T, Kimura H, Noda Y (2003) Deuterium migration mechanism in chiral thiolactam formation by neutron diffraction analysis. Chem Lett 32 ... 

Cold section of exchange tower Ai tow temperatures, deuterium migrates from hydrogen sulfide gas to water... 

Product analysis of the products of photolysis or thermolysis of conformationally biased tosylhydrazone salts (72) showed that a bystander equatorial Me group promotes a geminal H-shift several times more effectively than does an axial Me.78 The observation that the primary isotope effect for axial deuterium migration was 1.5 times that for equatorial migration in (72 R1 = R2 = D, R3 = Me) invalidates the common assumption that these isotope effects are equal. 

Several chemical oxidants produce the NIH shift in the hydroxylation of 4-anisole-2H.681 Significantly, the system consisting of f-Bu02H-Mo(CO)6 induced deuterium migration the most. This reagent is known to effect many other reactions characteristic of monooxygenases. The yields obtained in these hydroxylations were not reported. 

The specificity of the enzyme for the diastereotopic hydrogen atoms at the C-l of glycerol was also determined using (1 / , 2 / )-[ 1 -2 H, ]glycerol as a substrate (see Chapter 3 for the method of preparation). Again, in spite of an isotope effect deuterium migration was observed exclusively to furnish, after chemical oxidation, ( + )-(S)-3-[2-2H,]hydroxypropionic acid (Fig. 13). 

In this reaction, no isotope effect is observed and equal amounts of allylic hydroperoxides with R configuration, resulting from deuterium migration, and the corresponding (S)-hydroperox-ides resulting from hydrogen migration, are observed which are reduced to 1. 

In the case of naphthalene and substituted derivatives, a 1,2-shift has been observed. Oxidation of the deuterium labeled naphthalene 1 gives three products, 2 4. Thus deuterium migrates to some extent from the 1- to the 2-position. 

In a series of papers, Ohashi and co-workers have used single crystal neutron diffraction to characterize the products of hydrogen(deuterium)-migration reactions that accompany isomerization of certain reactive ligands bound to bis(dimethylglyoximato)cobalt moieties upon UV irradiation, remarkably in single-crystal-to-single-crystal transfor-... 

At 650°C in a flow system, 3,7-dideuteriobicyclo[3.3.1]nona-2,6-diene undergoes a degenerate rearrangement as evidenced by deuterium migration to Cl and C5 (Scheme 10.74). ... 

Jones and Flood and their co-workers have studied in detail the rates of scrambling between hydrides and long-chain alkyl groups of rhodiiun complexes. The results of this scrambling are shown in Equations 8.22 and 8.23. They have shown that deuterium migrates from one end of the alkyl group to the other. Thus, the complex of the alkane is relatively stable, and re-addition of the alkane is much faster than dissociation of the alkane. 

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