Deuterium oxide, addition

The enantiomorph of this deuteroamine, prepared by decarboxylation of a-deuteroglutamate in water, does not exchange deuterium with the solvent, under the same conditions. (a-Deuteroglutamate is prepared by enzyme-catalysed racemisation of d- or L-glutamate in deuterium oxide). Additional support for the stereospecificity of enzyme-catalysed decarboxylation of amino acids comes from experiments in which tyrosine was decarboxylated in DgO to give R-a-... 

A solution of the ketone (10 mg) in dry dioxane (5 ml) is placed in the cathode compartment of the cell. Then 10% deuteriosulfuric acid in deuterium oxide (5 ml) is added slowly with stirring. A small additional quantity of dioxane may be necessary to maintain a homogeneous solution. The anode compartment is filled with an identical solvent mixture and the electrode inserted. The current is adjusted to 1(X) milliamps and the electrolysis is continued for 6-10 hr with rapid stirring. The progress of the reaction is... 

Clean sodium (0.19 g), free of paraffin or petroleum residues, is dissolved in deuterium oxide (1.2 ml) and Raney nickel alloy (0.25 g) is added in small portions over 8 min while maintaining the temperature at about 50°. When the addition is complete, the supernatant is poured off and the catalyst is washed by decantation with deuterium oxide (3x2 ml) followed by methanol-OD (2x1 ml). The catalyst should be prepared fresh as needed and the preparation carried out as rapidly as possible. 

Unlike the parent system, 5-methyl-5//-dibenz[c,e]azepine (1, R1 = Me R2 = H) on treatment with lithium diisopropyl amide fails to yield the tautomeric phenanthridine-imine (see Section 3.2.1.5.4.2.), but forms the 5-carbanion, which on quenching with deuterium oxide furnishes 5-methyl-[5-2H,]-5//-dibenz[e,e]azepine (l).83 5,7-Diphenyl-5//-dibenz[r,e]azepine (1. R1 = R2 = Ph) behaves similarly. In contrast, however, 5,7-dimethyl-5//-dibcnz[c,e]azepine (1, R1 = R2 = Me) yields theazaallyl anion 3, which on addition of deuterium oxide deuterates regiospecifically at the 7-methyl group to give derivative 4. 

The dominant factors reversing the conventional ds-hydroboration to the trans-hydroboration are the use of alkyne in excess of catecholborane or pinacolborane and the presence of more than 1 equiv. of EtsN. The P-hydrogen in the ris-product unexpectedly does not derive from the borane reagents because a deuterium label at the terminal carbon selectively migrates to the P-carbon (Scheme 1-5). A vinylidene complex (17) [45] generated by the oxidative addition of the terminal C-H bond to the catalyst is proposed as a key intermediate of the formal trans-hydroboration. 

The stereochemistry of dienes has been found to have a pronounced effect in the concerted cyclo-additions with benzyne 64>65h A concerted disrotatory cyclo-addition of tetrafluorobenzyne, leading for example with trans- (3-methylstyrene to (63, R = Me), is likely and in accord with the conservation of orbital symmetry 68>. However while the electro-cyclic rearrangement of (63, R = H) to (65, R = H) is not allowed, base catalysed prototropic rearrangement is possible. A carbanion (64, R = H) cannot have more than a transient existence in the reaction of tetrafluorobenzyne with styrene because no deuterium incorporation in (65) was detected when either the reaction mixture was quenched with deuterium oxide or when the reaction was conducted in the presence of a ten molar excess of deuteriopentafluorobenzene. 

When we allowed pentafluorophenyl-lithium to decompose in ether in the presence of an excess of N, ZV-dimethy laniline we obtained the compounds (92) 70, X = F), (94), the latter as the major compound, and a product which was shown to be (97). That this latter compound did not arise by metallation of 2V,lV-dimethylaniline followed by addition to tetrafluorobenzyne was shown by quenching the reaction mixture with deuterium oxide. No deuterium incorporation was detected. The compound (97) provides a rare example of a product derived by a Stevens rearrangement in which aryl migration has occurred b>. 

During addition of an ethereal solution of deuterium oxide (containing some peroxide) to a suspension of the organolithium reagent in pentane, a violent explosion occurred. This may have been initiated by the peroxide present, but probably... 

The ion 28 loses H2 by CID with argon to form [(PHOX)Ir(styrene)]+ (29). Compound 29 then undergoes H-D exchange with D2 gas to form the mixture of iso-topomers 29, 29-dh and 29-d2 (Scheme 13.3). When combined, these observations show that the oxidative addition of H2 to 29 is followed by alkene hydride insertion, and that both these steps occur rapidly and reversibly in the gas phase. These results thereby provide gas-phase analogues for catalytic elementary steps that are proposed to occur in solution. Support for this proposed sequence of steps was obtained from a solution-phase catalytic deuteration of styrene. Analysis showed no deuterium incorporation in the unreacted styrene at various conversions, and clean formation of dideuterio ethylbenzene as sole product. 

Using as catalyst precursors the clusters Os3H2(CO)i0 and Os3(CO)12 [71, 72], Laine and coworkers found a deuteration pattern of quinoline hydrogenation similar to that shown in Scheme 16.16, except for the presence of more deuterium in the 4-position and less in the 2-position, which has been interpreted in terms of the occurrence of oxidative addition of the osmium cluster to C-H bonds in quinoline, and also 1,4-hydrogenation (Scheme 16.17). 

L = P(OPh)3] formed by oxidative addition of DCN to ML4, coordinates one of the two double bonds of the diene. The coordination is followed by a cw-migration of the coordinated deuterium, producing a jr-allyl nickel complex in which a further cw-migration of the cyanide gave the two products 10 and 11. 

The importance of the strength of tt complex adsorption on the reaction rate through the operation of displacement effects is further demonstrated by naphthalene randomization reactions. Naphthalene exchanges very slowly with deuterium oxide. That this is due to the displacement of water by normal naphthalene and not due to a toxic side reaction, such as polymerization, is shown in randomization experiments with mono a-deuterated naphthalene. Randomization is completed within 24 hours at 120°, whereas no significant deuteration occurs under the same reaction conditions with water. This result furnishes additional proof for the dissociative exchange mechanism. 

This isomerization was used in the heteroconjugate addition to the acyclic system. Therefore, the substituted olefin 72, in which the double bond is conjugated with both sulfone and silicon atoms, undergoes a diastereoselective addition of CHsLi. The resulting lithium alcoholate is quantitatively converted into the silyl ether dianion 73 and the addition of deuterium oxide afforded the functionalized product 74 in excellent yield (equation 16. 

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