Deuterium bonds compounds

The use of deuterated organosilicon hydrides in conjunction with proton acids permits the synthesis of site-specific deuterium-labeled compounds.59 126 221 Under such conditions, the deuterium atom in the final product is located at the charge center of the ultimate carbocation intermediate (Eq. 62). With the proper choice of a deuterated acid and organosilicon hydride, it may be possible to use ionic hydrogenation in a versatile manner to give products with a single deuterium at either carbon of the original double bond, or with deuterium atoms at both carbon centers.127... 

The hydroxo complex [D] is assumed to rearrange to the cr-bonded compound [A] since only a secolidary isotope effect is observed with C2D4, and if the n complex went directly to acetaldehyde Henry claims that the hydride shift involved would have produced a primary deuterium effect. Although the hydroxo complex [D] would have been expected to be traris, it was suggested that kinetically significant amounts of the cis isomer are present. 

Because of its low acidity, hydrogen cyanide seldom adds to nonactivated multiple bonds. Catalytic processes, however, may be applied to achieve such additions. Metal catalysts, mainly nickel and palladium complexes, and [Co(CO)4]2 are used to catalyze the addition of HCN to alkenes known as hydrocyanation.l67 l74 Most studies usually apply nickel triarylphosphites with a Lewis acid promoter. The mechanism involves the insertion of the alkene into the Ni—H bond of a hydrido nickel cyanide complex to form a cr-alkylnickel complex173-176 (Scheme 6.3). The addition of DCN to deuterium-labeled compound 17 was shown to take place... 

In Figure 3, quadrupole coupling constants for deuterium bonded to Mo, W, and A1 exhibit the largest percentage deviations from Eq. (13). The experimental data for those elements were obtained from compounds with uncommon structures 7r-(Cs Hs )2 MoD2, ir-(Cs Hs )2 WD2, and LiAlD4, which does not have a truly isolated A1D4 unit and Al-D bonds. 

LiAlD4 is often applied to the preparation of deuterium-labeled compounds by reduction of C=0 bonds, for example, to the preparation of isobutyl alcohols labeled in the / -, or y-position29,30 and to the reduction of biacetyl to [2,3-D2]-2,3-butanediol.31 Monodeuterated secondary alcohols are also formed by its action on alicyclic ketones,27,32,33 on deuteration of camphor34 formation of the 2-deuterated product is accompanied by that of [3-Dx]-isoborneol, which indicates that enolization occurs under the reaction conditions. 

A similar marked weakening of neighboring C-H bonds is observed also in sulfoxides88 and sulfonium salts89 and has been used for preparation of deuterium-labeled compounds e.g., the following method is recommended for... 

The fourth edition has been expanded by a chapter on the Formation of Carbon-Phosphorus Bonds and by another on the Formation of Carbon-Deuterium Bonds . The chapter on Alteration of Nitrogen Groups in Carbon-Nitrogen Compounds has been substantially expanded, but the remaining parts of the book have merely been completed by inclusion of preparative processes discovered in recent years. 

A study undertaken by Mislow et al. (1964) resulted in rates of racemization for the compounds (IV)-(VI). These all race-mized more rapidly than the undeuterated material, with 7co/ h being 1.05, 1.13, and 1.18 for (IV), (V), and (VI), respectively. It is difficult to see how these isotope effects, especially that for methyl deuteration, could arise from any cause other than the smaller steric requirements of the carbon-deuterium bond. 

The B-alkyl-9-BBN undergoes an interesting reverse reaction to afford the parent alkene when treated with benzaldehyde. Consequently, the reaction is uniquely employed for the synthesis of exocyclic olefins (Chart 24.3). The hy-droboration of cyclic olefins with an internal double bond, followed by homologation with carbon monoxide in the presence of lithium trimethoxyaluminum hydride afford B-(cycloalkylmethyl)-9-BBN. This intermediate on treatment with benzaldehyde leads to an exocyclic methylene compound (Chart 24.3) [16]. Since the synthesis proceeds from the cycloalkene, thus it provides a valuable alternative to the customary methylenation of carbonyl compounds by Wittig and related procedures. The method also provides a clean synthesis of deuterium-labeled compounds (Eq. 24.10) [16], without positional scrambling or loss of label. Consequently, methylmethylene-d -cyclopentane in 52% isolated yield is obtained. 

In the epoxidation of alkenes with peroxy acids, the stereochemistry of the groups bonded to the double-bonded carbon atoms is retained. The reaction is stereospecific, as we see in the following deuterium-substituted compounds. Groups that are cis in the alkene are cis in the epoxide, and groups that are trans in the alkene remain trans in the epoxide. 

In these two rearrangements, a hydrogen (or deuterium) atom that is a bonded at an sp -hybridized carbon atom moves from one end of a five-carbon-atom system to the other end. In the process, the locations of the alternating single and double bonds and the hybridization of the terminal atoms change. The rearrangement could not be detected without deuterium-labeled compounds because... 

A catalytic asymmetric cycloaddition reaction between norbomadiene and methylenecyclopropane can also be achieved in the presence of a [Ni(cod)2]-(—)-benzylmethylphenylphosphine catalyst to give the cycloadduct (72) in an optically active form. This reaction may proceed via a metallocyclopentane intermediate. The reactions of methylenecyclopropane with [Ni(cod)2l-phosphine systems do not appear to involve cleavage of the three-membered ring. However, the bis(acrylonitrile)nickel-catalysed cycloaddition reaction of methylenecyclopropane with methyl acrylate, which yields 3-methoxy-carbonylmethylenecyclopentane (73), does involve C—C bond cleavage. Reaction with the deuterium-substituted compound CHD=CDC02Me gives the cyclopentane derivative (74). An intermediate of the type (75) may be involved in this reaction. 

The reaction of diphenyl trithiocarbonate with phenyl-lithium, which takes place at -78 °C to form (446), constitutes a further example of a thiophilic addition to the thiocarbonyl double bond. Compound (446) appeared to be stable in solution below -20 C, and its structure was confirmed by its reactions with deuterium oxide and methyl iodide, affording (447) and (448), respectively. Dimethyl trithiocarbonate reacted with two equivalents of dimethylsulphoxonium methylide to form... 

The substitution of a heavy atom for a light one in a molecule should lead to a decrease in the frequency of vibration of the bonds to that atom with a consequent shift of the infrared absorption peak. This isotope shift has been extensively used in investigations of deuterium-substituted compounds but has been little used for other elements. 

For allyl acetate a significant deuterium isotope effect supports the hydrogen abstraction mechanism (Scheme 6,31).183 Allyl compounds with weaker CTT-X bonds (113 X=SR, S02R, Bi etc.) may also give chain transfer by an addition-fragmentation mechanism (Section 6.2.3). 

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