C-D Bond Formations

Incorporating deuterium into organic molecules is highly useful for the detection and identification of metabolites and decomposition products of bioactive molecules. Therefore, deuterating reactions such as H/D exchange have been used for many environmental and pharmaceutical applications [155], Moreover, molecules with C-D bonds are helpful for analyzing transition metal-catalyzed reactions [156, 157]. 

SCHEME 23.49 C-H deuteration of C-H bonds with Crabtree s catalyst 27. 

65 to 99% D incorporation SCHEME 23.50 H/D exchange with weakly coordinating directing groups. 

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Descriptions of C—D bond formation are found in treatises on synthetic organic chemistry e.g., in the complex deuteride reductions ... 

Most radical reactions involve H-abstraction as the chain terminating process and hence C-H bond formation. However, here we discuss only processes leading to direct C-H/C-D bond formation and with synthetically useful applications in the carbohydrate field. 

Hydrolysis of (CH3CHDO)4B in H2O leads to the formation of ethanol retaining the C—D bond formed in the preceding step while forming an O—H bond... 

Morrison and Migdalof (Ref 14) irradiated o-nitrotoluene and p-nitrotoluene with a Pyrex-filtered mercury lamp using D20 and p-dioxane as solvents. C-D bonds formed with o-nitrotoluene, with no C-D formation for p-nitro-toluene - ... 

In the case of terminal alkynes having oxygenated functions in the linear chain (Scheme 10, route D), Martin, Padron, and coworkers found that homopropargylic alcohols reacted properly, yielding 2-substituted dihydropyrans as sole products, probably via a Prins-type cyclization. This cyclization provides a new approach toward 2-alkyM-halo-5,6-dihydro-2//-pyrans through a concomitant C-C and C-O bond formation (Scheme 21) [35]. 

The first gold catalyzed C-S bond formation was demonstrated in a route to the 2,5-dihydrothiophene 16 via cycloisomerization of the allene 17 which occurred with high chirality transfer (d.r. > 95 5) <06AG(E)1897>. 

H shift more readily occurs with loss of nitrogen.22 Excited diazirines decay by fluorescence, carbene formation, or 1,2-H(D) migration coupled with N2 loss. C-D bonds are stronger than C-H bonds, so that deuteration retards the latter pathway and therefore RIES, leading to an increase in both fluorescence and carbene formation from 35-d6 22... 

Our approach for the total syntheses of carbazomycins A (260), B (261), C (262), D (263), and E (264), based on the iron-mediated construction of the carbazole framework by consecutive C-C and C-N bond formation, leads to the iron complex salts 602 and 779 and the fully functionalized arylamines 780a-c (607-610) (Scheme 5.84). 

D. O Hagan, M. Onega, Fluorinase mediated C- F bond formation, an enzymatic tool for PET labelling, Chem. Commun. (2006) 652-654. 

The molecular mechanism of the selective oxidation pathway is believed to be the one shown in Scheme 2 (Section I). Adsorbed butene forms adsorbed 7r-allyl by H abstraction in much the same way as xc-allyl is formed from propene in propene oxidation (28-31). A second H abstraction results in adsorbed butadiene. Indeed, IR spectroscopy has identified adsorbed 71-complexes of butene and 7t-allyl on MgFe204 (32,33). On heating, the 7r-complex band at 1505 cm 1 disappears between 100-200°C, and the 7t-allyl band at 1480 cm-1 disappears between 200-300°C. The formation of butadiene shows a deuterium isotope effect. The ratio of the rate constants for normal and deuterated butenes, kH/kD, is 3.9 at 300°C and 2.6 at 400°C for MgFe204 (75), 2.4 at 435°C for CoFe204, and 1.8 at 435°C for CuFe204 (25). The large isotope effects indicate that the breaking of C—H (C—D) bonds is involved in the slow reaction step. 

Senn HM, O Hagan D, Thief W (2005) Insight into Enzymatic C-F Bond Formation from QM and QM/MM Calculations. J Am Chem Soc 127 13643... 

Martarello L, Schaffrath C, Deng H, Gee AD, Lockhart A, O Hagan D (2003) The First Enzymatic Method for C-18F Bond Formation The Synthesis of 5 -[18F]-Fluoro-5 -deoxy-adenosine for Imaging with PET. J Label Compd Radiopharm 46 1181... 

Deng H, Cobb SL, Gee AD, Lockhart A, Martarello L, McGlinchey RP, O Hagan D, Onega M (2006) Fluorinase Mediated C-18F Bond Formation, an Enzymatic Tool for PET Labelling. Chem Commun 652... 

The naphthalene cation radical can react with the hydrogen atom. The 1-hydronaphthalene cation resulting from this reaction is more stable than the reactants. This process has no activation barrier. After its formation, the 1-hydronaphthalene cation can absorb a photon and lose one of the two hydrogen atoms on carbon 1, since these hydrogens are more weakly bound than the aromatic hydrogens. Because the C-D bond is slightly stronger than the C-H bond, the reaction mentioned here can lead to some deuterium enrichment (Bauschlicher 1998). 

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