Removal of functional groups

The reactions are radical chain processes (Scheme 3) and, therefore, the initial silyl radicals are generated by some initiation. The most popular thermal initiator is azobisisobutyronitrile (AIBN), with a half-life of 1 h at 81 °C. Other azocompounds are used from time to time depending on the reaction conditions. EtsB in the presence of very small amounts of oxygen is an excellent initiator for lower temperature reactions (down to —78°C). The procedures and examples for reductive removal of functional groups by (TMSlsSiH are numerous and have recently been summarized in the book Organosilanes in Radical Chemistry. ... 

Scheme 5.12. Reductive Removal of Functional Groups from a-Substituted Carbonyl... 

The removal of functional groups from the a-carbon of carbonyl compounds is an important transformation in organic synthesis. Anionic tellurium reagents offer additional useful methods to attain this. 

Addition or removal of functional groups Addition of functional groups to double bonds or their removal to form... 

The synthetic potential of reductions by formate has been extended considerably by the use of ammonium formate with transition metal catalysts like palladium and rhodium. This forms a safe alternative to use of hydrogen. In this fashion it is possible to reduce hydrazones to hydrazines, azides and nitro groups to amines, to dehalogenate chloro-substituted aromatics, and to carry out various reductive removals of functional groups. For example, phenol triflates are selectively deoxygenated to the aromatic derivatives using triethylammonium formate as reductant and a palladium catalyst. - These recent af li-cations have been reviewed. 

Mechanisms and catalysis chl3 Removal of functional groups Retrosynthetic analysis ch30... 

We discussed the removal of functional groups, and why you might want to do it, in Chapter 25. 

In some cases, the oxidative purification is followed by a thermal treatment that is, heating the sample to ca. 700 C in an atmosphere of argon. It helps annealing surface defects and, partially, causes a thermal removal of functional groups from the surface, too. However, it also leads to a further graphitization of the surface. Hence careful consideration is required whether graphitized or functionalized nanodiamond is more advantageous for a certain experiment or application. 

Oxidase, ligase, transferase, and hydrolase. In fact, the name oxidase is reserved for oxidations where a molecule of oxygen is present. Most oxidations encountered in metabolic pathways are catalyzed by dehydrogenase enzymes, which utilize cofactors such as FAD or NAD+ as the oxidant. Removal of functional groups without hydrolysis is done by lyase enzymes. The classihcation of enzymes is discussed in Section 8.1.3 (see Table 8.3 on page 193 of the text). 

---