Tellurium—nitrogen bonds reactions with

Tellurium(VI)-nitrogen bonds can be generated by the reaction of hexamethyldisilazane with tellurium hexafluoride (Eq. 2.12). The product (Mc3SiNH)TeE5 is a useful precursor for a variety of NTeEs compounds. By contrast, SEe is inert towards Si-N reagents. 

The polar tellurium(II)-nitrogen bond is readily susceptible to protolysis by weakly acidic reagents. Eor example, the reaction of [Te(NMe2)2]oo with two equivalents of Ph3CSH produces the monomeric thiolato derivative Te(SCPh3)2. Alkynyl tellurides may be prepared by the reaction of terminal acetylenes with arenetellurenamides (Eq. 10.13). ... 

In this chapter, we will review the use of ylides as enantioselective organocata-lysts. Three main types of asymmetric reaction have been achieved using ylides as catalysts, namely epoxidation, aziridination, and cyclopropanation. Each of these will be dealt with in turn. The use of an ylide to achieve these transformations involves the construction of a C-C bond, a three-membered ring, and two new adjacent stereocenters with control of absolute and relative stereochemistry in one step. These are potentially very efficient transformations in the synthetic chemist s arsenal, but they are also challenging ones to control, as we shall see. Sulfur ylides dominate in these types of transformations because they show the best combination of ylide stability [1] with leaving group ability [2] of the onium ion in the intermediate betaine. In addition, the use of nitrogen, selenium and tellurium ylides as catalysts will also be described. 

The SRN1 process has proven to be a versatile mechanism for replacing a suitable leaving group by a nucleophile at the ipso position. This reaction affords substitution in nonactivated aromatic (ArX) compounds, with an extensive variety of nucleophiles ( u ) derived from carbon, nitrogen, and oxygen to form new C—C bonds, and from tin, phosphorus, arsenic, antimony, sulfur, selenium, and tellurium to afford new C-heteroatom bonds. 

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