Chalcogen reaction, addition

This section will focus primarily on a comparison of these ring systems with their heavier chalcogen analogues. The first selenium derivative benzo-l,2,5-selenadiazole was prepared more than 115 years ago by the condensation reaction of selenium dioxide with 1,2-diaminobenzene (Eq. 11.12) and other benzo derivatives may be prepared in a similar manner. The parent 1,2,5-selenadiazole has also been reported. This reagent has been employed to make the tellurium analogue via treatment with ethylmagnesium bromide followed by the addition of tellurium tetrachloride (Eq. 11.13). ... 

It has, however, also been reported that the reaction of aryl ditellurides with Ni°, Pd°, and Pt° may result in the cleavage of the carbon-chalcogen bond. The oxidative addition of... 

Although the high reactivity of metal-chalcogen double bonds of isolated heavy ketones is somewhat suppressed by the steric protecting groups, Tbt-substituted heavy ketones allow the examination of their intermolecular reactions with relatively small substrates. The most important feature in the reactivity of a carbonyl functionality is reversibility in reactions across its carbon-oxygen double bond (addition-elimination mechanism via a tetracoordinate intermediate) as is observed, for example, in reactions with water and alcohols. The energetic basis... 

Larger chalcogen-phosphorus heterocycles, although less common in the literature, are accessible via a variety of synthetic routes.2,83,84 For example, the cyclic trimer (SPR)3 (R = 2,4,6-tri-tert-butylphenyl) contains a puckered six-membered P3S3 ring and is produced in the reaction of a phosphinic chloride with lithium sulfide (Equation 73).98 Additionally (R P)3Se5 (R = 2,4-di-tert-butyl-6-wopropoxyphenyl), synthesised from the oxidation of a primary phosphine with three equivalents of elemental selenium (Equation 74), has... 

The 15-membered ring Se9(N Bu)6 (6.9) is a unique member of the series of cyclic chalcogen imides (see Section 12.8.1). It was first obtained as the major product of the reaction of LiN( Bu)SiMe3 with Se2Cl2 or SeOCl2. It is also formed, in addition to smaller cyclic selenium imides, in the cyclocondensation of SeCl2 with er -butylamine in THF or from the decomposition of the sele-nium(IV) diimide BuN=Se=N Bu. ... 

Aryl iodides, in Grignard reagent preparation, 9, 35 Aryl isocyanides, chalcogen—chalcogen additions, 10, 752 Aryl isonitriles, in insertion reactions, 1, 106-107 Aryl ketones, via intramolecular G—H functionalizations,... 

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