Selenoxanthones

By treating an equimolar mixture of telluroxanthone and selenoxanthone with Zn powder in boiling HO Ac and concentrated HCl (100 1.25) for 1 h, a reductive dimerization takes place giving the dimerized prodncts in the ratio 21 35 in addition to telluroxanthene and selenoxanthene. ... 

When diphenyl selenide di-o-carboxylic acid (II) interacts with concentrated sulphuric acid two products are obtained, selenoxanthone-carboxylic acid (I) and a dilactone (III). The latter may be considered... 

Relatively little is known about the photochemistry of phosphorus containing organic substrates. Continuing our photochemical work on compounds of structure 1a and b which leads to thio- and selenoxanthones 3a,b via thiol ester-thiopyrone-, selenol ester-seleninone-transformations ( 1, 2, 3), or photo-Friedel-Crafts-reactions ( 3-6J, respectively, "(ScFeme 1) we have extended our interest to aroyl diphenyl phosphines 1c - k (Schemes 2-5) in which X in 1a and b stands for P-phenyl. 

Ab initio molecular mechanics calculations have been used to examine the electronic states of selenoxanthene 9 and selenoxanthone 10. These results were used to explain differences in the formation of bromine adducts of these compounds (see Section 7.11.6.1.2) <1998JOC8373>. Bond dissociation enthalpies and adiabatic ionization potentials of phenolic antioxidants containing selenium and tellurium have been carried out using DFT models in an attempt to design novel vitamin E analogues such as 11 <20060BC846>. 

Reaction of selenoxanthene 9 with bromine affords the selenium addition product 72 (Equation 26) however, selenoxanthone 10 reacts with bromine to form a molecular complex 73 (Equation 27). The explanation of this difference in reactivity is based on the differences in ionization potentials of selenium in these molecules which were determined using penning ionization electron spectroscopy <1998JOC8373>. These results are consistent with ab initio calculations of the electronic states of the precursors (see Section 7.11.2). 

---