Seleno ether

The selenadiazole 5 can be cleaved with butyllithium, via a nucleophilic attack, to give seleno-ether 10 in 38% yield, which decomposes on heating.93... 

Macrocyclic and polydentate thio- and seleno-ether ligand complexes of the p-block elements13... 

The availability of preparative routes giving a smaller range of seleno-ether macrocycles in reasonable yields has allowed their coordination to elements from across much of the transition metals and p-block elements to be explored. 

The naphthalene-derivatized seleno-ether macrocycles dinaphtho-[16]aneSe4> naphtho-[8]aneSe2 and naphtho-[12]aneSe3 have also been prepared. Hydrolysis of dinaphtho-[16]aneSe4 with sulfuric acid leads to formation of the ring contracted species naphtho-[8]aneSe2.103,104... 

Synthetic routes to macrocyclic ligands containing tellurium are still very limited, mainly because of the difficulties in sequentially introducing the necessary Te centres into organic fragments, the weakness of the Te C bonds and the unavailability or instability of many Te-containing analogues of the precursors for thio- and seleno-ether macrocycles. 

As an alternative to hydrozirconation of acetylenic tellurides or selenides, Dabdoub and co-workers have more recently described the first additions of the Schwartz reagent (one equivalent) to acetylenic selenide salts 51 (Scheme 4.30) [52]. Subsequent alkylation at selenium produces 1,1-dimetallo intermediates 52, which are cleanly converted in a one-pot process to stereodefined products 53. It is noteworthy that ketene derivatives 52 are of ( )-geometry, the opposite regiochemistry to that which results from hydrozirconation of acetylenic tellurides (vide supra). This new route also avoids the mixtures of regio-isomers observed when seleno ethers are used as educts. The explanation for the stoichiometric use of Cp2Zr(H)Cl in these reactions, in contrast to the requirement for two equivalents with seleno ethers, may be based on cyclic intermediates 54, in which Li—Cl coordination provides an additional driving force. Curiously, attempted hydrozirconation of the corresponding telluride salt 55 under similar conditions was unsuccessful (Scheme 4.31) (Procedure 12, p. 143). 

An analogous transposition occurs with allylic selenoxides when they are generated in situ by oxidation of allylic seleno ethers.186... 

DPSe diphenyl seleno ether H2MEHP mono, 2-ethylhexyl, phos-... 

Arsenic(III) halides function as very weak Lewis acids towards thio- or seleno-ethers (no telluroether adducts are known). The products are hydrolytically unstable and extensively dissociated in solution. In all these complexes the As—S(Se) bonds are very long, indicative of weak. 

In the conversion of 14 to 15, does thionyl bromide react with seleno ethers ... 

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