Reactions of Diphenyl(phenylethynyl)selenonium Salts with Active Methylene Compounds and Amides:  First Isolation of Oxyselenuranes [10-Se-4(C3O)] as a Reaction Intermediate

Abstract

The reaction of the diphenyl(phenylethynyl)selenonium triflate 1a with active methylene compounds 5 and t-BuOK in THF gave furan derivatives 6. The [10-Se-4(C3O)] selenuranes 8a and 8b could be isolated from the reactions with benzoylacetonitrile 5f and with 1,3-indandione 5g, respectively, as reaction intermediates. The structures of the selenuranes 8 were elucidated by X-ray crystallography and (77)Se high-resolution solid-state NMR spectroscopy. The selenuranes 8 underwent ligand coupling on standing at room temperature or refluxing in chloroform and gave the furan derivatives 6 and the ring-opened product 9. Similarly, the reaction of 1a with benzamide 13a and pivalamide 13d in the presence of NaH in THF afforded oxazole derivatives 14.

Solid-state selenium-77 NMR

“…Collins, Ratcliffe and Ripmeester [103] characterized the selenium chemical shift tensor of trimethylselenonium iodide as part of their investigation of numerous selenium containing compounds. Diphenyl(phenylethynyl)selenonium triflate, [PhC"CSePh 2 ][OTf], was prepared from the reaction of diphenylselenoxide, Ph 2 SeO, and phenylethynyl trimethylsilane, PhC"CSiMe 3 , and the observed value of d iso , 468 ppm, is consistent with those of other hypervalent organoselenium compounds found in Table 15 [300]. Dicationic 1,5-diselenacyclooctane trifluoromethane sulfonate (structure shown in Fig.…”

“…The isotropic selenium chemical shifts, 454 and 451 ppm, for the compounds obtained, Fig. 16b and c, are similar to that of the reactant [PhC"CSePh 2 ][OTf], 468 ppm [300]. Analysis of the solid-state 77 Se NMR spectrum of diphenylselenium dichloride, Fig.…”

“…Kataoka and coworkers [300] have prepared two four-coordinate organoselenium compounds by reaction of [PhC"CSePh 2 ]…”

Conjugated Additions of Selenium Containing Enolates to Enones – Enantioselective Synthesis of δ‐Oxo‐α‐Seleno Esters and Their Facile Transformations

“…It is known that trimethyloxonium tetrafluoroborate can react with the selenides to generate the corresponding selenonium salts. [15] These reactions were employed to effect the synthesis of several heterocyclic compounds by ring closure reactions. [16] We observed that using the trimethyloxonium tetrafluoroborate, the organoselenium group can also be substituted by a hydroxyl group.…”

The Formation of Cyclopropane Derivatives Bearing 1,2‐Dicarbonyl Groups through Tandem Michael–Favorskii‐Type Reactions with(E)‐β‐Styrylselenonium Triflate

“…[8] In particular, the tandem Michael addition-cyclization route between alkynylselenonium salts and active methylene carbanions afforded highly functionalized furan derivatives. [9] These interesting results prompted us to investigate a tandem reaction of an alkenylselenonium salt involving multiple carbon-carbon bond formation to afford carbanions derived from malonates reacted with the selenonium salt to afford 1,1-dicarbonylcyclopropane compounds in good yields. a useful compound.…”