Diastereoselective Reactions of Sulfur- and Selenium-Bridged Bisphosphaalkenes with Tetrachloro-o-benzoquinone

Abstract

2,4-Diphospha-3-thia- and 3-selenapentadienes [(Me ₃ Si) ₂ C = P] ₂ E ( 1a : E = S; 1b : Se) react as bifunctional phosphaalkenes with two equivalents of cyclopentadiene and of tetrachloro-o-benzoquinone (TOB), furnishing 2a and 2b from double [2+4] cycloaddition reactions of the diene and 3a and 3b from the reactions of TOB with the P = C double bonds. The phosphanorbornane-related chalcogenophosphinous anhydrides 2a and 2b are obtained as pairs of isomers, whereas the reactions with TOB proceed diastereoselectively. X-ray crystallographic data confirm that bis-dioxaphospholene-related 3b consists of a mixture of (RR) and (SS) enantiomers. A third equivalent of TOB can be added oxidatively to one phosphorus atom of 3a and 3b , furnishing the spirocyclic compounds 6a and 6b with P(σ < eqid1 > λ < eqid2 > ⁵ < eqid3 > ⁵ ) connectivity. 3a and 6a are configurationally stable at room temperature, whereas the selenium derivatives 3b and 6b undergo slow isomerisation in solution.

Keywords:

• Bisphosphaalkenes
• chalcogenophosphoranes
• cycloaddition
• oxidative addition
• selenobisphosphanes
• thiobisphosphanes

Acknowledgments

Dedicated to Professor Marian Mikołajczyk, CBMiM PAN in Łódź, Poland, on the occasion of his 70th birthday.

We thank Mrs. D. Döring and Dr. U. Papke (mass spectrometry) and Mrs. D. Deuse and Professor L. Ernst (NMR spectroscopy) for support.

Notes

*⁷⁷Se satellites not resolved due to overlap from signals of 2b.

**The mixture of isomers was not analyzed by ⁷⁷Se NMR.