Stereospecificity in the migration of a chiral phosphinoyl group to a chiral carbon atom: X-ray crystal structure determination of reagent and product

Abstract

Rearrangement of the toluene-p-sulphonate of 3-(methylphenylphosphinoyl)-3-methylbutan-2-ol (10) gave 3-(methylphenylphosphinoyl)-2-methylbut-1-ene (12) in a stereospecific reaction. X-Ray crystal-structure determination (by direct methods from diffractometer data) on one diastereoisomer of each of these compounds showed that retention occurred in the migrating chiral phosphinoyl group and inversion in the secondary alkyl migration terminus. The major alcohol (10a) is orthorhombic, space group Pbca, with a= 9·067(2), b= 12·598(3), c= 21·877(5)Å, Z= 8. The structure was refined to R 0·049 (1596 observed reflections); mean σ in bond lengths 0·008 Å. The olefin (12a) is monoclinic, space group P2₁/c, with a= 15·923(12), b= 7·352(6), c= 10·839(8)Å, β= 100·94(2)°, Z= 4. The structure was refined to R 0·089 (1024 observed reflections); mean σ in bond lengths 0·013 Å.