For the deprotection leading to the actual compound of formula (9), with E=(CH2)3 and GF=4-vinyl-benzylamine, a solution of 1,1′,2,2′-tetrakis(diphenyl-phosphino)-4-[4-(1,3-dioxan-2-yl)-2-methylbut-2-yl]-4′-tert-butylferrocene (0.1 g, 88 μmol) in 20 ml of THF is admixed with 5 ml of 2N hydrochloric acid solution. The solution is placed under microwave radiation (125 W) according to the following program: temperature rise 10° C./min to 120° C., then plateau at 120° C. for 10 min. After cooling, the reaction mixture is concentrated under vacuum, diluted with 20 ml of water, and extracted with 2 times 25 ml of CH2Cl2. The organic phase is dried over MgSO4 and concentrated under reduced pressure. The crude product obtained is purified by chromatography on silica gel (eluent AcOEt/heptane 1:4) to give 90 mg (ρ=90%) of 1,1′,2,2′-tetrakis(diphenylphosphino)-4-(4-oxo-2-methylbut-2-yl)-4′-tert-butylferrocene in the form of a red powder, for which the 31P NMR spectrum preserves, as expected, the ABCD spin system appearance, with slightly modified chemical shifts.
