Reaction Steps
A Schlenk flask was charged with KH (0.524 g, 13.1 mmol), and dry THF (13 mL). Di(p-tolyl)phosphine (2.331 g, 10.9 mmol) was added, and the solution turned red in colour. The solution was stirred for 30 min, and then cooled to −78° C. Bromoacetadehyde diethyl acetate (1.68 mL, 10.9 mmol) was added over 20 min, and the solution turned yellow. The solution was warmed to room temperature and 48% HBr (2.5 g, 14.8 mmol) was added. A white precipitate formed, and the solution turned colourless. The mixture was heated at 45° C. for 2 hours, and then left in the freezer overnight. The precipitate was filtered off and washed with 15 mL cold H2O, as well as 15 mL of a 1:1 mixture of cyclohexanol:ethyl acetate. The precipitate was then recrystallized in MeOH and ether, and dried under high vacuum. Yield: 2.698 g, 87.8%. Diastereomer 1: 1H NMR (CD3OD, 400 MHz, δ): 8.06 (dd, J=8.2, 12.3, aromatic CH, 4H), 7.63-7.58 (m, aromatic CH, 8H), 7.48 (dd, J=2.5, 8.2, aromatic CH, 4H), 6.19 (dd, J=6.8, 21.5, PCH(OH), 2H), 4.37-4.15 (m, H1 of PCH(OH)CH2, 2H), 3.99-3.81 (m, H2 of PCH(OH)CH2, 2H), 2.53 (s, CH3, 6H), 2.44 (s, CH3, 6H). 31P NMR (CD3OD, 400 MHz, δ): 11.12. 13C NMR (CD3OD, 400 MHz, δ): 146.8 (aromatic C—P), 146.7 (aromatic C—P), 133.7 (aromatic CH), 133.1 (aromatic CH), 130.6 (aromatic CH), 130.4 (aromatic CH), 113.9 (CH3C), 113.0 (CH3C), 61.1 (PCHOH), 22.1 (PCH2), 20.5 (CH3), 20.3 (CH3). Diastereomer 2: 1H NMR (CD3OD, 400 MHz, δ): 7.96 (dd, J=8.3, 12.5, aromatic CH, 4H), 7.86 (dd, J=8.3, 12.0, aromatic CH, 4H), 7.63-7.58 (m, aromatic CH, 4H), 7.56 (dd, J=3.2, 8.3, aromatic CH, 4H), 5.80 (ddd, J=2.5, 9.4, 16.3, PCH(OH), 2H), 4.37-4.15 (m, H1 of PCH(OH)CH2, 2H), 3.99-3.81 (m, H2 of PCH(OH)CH2, 2H), 2.50 (s, CH3, 6H), 2.49 (s, CH3, 6H). 31P NMR (CD3OD, 400 MHz, δ): 16.06. 13C NMR (CD3OD, 400 MHz, δ): 147.5 (aromatic C—P), 146.9 (aromatic C—P), 133.3 (aromatic CH), 132.9 (aromatic CH), 131.3 (aromatic CH), 130.5 (aromatic CH), 112.5 (CH3C), 111.7 (CH3C), 62.2 (PCHOH), 23.6 (PCH2), 20.4 (CH3). Anal. Calcd for [C32H36P2O2][Br]2[CH3OH][H2O]: C, 54.71; H, 5.84. Found: C, 54.65; H, 6.04. MS (ESI, methanol/water; m/z+): 257.1 [C32H36O2P2]2+. The diastereomeric excess was found to be 13%, as determined by 1H NMR, and 31P NMR.
