Page 195 - Catalysts for Fine Chemical Synthesis Vol 1 - Robert & Poignant

asymmetric hydrogenation of carbon±carbon double bonds 183

Different chlorophosphines can be synthesised, or are available from
Strem or Digital Chemicals.
. Alumina, activated overnight at 150 8C

. Two 100 mL Schlenk tubes with magnetic stirrer bars
. Ice-bath
. Sinter funnel with an inert gas inlet

Procedure
1. Two 100 mL Schlenk flasks, each equipped with a magnetic stirrer bar, were
dried at 150 8C overnight, cooled under vacuum and then flushed with
nitrogen.
2. One of the Schlenk tubes was filled with (ÿ)-(1R, 3R, 5R, 6S)-bicyclo [3.2.0]
heptan-3,6-diol (500 mg) dissolved in dry tetrahydrofuran (20 mL) under
nitrogen, then triethylamine (0.87 g) was added.
3. The solution was cooled to 0 8C in an ice-bath, and then the chloropho-
sphine (2.2 g) was added dropwise via a syringe over 5 minutes with stirring.
A white precipitate of triethylammonium chloride appeared. When the
addition was complete, the ice-bath was removed and the stirring was
continued at ambient temperature for 15 hours.
4. A sinter funnel with nitrogen inlet connected to the second dry Schlenk tube
was filled with a pad of activated alumina which was cooled under vacuum
and then flushed with nitrogen. The precipitate was filtered off through the
pad of alumina under nitrogen. The solvent was removed under vacuum
from the second Schlenk tube.
5. The solvent was removed in vacuo to give the bisphosphinite ligand (1R, 3R,
5R, 6S)-3,6-bis[bis(4 -fluorophenyl) phosphinooxy] bicyclo [3.2.0] heptane
0
as a white solid (1.99 g, 90 %).
The ligands prepared by this method were sufficiently pure for use as an
in situ catalyst preparation.
3
NMR 13 C (50 MHz, CDCl 3 ): d 30.16 (s, C 1 ); 33.80 (d, J PC 5.4 Hz, C 4 ),
3
3
3
37.04 (d, J PC 6.5 Hz, C 7 ), 40.88 (d, J PC 4.8 Hz, C 2 ); 45.43 (d, J PC 4.8 Hz
2
2
C 5 ); 69.98 (d, J PC 16.3 Hz, C 6 ); 84.78 (d, J PC 17.7 Hz, C 3 ); 115.18±116.88
(m, C 3 , C 5 , C 3 , C 5 ); 131.89±133.87 (m, C , C , C , C ); 136.99±137.83 (m,
00
00
0
0
00
0
0
00
2 6 2 6
1
C 1 , C 1 ); 163.54, 163.63, 163.71, 163.77 (4 d, J FC 247 Hz, C 4 , C 4 ).
00
0
00
0
NMR 31 P (162 MHz, CDCl 3 ): d 103.30 (s), 105.03 (s).
Mass: calculated for C 31 H 26 F 4 O 2 P 2 : m/z 568.13446; found [M] ‡
568.13466.