A new type of chelating biphospholene

Article abstract of DOI:10.1021/om0300474

The article discusses the preparation of chelating biphospholene. A simple synthesis of biphospholenes where the relative configurations of the various chiral centers are fixed, suggesting a possible use in enantioselective catalysis after resolution is presented. It is found that the x-ray crystal structure confirms the relative configurations of all the chiral centers.

Full text of DOI:10.1021/om0300474

1356
Organometallics 2003, 22, 1356-1357
A New Typ e of Ch ela tin g Bip h osp h olen e
Bernard Deschamps, Louis Ricard, and Franc¸ois Mathey*
Laboratoire “Hete´roe´le´ments et Coordination”, UMR CNRS 7653, DCPH, Ecole Polytechnique,
91128 Palaiseau Cedex, France
Received J anuary 22, 2003
Summary: The P-P bond of the [4 + 2] dimer of 2,5-
diphenyl-5H-phosphole, 1, reacts with IMe and then
EtOTl to give the R,â′-connected P-Me, P-OEt biphosp-
holene 3, whose chelates with [Mo(CO)4] and [Rh(cod)]+
have been characterized by X-ray crystal structure
analysis.
cleavage of the P-P bond with formation of the phos-
phine-phosphinite 34 (eq 2).
Recent work suggests that enantiopure R-connected
biphospholanes1 and biphospholenes2 display high po-
tential as chelating ligands for asymmetric catalysis. In
this communication, we wish to present a simple
synthesis of original 2,3′-connected biphospholenes where
the relative configurations of the various chiral centers
are fixed, suggesting a possible use in enantioselective
catalysis after resolution. The starting point is the
[4 + 2] dimer 1 of 2,5-diphenyl-5H-phosphole, which is
easily obtained by protonation of the 2,5-diphenylphos-
pholide ion (eq 1).3
The 31P spectrum of 3 shows the P-Me resonance at
7.9 and the P-OEt resonance at 151.0 with no P-P
coupling. The compound is further characterized as its
P,P-disulfide 4.5 The X-ray crystal structure of 4 (Figure
1) confirms the relative configurations of all the chiral
centers and shows a rather long C4-C5 (CR-Câ′) bridge
at 1.573(3) Å. The phosphine-phosphinite 3 easily
chelates Mo and Rh centers (eq 2). Complexes 5 and 66
The [4 + 2] dimerization yields exclusively the P-P
dimer, the junction is endo, and the Ph at the bridge is
probably syn to the CdC double bond, because the PdC
double bond tends to reacts with the diene on its less
hindered face opposite to the phenyl substituent at C5.
This point will be demonstrated later. The monoquat-
ernization of 1 by IMe proceeds easily and exclusively
at P2 (eq 2).
(4) This chemistry is absolutely similar to that of phosphine-
stabilized arsenium salts; see: Porter, K. A.; Willis, A. C.; Zank, J .;
Wild, S. B. Inorg. Chem. 2002, 41, 6380.
(5) The P,P-disulfide 4 was chromatographed on silica gel with ethyl
acetate and recrystallized from CH2Cl2/Et2O. 31P NMR (CDCl3): δ 68.7,
2
105.2. 1H NMR (CDCl3): δ 0.70 (t, Me), 1.40 (d, J H-P ) 12.1 Hz, Me-
3
P), 4.44 (m, CH bridge), 6.55 (dm, J H-P ) 37.4 Hz, dCHCH2). 13C
3
1
NMR (CDCl3): δ 16.00 (d, J C-P ) 7 Hz, Me), 20.45 (d, J C-P ) 52.3
2
2
Hz, Me-P), 38.56 (d, J C-P ) 11.4 Hz, CH2), 53.76 (dd, J C-P ) 14.1
1
3
and 3.1 Hz, CH), 54.97 (dd, J C-P ) 66.9 Hz, J C-P ) 6.5 Hz, CH-P),
1
3
2
56.59 (dd, J C-P ) 51.8 Hz, J C-P ) 10.3 Hz, C-P), 62.14 (d, J C-P
)
)
The 31P resonances of the starting compound (δ(31P)
2
2
7.4 Hz, OCH2), 139.44 (d, J C-P ) 22.4 Hz, dCH), 145.21 (dd, J C-P
29.1 Hz, 3J C-P ) 5.3 Hz, dCH). MS: m/z 597 (M+ + H, 50%), 313 (61%),
283 (100%). HRMS for C35H35OP2S2: calcd, 597.1605; found, 597.1604.
(6) Complex 5 was obtained by reaction of [Mo(CO)4(nbd)] with 3
and recrystallized from hexane/CH2Cl2. 31P NMR (CH2Cl2): δ 37.9,
1
(CH2Cl2) 18.4 ppm (P2), -23.1 ppm (P1), J P-P ) 200.5
Hz) are replaced by the resonances of 2 (δ(31P) +79.5
ppm (P2), -31.1 ppm (P1), 1J P-P ) 272.2 Hz). These data
clearly show that the quaternization has exclusively
taken place at P2. The crude quaternary salt 2 is treated
in situ by thallous ethoxide. The nucleophilic attack by
EtO- exclusively takes place at P1 and induces the
165.7 (d, J P-P ) 13.8 Hz). 1H NMR (CDCl3): δ 0.68 (t, Me), 1.68 (d,
2
2J H-P ) 5.1 Hz, Me-P), 4.20 (d, J H-P ) 10.7 Hz, PCHPh). 13C NMR
2
3
1
(CDCl3): δ 14.94 (d, J C-P ) 7.2 Hz, Me), 17.25 (dd, J C-P ) 16.9 Hz,
3J C-P ) 5.8 Hz, Me-P), 47.10 (s, CH2), 51.81 (dd, J C-P ) 20.1 Hz,
1
1
∑J C-P′ ) 2.2 Hz, C-P), 56.99 (dd, J C-P ) 14.3 Hz, ∑J C-P′ ) 5.6 Hz,
CH-P), 63.10 (d, 2J C-P ) 2.3 Hz, OCH2), 63.29 (t, 2J C-P_ 2J C-P′ ) 10.0
Hz, CH), 135.89 (d, 2J C-P ) 5.6 Hz, dCH), 203.45 (pseudo t, CO), 212.14
(dd, CO), 214.77 (CO), 215.17 (CO). MS: m/z 630 (M+ - 4CO, 75%),
282 (44%), 251 (100%). HRMS for C39H35O5P2Mo: calcd, 743.1014
(1) Tang, W.; Zhang, X. Angew. Chem. Int. Ed. 2002, 41, 1612.
(2) Bienewald, F.; Ricard, L.; Mercier, F.; Mathey, F. Tetrahedron:
Asymmetry 1999, 10, 4701.
(3) Charrier, C.; Bonnard, H.; de Lauzon, G.; Mathey, F. J . Am.
Chem. Soc. 1983, 105, 6871.
(
98Mo); found, 743.1015. Complex 6 was obtained by reaction of
[Rh(cod)2]+PF6 with 3 in CH2Cl2 and recrystallized from methanol/
-
CH2Cl2. 31P NMR (CH2Cl2): δ 25.5 (dd, J Rh-P ) 145 Hz, J P-P ) 47
1
2
1
2
Hz), 139.7 (dd, J Rh-P ) 159 Hz, J P-P ) 47 Hz).
10.1021/om0300474 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 03/05/2003

Communications
Organometallics, Vol. 22, No. 7, 2003 1357
F igu r e 2. ORTEP drawing of 5 (thermal ellipsoids enclose
50% of the electronic density; carbonyls have been omitted
for clarity). Significant bond distances (Å) and angles (deg):
Mo(1)-P(1) ) 2.5498(8), Mo(1)-P(2) ) 2.461(1), P(1)-C(4)
) 1.902(3), C(4)-C(6) ) 1.587(4), C(6)-C(5) ) 1.554(3),
C(5)-P(2) ) 1.850(3); P(2)-Mo(1)-P(1) ) 83.45(3), C(1)-
P(1)-C(9) ) 100.7(1), C(1)-P(1)-C(4) ) 92.4(1), C(9)-
P(1)-C(4) ) 102.5(1), C(1)-P(1)-Mo(1) ) 117.8(1), C(9)-
P(1)-Mo(1) ) 115.0(1), C(4)-P(1)-Mo(1) ) 124.11(8),
O(1)-P(2)-C(8) ) 102.6(1), O(1)-P(2)-C(5) ) 108.1(1),
C(8)-P(2)-C(5) ) 92.0(1), O(1)-P(2)-Mo(1) ) 123.51(7),
C(8)-P(2)-Mo(1) ) 115.8(1), C(5)-P(2)-Mo(1) ) 110.1(1).
F igu r e 1. ORTEP drawing of 4 (thermal ellipsoids enclose
50% of the electronic density). Significant bond distances
(Å) and angles (deg): P(1)-C(1) ) 1.808(2), P(1)-S(1) )
1.951(1), P(1)-C(4) ) 1.880(2), P(1)-C(9) ) 1.806(2), C(1)-
C(2) ) 1.329(3), C(2)-C(3) ) 1.500(3), C(3)-C(4) ) 1.553(3),
C(4)-C(5) ) 1.575(3), P(2)-S(2) ) 1.941(1), P(2)-O(1) )
1.591(2), P(2)-C(7) ) 1.796(2), P(2)-C(8) ) 1.845(2), C(8)-
C(5) ) 1.565(3), C(5)-C(6) ) 1.507(3), C(6)-C(7) ) 1.336(3);
C(1)-P(1)-C(4) ) 94.0(1), C(1)-P(1)-S(1) ) 117.71(7),
C(9)-P(1)-S(1) ) 114.42(8), C(9)-P(1)-C(1) ) 105.4(1),
C(9)-P(1)-C(4) ) 105.3(1), C(4)-P(1)-S(1) ) 117.43(7),
O(1)-P(2)-C(7) ) 104.6(1), O(1)-P(2)-C(8) ) 109.6(1),
C(7)-P(2)-C(8) ) 95.1(1), O(1)-P(2)-S(2) ) 113.67(6),
C(7)-P(2)-S(2) ) 117.43(7), C(8)-P(2)-S(2) ) 114.67(7).
with 5% of catalyst, complete hydrogenation of (Z)-
acetylcinnamic acid is achieved in less than 2 h. Further
work will be directed toward the synthesis of enan-
tiopure analogues of 3.
have both been characterized by X-ray crystal structure
analysis. The structure of 5 is given as an example
(Figure 2). The P-Mo-P and P-Rh-P angles are 83.45
and 87.65°, respectively. A preliminary testing of the
catalytic activity of complex 6 has been performed. At
room temperature in methanol under 3 bar of hydrogen
Su p p or tin g In for m a tion Ava ila ble: Text giving experi-
mental details and characterization data and tables giving
crystallographic data for 4 and 5. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM0300474