A simple route to an enantiomerically pure diphosphine ligand containing a phosphorus stereogenic centre.

Asymmetry Vol. 5. No. 7. pp. 1167-l 170. 1994 ElpetitieoceLkl Printedin Great Britain 0957416684 57.00+0.00

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0957-4166(94)00156-

A Simple Route To An Enantiomerically Pure Diphosphine Ligand Containing a Phosphorus Stereogenic Centre. Beng-Hwee of Chemistry,

Department

Abstract:

The

Pak-Hing Udvcrslty

National

(+)- and (-)- forms

phospbabicyclo[2.2.l]bept-2ene

Aw,

of

Singapore,

Singapore

via an asymmetric Diels-

and 1-phenyl-3.4dimetbylphosphole

and (S)-(+)-bis(p-chloro)bis[

naphthalenyl-C,Nldipalladium(U),

0511.

of S-(diphenylphosphino)-2,3-dimethyl-7-phenyl-7-

have been prepared enantioselectively

Alder reaction between diphenylvinylphosphiiae using 0.5 equiv of (R)-(-)-

Leung+

(DMPP)

I-[ I-(dimethylamino)ethyl]-2-

respectively, as the chiral catalyst. The enantiomeric purity of

the dipbosphine ligand has been confirmed by *H and 3tP NMR studies. Optically active phosphine homogenous

asymmetric

catalysis.’

ligands have been successfully

employed

as metal-based

auxiliaries for

For most of these ligands, the chirality resides either at the phosphorus

donor atoms or in the carbon skeleton.2 The title ligand, 1. belongs to the rare. class of diphosphines carry botb of these desirable structural features. The availability of the enantiomerically

which

pure forms of 1 may

therefore have important bearings on the future design of chiral catalysts.

The racemic form of 1 has been prepared diastereoselectively reaction

between

[M(Ph2PCH=CH&X2]

and [M(DMPP)2X2]

in high yields from the Diels-Alder (where M = Pd, pt, X = Cl, Br, I).3 In

principle, it is possible to resolve this bidentate ligand into its optical antipodes using established methods such as formation of a pair of diaste.reomeric phosphonium however,

resolution

thermodynamic

is a tedious

and inefficient

instability of the uncoordinated

this paper we offer an attractive diphenylvinylphosphine dipalladium(II) complex

approach

and DMPP 27.

salts4 or by means of metal complexation.5 process.

In this case, it is further

In general,

hampered

by the

phosphorus stercogenic centre at the bridgehead position.6 of generating

via an asymmetric

(Scheme 1).

1167

the optically Diels-Alder

pure forms of 1 directly reaction

mediated

In

from

by the chiral

B.-H. Aw and P.-H. LEUNG

1168

DMPP

Scheme Diphenylvinylphosphine This mono nuclear complex acetonitrile

yielded

dichloromethane was complete

(-)4.

was coordinated

regiospecifically*

was isolated as stable yellow needles. Upon removal

of silver chloride

and then treated with a stoichiometric in 5 hours. The resulting

complex

to (-)-2 to give (-)-3 in quantitative Treatment

and excess

amount

of (R)-3 with silver perchlorate

acetonitrile,

(-)4

was redissolved

of DMPP at room temperatumto

(-)-5 was subsequently

yield.9

isolated

as pale yellow

in in

The reaction needles

from

ether with [a]~ -56.3 ( c = 1.O, CHCl3) in 70 % yield.9

chloroform-diethyl

ligand (+)-1 was liberatedfrom (-)-5 in two steps as illustrated

The free disphosphine perchlorate

1

salt was first decomposed

complex

was isolated

aqueous

potassium

as stable yellow

cyanide

afforded

quantitatively prisms

to (+)-6 with concentrated

hydrochloric

in Scheme

with [o(]D +10.9 ( c = 1.0, CH2C12).9 Treatment

of (+)-6 with

the free ligand as a viscous oil with [a]~ +62.5 ( c = 0.6. CH2Cl2). The

overall yield of (+)-1 from (-)-5 was 85 46.11

HCl (-)-5

2. The

acid. The dichloro

-

-

Scheme 2

KCN

(+)-1

An enantiomerically

diphosphine

product in CDCl3 indicated the presence of doublets

were observed

Signals due to the diastereomeric

doublets and singlets at 8 1.40, 1.75, 1.98.2.57

complex

two sets

the five strong and 2.67.9 These

salt obtained directly from the Diels-Alder

reaction. l2

complex product of (-)-2 and (-)-1 were not observed.13 As a further check,

was prepared

from the liberated

(+)-1 and the equally accessible

(+)-2. The 31P

of the crude product in CDCl3 showed two entirely new sets of doublets at 8 5 1.5 and 118.9

(3Jpp = 42.0 Hz). No resonance

signals could be detected

NMR study, the

five individual

methyl signals in the corresponding

clearly

positions

different

stereogenic

In the 3*P NMR spectrum,

at 6 52.8 and 117.3 (3Jpp = 41.9 Hz). Jn the tH NMR spectrum,

signals are identical to that recorded of the perchlorate

NMR spectrum

of (-)-5 as its chloride

ligand: the 500 MHz 1H and 3tP NMR spectra of the crude

of only one single diastereomer.

occurred as the expected

a diastereomeric

1169

ligand

purity of (+)-1 was confirmed by the quantitative repreparation

The enantiomeric

salt from (-)-2 and the liberated

methyl resonances

pure diphosphine

centres

at S 52.‘8 and 117.3. In agreement *H NMR spectrum

(6 1.40, 1.69, 1.70, 2.39, and 3.06).

in (+)-1 were formed stereospecifically

We therefore

in the presence

with the 31P

were observed

concluded

at

that the four

of (-)-2. Furthermore,

(-)-1 was

obtained in similar yield and optical purity when (+)-2 was used as the catalyst. Work is in progress in the Xray structural

determination

configurations

at the stereogenic

cycloaddition

of the various

stereoisomeric

forms

centres as well as to determine

of 5 in order to assign

the stereoelectronic

the absolute

factors that govern this

reaction.

Acknowledgement

This work was supported by the National University

of Singapore (Research Grant No

RP 920606)

References 1. 2.

and

Notes

Bosnich, B. Asymmetric Catalysis; Martinus Nijhoff: Boston, 1986; Chapt. 1. Kagan. H. B.; Sasaki, M. The Chemistry Chichester-New

of Organophosphorus

York-Brisbane-Toronto-Singapore,

Genet. J. P. Tetrahedron L&t, 1990,31,6357 3.

and references

Rahn, J. A.; Holt, M. S.; Gray, G. A.; Alcock,

Compounds;

John Wiley & Son:

1990; Chapt. 3. Juge, S.; Stephen, M,; Laffitte, J.; cited therein.

N. W.; Nelson,

J. H. Inorg.

Chem. 1989.28,

2 17

and references cited therein. 4.

Homer,

5.

Roberts,

L.; Bercz, J. P.; Bercz, C. V. Tetrahedron L&t. 1966, 5783.

6.

Vat, R.; Nelson, J. H.; Milosaljevic,

N. K.; Wild, S. B. .I. Am. Chem. Sot. 1979.101.

references 7.

4132 and

cited therein.

Allen, D. G.; McLaughlin, Chem.

6254.

E. B.; Solujic, L.; Fischer, J. Inorg. Chem. 1989.28,

1982,21,

G. M.; Robertson,

G. B.; Steffen.

W. L.; Salem, G.; Wild, S. B. Inorg.

1007.

8.

Leung P. H.; Willis, A. C.; Wild, S. B. Inorg.

9.

Key data:

(-)-3 : 3tP NMR (500 MHz, CDC13) 6 32.88 (s); IH NMR (500 MHz, CDC13) 8 2.02 (3H,

d, Chime,

3JBB = 6.4 Hz), 2.75 (3H, d. NMe, 4J pB = 1.6 Hz), 2.97 (3H, d, NMe, 4JpB = 3.5 Hz),

4.35 (lH, qn. Chime,

[a]D -70.3 ( c = 1.0, CHCl3).

3J~~ = 3JpB = 18.1 Hz,

3J~~ = 11.8 Hz, 3JpB = 39.2 Hz, 2JBB = 1.4 Hz),

ddd, PCH. 2JpB = 22.3 Hz, 3JBB = 18.1 Hz,

(18H aromatics).

1406.

3JBB = 4JpB = 6.4 Hz), 5.36 (1H. ddd, cis-PCCH,

2JBB = 1.4 Hz), 6.05 (IH, ddd. trans-PCCH. 7.13 (lH,

Chem. 1992.31,

3JB~ = 11.8 Hz),

6.60-6.90,

7.30-8.00

1170

bUNG

B.-H. Aw and P.-H.

(-)-5 : 31P NMR

(500 MHz,

NMR (500 MHz,

CDC13) 6 1.40 (3H. s, C=CMe),

(3H, d, Chime,

CDCl3)

6 52.82 (d, 3Jpp = 41.9 Hz), 117.29 (d. 3Jpp = 41.9 Hz); ‘H 1.75 (3H, s. C=CMe),

1.87 (lH,

NMe, 4Jp~ = 1.4 HZ). 2.67 (3H. dd, NMe, 4Jp~ = 4Jp~ 6.3 Hz), 6.80-8.30

(21H aromatics).

[a]D -56.3 ( c = 1.0, CHCl3).

For the diastereomeric

complex

from (+)-2 and (+)-1:

(d, 3Jpp = 42.0

118.89 (d, 3Jpp = 42.0 Hz);

Hz),

prepared

1.69 (3H, d. Chime,

(3H, d. NMe.4Jp~ H+

&,

1.98

= 3.5 Hz), 2.82 (lH, s, Hq), 3.14 (lH, ddd.

HJ, 3J~~ = 2Jp~ = 8.6 Hz, 3Jp0~ = 41.0 Hz), 3.78 (1H. m, HI), 4.45 (lH,

C=CMe),

m. &,

~JHH = 6.3 Hz), 2.38 (lH, dd, H6, cq, 2J~~ = 13.2 Hz, 3Jp~ = 24.1 Hz), 2.57 (3H. d,

3.00 (lH,

~JHH = 4Jp~ =

3tP NMR (500 MHz, CDCl3) 6 51.48 (500

MHz,

CDC13) 6 1.40 (3H, s,

~JHH = 6.1 Hz), 1.70 (3H. s. C=CMe),l.86

(lH,

m, Hg, &,

= 3.7 HZ), 2.63 (1H. dd. He, eq, 2J~~ = 14.1 Hz, 3Jp~ = 23.4 Hz),

ddd, Hb. 3J~~ = 2Jp~ = 8.0 Hz, 3Jp~

HI), 4.40 (lH,

‘H NMR

qn, CHMe,

qn, Cme,

= 37.6 Hz), 3.04 (3H, s, NMe).

3J~~ = 4JpH = 6.1 Hz), 6.70-8.10

(21H aromatics).

2.39

2.75 (lH,

s,

3.91 (lH, m,

[a]D -6.9 ( c = 0.5,

CH2Cl2). (+)-6: [oL]D +10.9 ( c = 1.0. CH2C12). The 3lP and ‘H NMR spectra

10.

the corresponding

racemic materials.3

All the complexes

were analytically

of reaction

The course carried

to that reported

for

pure.

was monito&

out by treating

are identical

by 3tP NMR spectroscopy.

(-)-3 directly

with DMPP.

However,

The cycloaddition

the reaction

reaction

could be

time was longer and the yield

was lower. 11.

The specific

rotation

uncoordinated to selected 12.

We observed

the presence product.

42.0 Hz. However,

Details

isomerism

concerning

Alder process

slowly,

presumably

instability6

of the

ligand must be recomplexed

upon liberation.

of another

it has been identified

isomer showed

due to the four different the mechanistic

(10 %) in the 3 *P NMR two sets of doublets

in subsequent

of the ortho-metallated

and the dynamic

due to the configurational

centre in (+)-I. Hence the liberated

This compound

regio-arrangement

and rrans

stereogenic

metal ions immediately

cycloaddition

different

of (+)-1 changes

phosphorus

studies as the diastereomer

naphthylamine donor

and the optically

atoms involved

aspect of this palladium(I1)

properties

spectrum

of the resulting

of the crude

at 6 29.9 and 119.9 with 3Jpp = of (-)-5 arising from pure (+)-1 (i.e. cis

in the square-planar

complex-promoted

metal chelates

complex).

asymmetric

will be published

Diels-

in a further

paper. 13.

Chooi,

S. Y. M.; Leung,

Tetrahedron:

Asymmetry

(Received in UK 14 April 1994)

P. H.; Lim, C. C.; Mok, 1992,3.

529.

K. F.; Quek,

G. H.; Sim.

K. Y.; Tan,

M. K.