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Tefnzkdmn Vol. 42, No. 16, pp. 5105 to 5109,1986 Printed in GreatBrkain.
HYDROFORMYLATION CATALYSEDBY RHODIUMCOMPLEXES OF TREHALOSE-DERIVED A HIGHLYRECIOSELECTIVEROUTE LIGANDS-aa and gg-TREDIP; TOr-METiiYLARYLPROPIONALDEHYDES (Dyson Perrins
JOHNPi. BROWNand STEPHENJ. COOK Laboratory, South Parks Road, OXFORDOX1 3QY)
RIAZ KHAN Lyle Memorial Laboratory, Tate and Lyle Research, Reading) (Receiwd in UK 13 June 1986) Rhodium complexes of the ligand cc-TREDIP give 62:l lso-regioselectivity in Abstract: the hydroformylatlon of styrene under ambiex conditions wlthou=xcess phosphine. higher The results are compared with those obtained with than any previously reported value. other ligands. and extended to the preparation of 2-(6-methoxy-2-naphthylj-propanal. a precursor of the anti-inflammatory drug naproxen. (Philip
It has been known for hydroformylation terminal
aliphatic
aldehydes;
over
fifteen
of olefins olefins
the former
years
are converted
process
in organic
scope.
a general
This may reflect
and inhibitions of
substrate
against
sufficient
behind
trans.-chelation involves
working
flexibility (bite
stages
for
selectivity.
A chelating
Hydroformylatlon
precursor 1:l
alternative CO/H, (1:l was obtained Results 20 h.
formed
if
large
gas,
quantities
llgands
angle
with
90-120’)
and also
pathway in hydroformylation
, and with PPh, they may be mutually --cis or trans at increases
because
alleviate
with increasing
competitive
this
problem
ligation lf
phosphlne:
by CO lowers
cocomplexation
of
its
the donor
in situ.
and -BB-TREDIP. 1 and 2, with the cis chelating derived blphosphlne 4. Rather than prepare a number of
, a standard method was sought for conducting Crabtree
and Morris
have already
from the blcyclo~2,2,l~heptadlenerhodlum
this
latter
approach or 1:2)
complex may be prepared
was to react
obtained
(occasionally
the
in dichloromethane
and hydroformylation
up and analysed
has unusual
of styrene
method starting
’ since
the
molarity.
were carried
rhodium complexes
complex
base,
should
(bite
catalytic
The selectivity
monophosphines,
out with -MDIOP 3, and with the L-iditol
blphosphine
occasionally
of biphosphlne
to permit -cis-chelation
high effective
it
this,
to work with synthesis
, essential
pressure
Thus branched
are involved.
to rhodium
biphosphine
into Despite
although chemists
the
manner.’
and vinylarenes
rare’
than atmospheric
cycle.’
PPh, and other
atoms has a supficiently
is rather
catalyse
selective
significance.’
among organic
The major selective
coordinated
l
aldehydes
work has been the preparation
180’).
complexes
in a highly
commercial
synthesis
at higher
in the catalytic
rhodium ratio
Reactions
this
angle
linear
reluctance
in the backbone
two phosphines
different
into
and modest amounts of catalyst
The rationale
rhodium phosphine
conditions
is of considerable
usage of hydroformylatlon l
that
under very mild
by g.1.c.
in Table if
reaction
bisphosphlne
directly
hydroformylation the basis
cation
from (C,H,),Rh+
with an equivalent
in the presence
proceeded
are recorded up to 45 h.
ligand
provided
and an equivalent
and the phosphine.
of trls(allyl)rhodlum’
of substrate,
with a
OP one such of An
under
whereupon a deep red solution
smoothly. 1.
The reaction
was incomplete
mixture at that
was normally stage)
at 20’
stirred
for
and then worked
J. M. BROWNel al.
5106 TABLE 1
Hydroformylation
Run
Llgand
of styrene
Precursora
H&O
I Ndehydeab
Isa/n
1
2 PPh,
A
1:l
99.5
2
3
A
1:l
71
4.00
3
3
B
1:l
99
2.1c
1 43
5
4
A
1 :l
100
1 1.2
5
1
A
1 :l
70
9.4
6
1
A
2:l
90
4
17.5
7
1
B
1:l
8
1
B
2:l
9
2
A
1:l
10
2
A
2:l
11
2
B
1 :l
69
11.2
12
2
B
2:l
85
15.9
100
so’ 100
93 is0
n
-
a Precursor A IS trIa(allyl)rhodIum and precursor B is bla(bIcyalo[2,2,1]heptadlene)rhodIum In-eaohxe the precursor (0.018 -1) and tetrafluoroborate s two equivalents of NEt,. blphoaphine (0.018 ml) were dissolved in CH,Cl, (1 ml.) and degaaeed under argon. Styrene (0.44 mmol) wan added, argon replaced by CO/Hz and uptake of gas monitored by burette. The reaotlon mixture !a8 passed through a short column of silica gel and analyaed dlreatly by g.1.c :3% Carbouax, 120 1. Recovered starting material and reduced product were not distinguished in this analysis. C Single runs, otherwise experiments conducted at least In duplioate. The moat interesting
feature
of these
obeerved
with -oa TREDIP 1 and precursor literature. In WflkInaon’a early work, selectivity
of
8:l
in
gave aelectivitiea phosphine.’
Other cases Include
CHIRAPHOScomplexes,** ratio
of
towards groups ratio
12.9:1
for
both
the rate
that
to employ a substantial
high selectivity
of
observed
the reactivity
of
of the backbone
indioates
energy
barrier.
that This
case
oxygen-coordination
interoonversion
that
may remain bound to rhodium throughout
of affairs
the catalytic
styrenes
some special
may be -018 or The inherent should
for
cycle,
a
electron-withdrawing that
the ligand
Is possible.”
state
and
being E-NO, with an e:n
between the two geometries
is a very favourable
of isomer
catalyst,
of E-substituted
1 a suggests
of
up to lO:l,
of Wilklnaona
I* the beat.oaae
In the case
It has been shown that rhodium complexes and In the latter
giving
analogues
It was demonstrated
monophoaphlnea
exoeaa(>4:1)
of the branohed-chain
of dibenz.ophoaphole,*”
by HRh(PPh,),
In the
lao/n
work with chiral
In favour
polymer-supported
reported
HRhCO(PPh,), effected
Subsequent
and the regloaeleotIvIty,
trana-chelated.
high regioaeleotIvIty
than any case
of atyrene.’
In a comparison
catalyaed
The high selectivity
may be Involved.
the chelate
Yith
more selective
use necessary
derivatives
16:l.
was achieved.”
increased
intrinsic
which it
chelating
Is the reproducibly
being
was reported
where a reasonably
giving
hydroformylatlon
of 25:l.
it
the hydroformylatlon
up to 49:l
has been recorded
experiments
B, this
oocur
flexIbllIty with a low
hydroformylatlon
as Indicated
feature
since
in Figure
1.
The -66 Isomer 2 favours -cls-coordination w)re and trana-coordination rather less than does the wa-isomer 1, and it is notably leas affeotlve aa a regioaeleotive hydroformylation catalyst. The hydroformylatlon effort
haa been devoted
moderate.“’ 75%)‘.
PtCl,
purity
complexes
but the reaction
branched-chain of
vaniahingly
isomer
product small,
of atyrene
to P-phenylpropanal
to asymmetric
in the presence
of SnCl,
must be run at high pressure and over
was examined
hydrogenation, by N.m.r.
as might be expected
is
chiral for
introduces
a new chiral
With rhodium aomplexea’the
oatalyala.
give
a ligand
enantiomer
and the selectivity,
rather
shift
much better
weak.
analysis
centre,
results
and much
are uniformly
exoeaaes
both towards
(up to
the
In the present
case
using
and shown to be
Eu(hfc),
with a high degree
of baokbone
the optical flexIbIlIty.
Hydroformylationcalalyscdby rhodiumcomplexes
Figure 1 A hydroiormylatlon route to Naproxen 2-Arylproplonlc clinlcally
acids ere an Important clans of antIInfl.ammatory agente,l’
viable drugs Buren 5, Roben 6. Suproren 7 and Naproxen 8.
hydroiormylation by ao-lWDIP rhodium complexes wae examined by application enalcgue
.
cross-coupling
0r
eelective
to a Naproxen
Present routes to the oompound involve straightrorward aratlc
nickel-oatalyeed
Including the
The generality chemistry”
between 2-(bromomegneslo)-6wthoxynaphthalene
or
and the cssgne8Ium
salt oi ethyl P-bromoproplonate.”
&O””
yaw (qJOOH c”o$&oo”
5
6
O
Synthesis or 6-ethenyl-2-methoxynaphthalene brcvalde with 2-Iodo-6-wthoxynaphthalene
3
7
8
9 was eireoted by oross-aoupllng
In the presenoe oi a catalytic
vinylmagnesium
amount oi Pd(PPh,),*’
uhloh
gave the desired product in 691 yield.
Hydroiornylatlon wax.carried out according to procedure A,
end gave a mixture ol the two aldehydes
10 and 11 in
the oatalyst
Is optloally
active,
the reaction
ratio 20:1,
basis or Its ‘H N.m.r. spectrum In the presence or Eu(hic),. naproxen esters using the lipase
,,,p
3
9
10
11
0r
been reported.”
04” $x+0 3
Although
raoemic, judged on the
hzylPat.10 resolution
rrcm Candida oyllndracea has reoently
--”
3
In 94.51 Isolated yield.
product 10 is eiieotlvely
racemlo
J. M. BROWN er al.
5108 Two
further results
act-l-one,
should be reoorded. Firstly the seleotivlty in hydroformylation ot where n-nonanal predominates, is Lowry when o(r-TREDIPis employed in proaedure A. slnue
28% of the branched-chain Isomer was observed, compared with around 101 when PPh,-based catalysts are used.&
Purther the hydroformylatlon of phenyl vinyl sulphoxide gives 971 of the branched-ohaln
aldehyde 12 with E-TREDIP as catalyst.
One dlastereomer appears to predominate In the ‘H N.a.r.
spectrum of crude prodwt but this may refleot rather ,acIdic.
and faollltate
keto
thermodynamio control since the g-proton will
en01 Interoonverslon.
The reaction
is very slcu,
be
however,
and only a few turnovers were achieved in 48 h. under ambient conditions. Aoknowledgment We thank SERCfor a and Johnson-Matthey p.1.0.
CASE
studentship (to SJC In collaboration
with Tate and Lyle)
for the loan of rhodium salts.
Experlwntal Trls(allyl)rhodiumr’ tetrafluoroborate” and -bls(bIcyolo[2,2,1~heptadIene)rhodium tetrak18(tr1pheny1phoaph1ne)pa11ad1um1’ were prepared by published proaedurea. All reactions Involving organometalllc
complexes were conducted under an inert atmosphere using vaouumline
and Suhlenk techniques as previously desorlbed. 2-Iodo-6-methoxynaphthalene 2-Methyl-2-propylllthlum in pentane (1.4 M, 70 ml, 98 mm011was added to a solution of 2-braao-6-methoxynaphthalene*’ (10.01 g, 42.2 -1) in tetrahydrofuran (90 ml) at -78’. The mixture was stirred at -78’ for lh, a solution of Iodine (16.85 g, 66.4 mmol) In tetrahydrofuran (7Ou1l) was added, and the mixture was then stirred at room tslaperature for 72h. The solvent was re moved in vaouo, dlohloromethane (250 ml) was added and the solution was washed with water (100 ml-saturated sodium thiosulphate solution (4 x 100 ml), water (100 ml) and saturated sodium chloride solution (100 ml) and then dried (anhydrous magneslu sulphate). Ttm solvent was rwved in vacua and the residue recrystallized from dlchloromathane/methanol to give 2-lodod-osthoxym.p. 143-4@1 ‘H-N.m.r.r 6 (300 MHz. (10.03 gm. 35.3 llrmol, 83.7%) as yellow plates; (3H, a, One), 7.05-7.7 (5H, m, arom), 8.15 (lH, m, arm, ortho-H); found: C, 46.50; H, 3.28: C,,H,IO requires: C, 46.50; H, 3.191. 6-Ethenyl-2-methoxynaphthalene Tetrakis(trIphenylphosphIne)palladlum (0) (171) (0.100 g, 0.087 mwl) was added to a mixture of 2-iodo-6-methoxynaphthalene (0.99 g, 3.48 msorln tetrahydrofuran (15 ml) and vinylmagneslllm bromide (0.8 Fl, 12 ml, 9.6 mm011In tetrahydrofuran at -78’. The solution was stlrrod under argon at room temperature for 5d, during which time It beoame brown and a white precipitate was formed. Hydrochlorlo aold (3 M, 4 ml, 12 mm011was added, the solvent was removed in vacua, dlchloroplethane [!j; ml; and water (50 ml) were added, and the aqueous layer wss extraoted with dlohloromsthane . The combined organic layers were washed with saturated sodium hydrogen oarbonate solution (50 ml), water (2 x 50 ml) and saturated sodium chloride solution. The solution was dried (anhydrous ma$esIum 8ulphat.e) and the solvent removed In vacua to give an orange residue whloh was sublimed (100 1 as a white solid, examination of whloh by ‘H-NW showed a mixture of 6-ethenyl-2-methoxynaphthalene (881) and 2-methoxynaphthalene (121). Reorystalllzation from m.p. 92-3. ethanol/water gave pure 6-ethenyl-2-methoxynaph thalene (0.440 g, 2.39 mreol, 68.65); (lit.“@ 93-4*1: ‘H-NMr 6 (300 MHz, CDCl,) 3.95 (3H, 8, OrCe), 5.3 (1H. d, J 10.5 Hz. -C&,Hg). 5.85 (lH, d, J 17 Hz. -CH H 1, 6.85 (lH, dd, Jm 10.5 Hz, Jm 17 Hz, CaHg), 7.15 (2H, m, arod, 7.6-7.75 (4H, m, arom A-f. 2*(2-methoxy-6-naphthylFpropana1 6-Ethenyl-2-methoxynaphthalene (166) (100 mg. 0.543 -1) was added to a degassed aolutlon of the blphosphlne aa-TREDIP (28 mg, O.Ormmol) and trls(allyl)rhodlum (8 mg, 0.035 !maoi) in hydrogen/carbon monoxide (1:l ratio) for dichloromethane T? ml). The solution was stirred ar The solvent was 48h.. and then passed through a column of silica gel to remove the rhodium salts. removed In vacua and examination of the crude product (‘H-NW Indicated the presence of 21(2-met~aphthyl)-propanal (951) and 3-(6-methoxy-2-naphthyl-propanal (5%). There was no Subllmatlon of the product gave a white solid (110 mg, 0.513 -1, traoe of starting material. 94.51). showing the same ratio of aldehydic products of 95:5; mainly 2’(2-mathoxy-6-naphthyl) ‘H-W d (300 MHz, CDCl,) 1.55 (3H, d, J 7 Hz. CH,). 3.8 (1H. q. J 6 Hz, CH), 3.95 (3H, 7.15 (2H m, Ar), 7.3 (2H, m, ArLr),7.75 (2H, m, Ar). 9.75 (lH, d, J 1 Hz, CHO); m.P. (llt ,.’ 52-7’ ).
Hydrofonnylation catalyxai by rhodium complexes
5109
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