Water-soluble group 8 and 9 transition metal complexes containing a trihydrazinophosphaadamantane ligand: Catalytic applications in isomerization of allylic alcohols and cycloisomerization of (Z)-enynols in aqueous medium

Article abstract of DOI:10.1002/adsc.200606115

An optimized synthesis of the 2,4,10-trimethyl-1,2,4,5,7,10-hexaaza-3- phosphatricyclo-[3.3.1.1^3,7]decane ligand (THPA) is described. It readily reacts with the dimers [{RuCl(μ-Cl)(η⁶-arene)} ₂] and [[MCl(μ-Cl)(cod)}₂] to yield the corresponding mononuclear complexes [RuCl₂(THPA)-(η⁶-arene)] [arene = C₆H₆ (4a), p-cymene (4b), 1,3,5-C₆H ₃Me₃ (4c), C₆Me₆ (4d)] and [MCl(THPA)(cod)] [M = Rh (7a), Ir (7b)], respectively. Treatment of 4a and b with MeOTf affords the cationic derivatives [RuCl₂(THPA-Me) (η⁶-arene)][OTf] {arene = C₆H₆ (5a), p-cymene (5b); THPA-Me = 1,2,4,10-tetramethyl-2,4,5,7,10-pentaaza-1-azonia-3- phosphatricyclo-[3.3.1.1^3,7]decane}. The arene-ruthenium(II) complexes 4a-d and 5a and b are efficient catalysts for the redox isomerization of allylic alcohols into carbonyl compounds in both THF and aqueous media. The catalytic systems can be recycled by a simple extraction process and used in up to 4 consecutive runs. All the water-soluble complexes prepared in this work are able to promote the cycloisomerization of (Z)-enynols to afford furans in water, the best performance being obtained with the iridium catalyst 7b. Furthermore, 7b has shown an excellent recyclability (10 runs). This study represents the first example of iridium-catalyzed cycloisomerization of (Z)-enynols.

Full text of DOI:10.1002/adsc.200606115

FULL PAPERS
DOI: 10.1002/adsc.200606115
Water-Soluble Group 8 and 9 Transition Metal Complexes
Containing a Trihydrazinophosphaadamantane Ligand: Catalytic
Applications in Isomerization of Allylic Alcohols and
Cycloisomerization of (Z)-Enynols in Aqueous Medium
Alba E. Díaz-lvarez,a Pascale Crochet,a,* Maria Zablocka,b,* Carine Duhayon,c
c,
Victorio Cadierno,a JosØ Gimeno,a andJean Pierre Majoral *
a
Departamento de Química Orgµnica e Inorgµnica, Instituto Universitario de Química Organometµlica “Enrique Moles”
(Unidad Asociada al CSIC), Facultad de Química, Universidad de Oviedo, 33071 Oviedo, Spain
Fax : (+34)-985-10-3446; e-mail: pascale@fq.uniovi.es
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90363 Lodz, Poland
b
Fax : (+48)-426-84-7126; e-mail: zabloc@bilbo.cbmm.lodz.pl
Laboratoire de Chimie de Coordination, CNRS, 205 route de Narbonne, 31077 Toulouse, France
c
Fax : (+33)-561-55-30-03; e-mail: majoral@lcc-toulouse.fr
Received: March 17, 2006; Accepted: June 20, 2006
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.
Abstract: An optimizedsynthesis of the 2,4,10-tri-
the redox isomerization of allylic alcohols into car-
bonyl compounds in both THF and aqueous media.
methyl-1,2,4,5,7,10-hexaaza-3-phosphatricyclo-
[3.3.1.13,7]decane ligand (THPA) is described. It The catalytic systems can be recycledby a simple ex-
readily reacts with the dimers [{RuCl
arene)}2] and[{MCl (m-Cl)(cod)}2] to yieldthe corre-
sponding mononuclear complexes [RuCl2(THPA)- this work are able to promote the cycloisomerization
(h6-arene)] [arene=C6H6 (4a), p-cymene (4b), 1,3,5- of (Z)-enynols to affordfurans in water, the best per-
C6H3Me3 (4c), C6Me6 (4d)] and[MCl (THPA)(cod)] formance being obtainedwith the iriidum catalyst
A
ACHTREUNG
A
ACHTREUNG
AHCTREUNG
ACHTREUNG
A
ACHTREUNG
[M=Rh (7a), Ir (7b)], respectively. Treatment of 4a 7b. Furthermore, 7b has shown an excellent recycla-
and b with MeOTf affords the cationic derivatives bility (10 runs). This study represents the first exam-
[RuCl
A
(h6-arene)]
A
{arene=C6H6 ple of iridium-catalyzed cycloisomerization of (Z)-
(5a), p-cymene (5b); THPA-Me=1,2,4,10-tetrameth- enynols.
yl-2,4,5,7,10-pentaaza-1-azonia-3-phosphatricyclo-
[3.3.1.13,7]decane}. The arene-ruthenium(II) com- Keywords: allylic alcohols; enynols; isomerization; P
plexes 4a–d and 5a and b are efficient catalysts for donor ligands; ruthenium; water-soluble
Introduction
lytic cycles, minimizing the overall cost of the process-
es. With the aim to develop new catalytic systems
active in water, the syntheses of a great variety of
Aqueous organometallic chemistry has receiveda
great deal of attention in recent years due to the water-soluble ligands, especially phosphanes, have
many advantages that an aqueous medium presents been reported.[3] Nevertheless, the catalytic applica-
[1]
for both stoichiometric andcatalytic processes.
The tions of most of these ligands remain limited, with the
main interest in using water as solvent stems from its exception of aryl-sulfonatedphosphines (e.g.,
abundance, low cost and non-toxic nature, all these TPPMS, TPPTS, TPPDS) which have been extensive-
characteristics fulfilling the green chemistryꢀs princi- ly studied in catalysis.[1,3] Recently, the cage-like
ples.[2] In addition, its immiscibility with many organic water-soluble phosphine 1,3,5-triaza-7-phosphaada-
compounds allows the easy separation of the reaction mantane[4] (PTA) has receivedan increasing attention
products from the water-soluble catalyst by simple de- anda variety of ruthenium andrhodium PTA-com-
cantation or extraction processes. Moreover, the cata- plexes have appearedto be promising catalysts in
lyst solution recoveredcan be re-usedin further cata-
aqueous media.[5] In this context, some of us reported
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Alba E. Díaz-lvarez et al.
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in 1982 the synthesis of the closely relatedtrihydrazi-
(Scheme 1), in this case only 15 h are required.[6c]
nophosphaadamantane ligand THPA (2 in Scheme 1) This methodgives 2 as an air-stable white powder in
by desulfuration of the readily available thiophos- 80% yield.
phane 1.[6] Surprisingly, despite its great potential, the
Treatment of dimers [{RuCl
coordination chemistry of this water-soluble ligand [arene=C6H6 (3a),[9] p-cymene (3b),[10] 1,3,5-
has been completely neglected, [Fe(CO)
4(THPA)] C6H3Me3 (3c),[9] C6Me6 (3d)[10]] with a two-fold
(m-Cl)
(h6-arene)}2]
AHCTREUNG
being the only transition-metal complex reportedtill
excess of the THPA ligand 2 affords the correspond-
ing mononuclear complexes [RuCl2(THPA)
now in the literature.[7]
A
ACHTREUNG
arene)] [arene=C6H6 (4a), p-cymene (4b), 1,3,5-
C6H3Me3 (4c), C6Me6 (4d)], isolatedas air-stable
orange solids in 73–85% yield, via the expectedcleav-
age of the chloride bridges (Scheme 2). Analytical
Scheme 1. Synthesis of the THPA ligand 2.
With all these precedents in mind and stimulated
by the increasing demand for novel, efficient water-
soluble catalysts, we decided to explore the coordina-
tion chemistry andthe catalytic applications of the
THPA ligand, starting from an optimized synthesis of
THPA as well as the preparation of the first rutheni-
um, rhodium and iridium complexes containing this P
donor ligand. They have proved to be soluble in or-
ganic solvents andin water, andhave been successful-
ly usedto promote the catalytic isomerization of allyl-
ic alcohols into carbonyl compounds in both THF and
aqueous media. They are also active catalysts in the
cycloisomerization of (Z)-enynols into furans in aque-
ous media. Since only one water-soluble catalyst has
[8]
been reportedto date,
they provide new opportuni-
Scheme 2. Synthesis of the ruthenium complexes 4a–d and
5a, b.
ties to perform this transformation in water.
Results and Discussion
andspectroscopic data confirm the proposedformula-
tion (see Supporting Information). In particular, the P
coordination of the ligand to ruthenium is clearly as-
sessedin the 31P{1H} NMR spectra by a downfield
shift of the phosphorus resonance with respect to the
free ligand[ d=123.4 (4a), 128.1 (4b), 126.4 (4c),
Synthesis of THPA and its Water-Soluble Complexes
As commentedabove, the trihyrdazinophosphaaad-
mantane ligandTHPA ( 2) can be easily obtainedby
desulfuration of the thiophosphane 4,6,9-trimethyl-5- 126.7 (4d) vs. 101.8 (2)]. In addition, the structure of
thio-1,3,4,6,7,9-hexaaza-5-phosphatricyclo[3.3.1.13,7]-
4b has been unambiguously confirmedby a single
decane (1), which is readily accessible in a multigram- crystal X-ray diffraction study (Figure 1). The mole-
scale through the reaction of S=PCl3 with methylhy- cule displays the characteristic pseudooctahedral
drazine and further treatment with formaldehyde. “three-leggedpiano-stool” geometry, the observed
Nevertheless, in our original preparation of 2 the de- bonddistances andangles aroundthe metal compar-
sulfuration process requiredthe use of a large excess
of tri-n-butylphosphane, which acts both as reducing [RuCl
agent andsolvent, as well as an extremely long reac-
tion time (15 days), making the synthesis rather tedi-
ous.[6b] Fortunately, we recently foundthat this reduc-
ing well to those foundin the relatedPTA derivatives
2(PTA)(h6-p-cymene)][11] and[RuCl (h6-
2(PTA)
C6H6)].[12]
It is well-known that the N-protonatedor alkylated
forms of PTA can also act as ligands, the affinity for
A
G
ACHTREUNG
tion step can be considerably shortened by treating 1 water of the resulting cationic complexes being en-
with Raney nickel in acetonitrile at room temperature hancedwhen comparedto that of the neutral counter-
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Adv. Synth. Catal. 2006, 348, 1671 – 1679

Transition Metal Complexes Containing a Trihydrazinophosphaadamantane Ligand
FULL PAPERS
the ligandframework remaining almost unchanged
when comparedto those foundin the neutral complex
4b.[14]
The coordination chemistry of the THPA ligand
has been extended to Group 9 metals. Thus, the mon-
onuclear derivatives [RhCl
[IrCl(THPA)(cod)] (7b), couldbe readily synthesized
(68–86% isolatedyields) from the reactions of 2 with
the dimeric precursors [{RhCl(m-Cl)
(cod)}2][15] (6a)
and[{IrCl (m-Cl) (6b), respectively
(cod)}2][16]
A
G
A
ACHTREUNG
A
ACHTREUNG
A
ACHTREUNG
(Scheme 3). The formation of the neutral iridium
Figure 1. ORTEP-type view of the structure of [RuCl2
(THPA)(h6-p-cymene)] (4b). Hydrogen atoms are omitted
ACHTREUNG
À
for clarity. Selectedbondlengths (Š) andangles (deg): Ru
Cl(1)=2.4121(19); Ru Cl(2)=2.4110(17); Ru P=2.294(2);
À
À
Scheme 3. Synthesis of the rhodium and iridium complexes
7a, b.
À
À
À
À
À
Cl(1) Ru Cl(2)=88.03(7); Cl(1) Ru P=89.70(7); Cl(2)
À
À
À
Ru P=88.14(7); P N(average) =1.706 (Æ0.01); N N(average)
=
À
À
N
1.432
(Æ0.01);
N CH2(average) =1.475
(Æ0.01);
CH3(average) =1.474 (Æ0.01).
complex 7b is noteworthy since it has been reported
that, under similar reaction conditions, dimer 6b
reacts with the relatedPTA ligandto affordthe cat-
parts.[5] In this context, we have foundthat treatment
of [RuCl2(THPA)
A
(h6-arene)] [arene=C6H6 (4a), p- ionic derivative [Ir
A
N
cymene (4b)] with a large excess of methyl triflate Compounds 7a, b have been characterizedby means
leads to the high-yield formation (70–89%) of the cat- of elemental analyses, multinuclear NMR spectrosco-
ionic
[OTf][13] [arene=C6H6 (5a), p-cymene (5b)], as the and, in the case of the rhodium complex 7a, by single-
result of the selective methylation of one of the crystal X-ray diffraction methods (see Figure 3).
bridgehead nitrogen atoms of the tricyclic ligand skel- All the complexes preparedin this work are soluble
complexes
[RuCl
2(THPA-Me)
G
ACHTREUNG
eton (Scheme 2). The structure of 5a has been un- in common organic solvents (CH2Cl2, acetone, etc)
equivocally confirmed by an X-ray diffraction study and, as expected, are also soluble in water, making
(see Figure 2), the main structural parameters within
Figure 2. ORTEP-type view of the structure of the cation
[RuCl2
N
N
omittedfor clarity. Selectedbondlengths (Š) andangles
(deg): Ru Cl(1)=2.4025(18); Ru Cl(2)=2.4005(19); Ru
Figure 3. ORTEP-type view of the structure of [RhCl-
(THPA)(cod)] (7a). Hydrogen atoms are omitted for clarity.
Selectedbondlengths (Š) andangles (edg): Rh
À
À
À
G
ACHTREUNG
À
À
À
À
À
P=2.2791(18); Cl(1) Ru Cl(2)=87.83(7); Cl(1) Ru P=
Cl=
À
À
À
À
À
À
À
87.52(6); Cl(2) Ru P=89.39(6); P N(average) =1.701 (Æ
2.3716(14); Rh P=2.2489(13); P Rh Cl=95.25(5);
P
À
À
À
À
0.04); N N(average) =1.472 (Æ0.02); N CH2(average) =1.481 (Æ
N
(average) =1.696 (Æ0.01); N N(average) =1.463 (Æ0.02); N
À
À
CH2(average) =1.475 (Æ0.01); N CH3(average) =1.461 (Æ0.01).
0.05); N CH3(average) =1.459 (Æ0.03).
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Alba E. Díaz-lvarez et al.
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them suitable for catalytic studies both in organic and the reaction was monitoredby GC analyses. Under
aqueous media.[18]
these conditions, 4a–d showedvery high activities, the
conversion being in all cases complete after only
5 min (entries 1–4; TOF=1200 hÀ1). In contrast, the
neutral rhodium and iridium derivatives (7a, b) are,
under the same reaction conditions, much less effi-
cient (entries 5 and6) requiring 17 and2.5 h, respec-
tively, to reach similar yields. Remarkably, at a lower
Isomerization of Allylic Alcohols into Ketones in
Organic and Aqueous Media
The isomerization of allylic alcohols promotedby
transition metal complexes represents a straightfor- catalyst loading (0.2 mol%), the results obtained
wardsynthetic route to the corresponding saturated
using the ruthenium complexes 4a–d are strongly de-
carbonyl compounds (Scheme 4).[19] This process, pendent on the arene ligand. Thus, while the benzene
and p-cymene derivatives (4a, b) remain very efficient
(entries 7–8 in Table 1), a slow reaction or an incom-
plete conversion have been observedfor the mesity-
lene (4c) andhexamethylbenzene complexes (4d), re-
[23]
spectively (entries 9 and10).
Scheme 4. Catalytic isomerization of allylic alcohols.
The most active catalysts, namely the ruthenium
complexes 4a and 4b, have also been successfully em-
which proceeds with a total atom economy, can be ployedin the isomerization of 1-hepten-3-ol (R =n-
[19]
catalyzedby Group 8, 9 and10 metal derivatives,
andin particular by cyclopentadienyl-ruthenium com-
Bu), 1-hexen-3-ol (R=n-Pr), 1-penten-3-ol (R=Et)
and a-vinylbenzyl alcohol (R=Ph) into the corre-
plexes,[20] some of which are extremely effi- sponding carbonyl compounds (Table 2). Notably, the
cient.[20b,d,e] Despite the great interest in the catalytic
isomerization of allylic alcohols in synthesis, efforts to
develop such a reaction in aqueous medium are still
scarce.[21,22] In the context of our ongoing interest in
studying this synthetically useful transformation in
aqueous media,[21d–g] we have exploredthe catalytic
activity of the THPA-basedcomplexes.
First, the catalytic activity of the neutral arene-ruth-
enium(ii) complexes 4a–d has been checkedin the
isomerization of 1-octen-3-ol into octan-3-one using
THF as solvent (Table 1). In a typical experiment,
4 mmol of substrate, 1 mol% of catalyst, 5 mol% of
KO-t-Bu and20 mL of THF were heatedat 75 8C and
Table 2. Isomerization of various allylic alcohols catalyzed
by 4a, b in THF.[a]
Substrate
Catalyst mol% Time Yield
TOF
Ru
[%]
[hÀ1][b]
1-hepten-3-ol
1-hepten-3-ol
1-hexen-3-ol
1-hexen-3-ol
1-penten-3-ol
1-penten-3-ol
a-vinylbenzyl
alcohol
4a
4b
4a
4b
4a
4b
4a
0.2
0.2
0.2
0.2
0.2
0.2
1
1.5 h 100
1.33 h 100
1.25 h 100
333
375
400
495
333
300
1200
1 h
100
1.5 h 100
1.67 h 100
5 min 100
a-vinylbenzyl
alcohol
4b
1
5 min 100
1200
Table 1. Comparison of the different THPA-based catalysts
in the isomerization of 1-octen-3-ol into octan-3-one in
THF.[a]
[a]
Reactions carriedout at 75 8C using 4 mmol of the corre-
sponding allylic alcohol, 20 mL of THF, the catalysts and
KO-t-Bu (Base/Ru ratio=5).
[b]
Entry Catalyst mol%
Metal
Time Yield
[%]
TOF
Turnover frequency [(mol product/mol Ru)/time] were
calculatedat the time indicatedin each case.
[hÀ1][b]
1
2
3
4
5
6
7
8
9
4a
4b
4c
4d
7a
7b
4a
4b
4c
4d
1
1
1
1
1
1
0.2
0.2
0.2
0.2
5 min 100
5 min 100
5 min 100
5 min 100
1200
1200
1200
1200
6
quantitative conversion of a-vinylbenzyl alcohol into
propiophenone can be achievedin only 5 min using a
catalyst loading of 1 mol% (TOF=1200 hÀ1). This
17 h
2.5 h
99
99
[19]
result is one of the best reportedfor this substrate.
40
Taking advantage of the hydro-solubility of our
THPA-basedcatalysts, we exteneddthe catalytic
study to an aqueous medium. Firstly, we checked the
catalytic activities of the neutral ruthenium complexes
4a–d in the isomerization of 1-octen-3-ol into octan-3-
one using water as solvent (Table 3). In order to com-
pare the results with those obtainedin THF, the ex-
periments were carriedout under the same experi-
mental conditions, i.e., at 758C using 4 mmol of sub-
15 min 100
30 min 100
1.25 h 100
2000
1000
400
23
10
3 h
14
[a]
Reactions carriedout at 75 8C using 4 mmol of 1-octen-3-
ol, 20 mL of THF, the catalyst andKO- t-Bu (base/cata-
lyst ratio=5).
Turnover frequency ((mol product/mol catalyst)/time)
was calculatedat the time indicatedin each case.
[b]
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Transition Metal Complexes Containing a Trihydrazinophosphaadamantane Ligand
FULL PAPERS
Table 3. Isomerization of 1-octen-3-ol into octan-3-one in water
using the THPA-basedRu catalysts.
water vs. THF which favors the dissociation of the
[a]
[25]
À
Ru Cl bondin complexes 4 and 5.
Nevertheless, in
the presence of base better catalytic efficiencies are
observed. The most active catalysts, i.e., 4a, b and 5a,
b, have also been checkedin the isomerization of 1-
hepten-3-ol, 1-hexen-3-ol, 1-penten-3-ol and a-vinyl-
benzyl alcohol in water (Table 4). In all the cases
almost quantitative conversions were observedafter
only 0.75–3.5 h, pointing out the generality of this cat-
alytic transformation in aqueous media.
The catalyst recycling has also been investigated
using the isomerization of the 1-octen-3-ol into octan-
3-one as a model reaction. Thus, we have found that,
after a simple extraction process with hexane anddi-
ethyl ether (details are given in the Experimental Sec-
tion), the catalysts 4a–b and 5a–b can be re-usedin 2–
4 subsequent cycles (see Table 5). The best results
were obtainedusing the cationic complex 5a which, in
Entry Catalyst With KO-t-Bu[b]
Yield Time TOF[c] Yield Time TOF[c]
Without KO-t-Bu
[%]
[%]
1
2
3
4
5
6
4a
4b
4c
4d
5a
5b
99
99
99
100
99
99
45 min 132
100
100
98
71
13
1 h
1.25 h 80
3.5 h 28
9 h
6 h
5 h
100
1 h
2 h
3.5 h
1 h
99
50
29
99
8
2
19
30 min 200
96
[a]
Reactions carriedout using 4 mmol of 1-octen-3-ol, 20 mL
of water, 1 mol% of catalyst.
[b]
[c]
With 5 mol% of KO-t-Bu.
Turnover frequency [(mol product/mol Ru)/time], in hÀ1,
was calculatedat the time indicatedin each case.
strate, 1 mol% of ruthenium, 5 mol% of KO-t-Bu the fourth run, is still able to isomerize quantitatively
[24]
and20 mL of water.
Thus, as previously observed 1-octen-3-ol into octan-3-one within 7 h.
in THF, the reaction rates were foundto be strongly
dependent on the nature of the arene ligand, follow-
ing the order: C6H6 (TOF=132 hÀ1)>p-cymene Cycloisomerization of (Z)-Enynols into Furans in
(TOF=99 hÀ1)>mesitylene (TOF=50 hÀ1)>hexa- Aqueous Media
methylbenzene (TOF=29 hÀ1) (entries 1–4). Under
the same conditions, the cationic ruthenium com- The synthesis of furans is of particular interest since
plexes 5a, b are also active showing similar catalytic they can be foundin many naturally occurring com-
performances as those of their neutral counterparts pounds being also key structural units in several im-
4a, b (entries 5 and6 vs. 1 and2 in Table 3). It is in-
teresting to note that both the neutral (4a–d) andcat-
ionic (5a, b) complexes remain able to promote the andversatile building blocks in organic synthesis.
portant pharmaceuticals as well as in flavor andfra-
grance compounds.[26] Furthermore, furans are useful
[27]
isomerization of allylic alcohols in the absence of One of the most attractive synthetic routes for func-
base, in contrast with that observedin THF. This fact
can be attributedin part to the higher polarity of
tionalizedfuran derivatives is basedon the transition-
metal-catalyzedcycloisomerization of ( Z)-2-en-4-yn-
Table 4. Isomerization of various allylic alcohols catalyzedby 4a, b and 5a, b in water.[a]
À1 [b]
Substrate
Catalyst
mol% Ru
Time
Yield[%]
TOF [h
]
1-hepten-3-ol
1-hepten-3-ol
1-hepten-3-ol
1-hepten-3-ol
1-hexen-3-ol
1-hexen-3-ol
1-hexen-3-ol
1-hexen-3-ol
1-penten-3-ol
1-penten-3-ol
1-penten-3-ol
1-penten-3-ol
a-vinylbenzyl alcohol
a-vinylbenzyl alcohol
a-vinylbenzyl alcohol
a-vinylbenzyl alcohol
4a
4b
5a
5b
4a
4b
5a
5b
4a
4b
5a
5b
4a
4b
5a
5b
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
1 h
98
99
95
99
96
98
99
96
99
96
97
100
95
99
97
99
98
66
63
132
48
39
85
64
132
38
65
26
19
50
129
50
1.5 h
1.5 h
45 min
2 h
2.5 h
1.17 h
1.5 h
45 min
2.5 h
1.5 h
3.5 h
2.5 h
2 h
45 min
2 h
[a]
Reactions carriedout at 75 8C using 4 mmol of the corresponding allylic alcohol, 20 mL of H2O, the catalysts andKO- t-
Bu (Base/Ru ratio=5).
Turnover frequency [(mol product/mol Ru)/time] was calculated at the time indicated in each case.
[b]
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1675

Alba E. Díaz-lvarez et al.
Table 6. Cycloisomerization of (Z)-enynols.[a]
FULL PAPERS
Table 5. Recycling of the catalysts 4a, b and 5a, b in the iso-
merization of 1-octen-3-ol into octan-3-one.[a]
R
Catalyst
Time
Yield[%]
Catalyst
Cycle
Time
Yield[%]
H
H
H
H
H
H
H
H
4a
4b
4c
4d
5a
5b
7a
7b
7b
7b
7b
7b
7b
5 h
5 h
5 h
5 h
5 h
6 h
6 h
1 h
30 min
30 min
30 min
1 h
78
93
92
77
98
92
51
96
99
99
99
99
81
4a
1
2
3
1
2
3
4
5
1
2
3
1
2
3
45 min
3 h
4 h
99
99
4
5a
1 h
99
99
99
99
32
99
99
83
99
99
95
2.5 h
4.75 h
7 h
13.5 h
1 h
2 h
5 h
30 min
2 h
6 h
Et
n-Pr
4b
5b
CH2CH=CH2
CH2C(Me)=CH2
ꢀ
C CSiMe3
4.5 h
[a]
Reactions carriedout at 80 8C using 5 mmol of enynol, 1
mol% of catalyst and1 mL of H O.
2
[a]
Reactions carriedout at 75 8C using 4 mmol of 1-octen-3-
ol, 20 mL of H2O, 1 mol% of catalyst and5 mol% of
KO-t-Bu.
Table 7. Recycling of 7b in the cycloisomerization of (Z)-3-
methylpent-2-en-4-yn-1-ol.[a]
1-ols (see Scheme 5), which are readily available start-
ing materials.[28] Palladium,[29] gold[30] andespecially
Cycle
Time [h]
Yield[%]
1
2
3
4
5
6
7
8
1
1.5
2
98
96
96
96
98
97
98
92
93
96
2
2.5
2.75
2.75
3.25
3.5
4
Scheme 5. Catalytic cycloisomerisation of (Z)-enynols.
9
10
ruthenium[31] catalysts have been successfully usedto
promote such a transformation. However, only one
example has been performedin aqueous medium, the
study being limited to the commercially available
enynol (Z)-3-methylpent-2-en-4-yn-1-ol (R=H).[8]
[a]
Reactions carriedout at 80 8C using 5 mmol of (Z)-3-
methylpent-2-en-4-yn-1-ol, 1 mol% of 7b and1 mL of
H2O.
With these precedents in mind, we decided to explore formed by distillation of the 2,3-dimethylfuran under
the catalytic activity in water of our THPA-based reduced pressure, or by a biphasic extraction of the
complexes in such a cyclization process.
product with hexane (details are given in the Experi-
The catalytic cycloisomerization reactions have mental Section).
been performedat 80 8C using 5 mmol of the enynol,
1 mol% of catalyst and1 mL of water. Under these
In order to evaluate the scope of the reaction, the
cycloisomerization of (Z)-5-methylhept-4-en-6-yn-3-ol
conditions, all the complexes synthesized, i.e., 4a–d, (R=Et), (Z)-6-methyloct-5-en-7-yn-4-ol (R=n-Pr), (Z)-
5a, b and 7a, b, were foundto be able to convert ( Z)- 6-methylocta-1,5-dien-7-yn-4-ol (R=CH2CH=CH2), (Z)-
3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran 5-methyl-1-trimethylsilylhept-4-ene-1,6-diyn-3-ol (R=
ꢀ
(R=H; Scheme 5) with goodyielsd. The results,
which are summarizedin Table 6, clearly evidence the
C CSiMe3) and( Z)-2,6-dimethylocta-1,5-dien-7-yn-4-
ol [R=CH2C(Me)=CH2] catalyzedby the iridium de-
higher efficiency of the iridium derivative 7b with re- rivative 7b has been investigated(Table 6). For all
spect to its ruthenium (4a–d/5a, b) andrhodium ( 7a) these enynols, high conversions into the correspond-
counterparts, leading to a complete conversion of the ing furans are achievedin 0.5–4.5 h. These results evi-
substrate within only 1 h (96% yieldof 2,3-dimethyl-
dence the compatibility of the process with the pres-
furan; determined by GC). Moreover, catalyst 7b has ence of an additional alkene or alkyne functionality
shown an excellent recyclability allowing its use in 10 on the enynols. Only the isomerization of 5-methyl-
ꢀ
consecutive runs with only a slight decrease of the ac- hept-4-ene-1,6-diyn-3-ol (R=C CH), known to be a
tivity (Table 7). The recycling process can be per- problematic substrate,[31b] has failed.
1676
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ꢁ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2006, 348, 1671 – 1679

Transition Metal Complexes Containing a Trihydrazinophosphaadamantane Ligand
FULL PAPERS
2
3
CH2), 4.38 (d, 3H, JHH =12.4 Hz, CH2), 2.77 (d, 9H, JPH
=
=
Conclusions
15.6 Hz, NMe); 13C{1H} NMR (CDCl3): d=67.9 (d, JPC
2.8 Hz, CH2), 38.8 (d, JPC =16.8 Hz, NMe).
3
2
The syntheses of the first ruthenium, rhodium and iri-
dium complexes containing the trihydrazinophospha-
adamantane ligand THPA (2) have been described
andthe first catalytic studies are reported. All the
General Procedure for the Catalytic Isomerization of
complexes prepared, which are soluble in water as Allylic Alcohols
well as in common organic solvents, have shown a
Under an inert atmosphere, the catalyst precursor (0.2, 1 or
goodactivity in the catalytic isomerization of allylic
alcohols into the corresponding ketones both in THF
andwater, the best results being obtainedwith the
benzene and p-cymene ruthenium complexes 4a, b
2 mol%), potassium tert-butoxide (1, 5 or 10 mol%), the al-
lylic alcohol (4 mmol) and20 mL of THF or deoxygenated
water were introduced into a Schlenk tube fitted with a con-
denser. Then, the mixture was heated at 758C. The reaction
was monitoredby GC andGC/MSD, each 5 min during the
first hour andthen, the interval time was increasedprogres-
sively.
Recycling procedure: After cooling the aqueous reaction
mixture, the product was extracted twice with 20 mL of
hexane andtwice with 15 mL of diethyl ether. Then, traces
of organic solvent were eliminatedat reducedpressure. Sub-
strate (4 mmol) was added and the mixture was heated
again at the indicated temperature.
and 5a, b. Both neutral [RuCl
andcationic [RuCl 2(THPA-Me)
ruthenium complexes as well as rhodium and iridium
[MCl(THPA)(cod)] (M=Rh, Ir) (7) derivatives have
A
ACHTREUNG
A
N
ACHTREUNG
A
ACHTREUNG
shown to be efficient catalysts for the cycloisomeriza-
tion of (Z)-2-en-4-yn-1-ols providing a general syn-
thetic approach to functionalizedfurans in aqueous
media. The best performances in terms of activity and
recyclability (up to 10 cycles) have been obtained
using the iridium catalyst 7b. It is worthy of mention
that this study represents the first example of an iridi-
um-catalyzedcycloisomerization of ( Z)-2-en-4-yn-1- General Procedure for the Catalytic
ols.
In summary, we have demonstrated that the readily
Cycloisomerization of (Z)-Enynols
Under an inert atmosphere, the catalyst precursor (1
mol%), the enynol (5 mmol) and1 mL of edoxygenated
water were introduced into a sealed tube. Then, the mixture
was heatedat 80 8C andthe reaction was monitoredby GC
andGC/MSD.
Recycling procedure: After cooling the reaction mixture,
the product was distilled at reduced pressure. Substrate
(5 mmol) was added to the resulting aqueous solution and
the mixture was heatedagain at the indicatedtemperature.
The recycling can also be performedby successive extrac-
tions of the product with hexane.
available trihydrazinophosphaadamantane THPA (2)
is a suitable water-soluble ligandfor the solubilization
of transition metal catalysts in aqueous phase, repre-
senting an appealing alternative to the well-known
and widely used 1,3,5-triaza-7-phosphaadamantane
(PTA) ligand.
Experimental Section
General Remarks
Crystal Structure Determination
The manipulations were performedunder an atmosphere of
dry nitrogen using vacuum-line and standard Schlenk techni-
ques. Solvents were dried and distilled under nitrogen
before use. GC andGC/MSD measurements were made on
Crystallographic data for 4b, 5a and 7a have been deposited
with the Cambridge Crystallographic Data Centre as supple-
mentary publications Nos. CCDC 602040, 602039 and
602041, respectively. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK [Fax: (internat.) +44–1223/336–033;
E-mail: deposit@ccdc.cam.ac.uk].
TM
a Hewlett–PackardHP6890 apparatus (Supelco Beta-Dex
120 column; 30 m, 250 mm) anda Agilent 6890N instrument
coupledto a 5973 mass detector (HP-5 mS column; 30 m,
250 mm), respectively.
Synthesis of THPA (2)
Supporting Information
To a suspension of Ni-Raney (10 g) in 250 mL of acetoni-
Preparation andcharacterization of compounds 1, 4, 5 and
7. Details of X-ray diffraction analyses of 4b, 5a and 7a.
trile, S=P(NMeNCH2)3 (1) (0.75 g, 3.2 mmol) was added
A
andthe mixture stirredat room temperature overnight.
After filtration, the solution was evaporatedto dryness af-
fording a white solid which was used without further purifi-
cation. Yield: 0.52 g (80%). 31P{1H} NMR (CDCl3): d=
1
2
101.8 (s); H NMR (CDCl3): d=5.24 (d, 3H, JHH =12.4 Hz,
Adv. Synth. Catal. 2006, 348, 1671 – 1679
ꢁ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
1677

Alba E. Díaz-lvarez et al.
FULL PAPERS
[10] M. A. Bennett, T. N. Huang, T. W. Matheson, A. K.
Smith, Inorg. Synth. 1982, 21, 74.
Acknowledgements
[11] C. S. Allardyce, P. J. Dyson, D. J. Ellis, S. L. Heath,
We are indebted to the Ministerio de Ciencia y Tecnología
(MCyT) of Spain (Project BQU2003–00255) and the Gobier-
no del Principado de Asturias (Project PR-01-GE-6) for fi-
nancial support. P.C. and V.C. thank the MCyT and the Euro-
pean Social Fund for “Ramón y Cajal” contracts. M.Z.
thanks the Ministry of Science and Information Society Tech-
nologies Poland for financial support (Grant No. 3T09 A 158
29). A.E.D.A., M.Z. and J.P.M. thank the LEA (Laboratoire
EuropØen AssociØ, Toulouse-Lodz) for financial support.
Chem. Commun. 2001, 1396.
[12] H. Horvµth, G. Laurenczy, A. Kathó, J. Organomet.
Chem. 2004, 689, 1036.
[13] THPA-Me=abbreviation usedfor 1,2,4,10-tetramethyl-
2,4,5,7,10-pentaaza-1-azonia-3-phosphatricyclo-
[3.3.1.13,7]decane.
[14] The same observations have been reportedfor related
PTA-basedcomplexes: J. Kovµcs, F. Joó, A. C. BØnyei,
G. Laurenczy, Dalton Trans. 2004, 2336.
[15] A. van der Ent, A. L. Onderdelinen, Inorg. Synth. 1973,
14, 92.
References
[16] J. L. Herde, J. C. Lambert, C. V. Senoff, Inorg. Synth.
1974, 15, 18.
[1] See, for example: a) Aqueous Organometallic Chemis-
try and Catalysis, (Eds.: I. T. Horvµth, F. Joó), Kluwer,
Dordrecht, 1995; b) Aqueous-Phase Organometallic
Catalysis: Concepts and Applications, (Eds.: B. Cornils,
W. A. Herrmann), Wiley-VCH, Weinheim, 1998; c) F.
Joó, in: Aqueous Organometallic Catalysis, (Ed s.: I. T.
Horvµth, F. Joó), Kluwer, Dordrecht, 2001; d ) C. J. Li,
T. H. Chan, in: Organic Reaction in Aqueous Media,
John Wiley & Sons, New York, 1997; e) U. M. Lind-
strçm, Chem. Rev. 2002, 102, 2751; f) C.-J. Li, Chem.
Rev. 2005, 105, 3095; g) C.-J. Li, L. Chen, Chem. Soc.
Rev. 2006, 35, 68.
[2] See, for example: a) P. T. Anastas, J. C. Warner, in:
Green Chemistry Theory and Practice, OxfordUniversi-
ty Press, Oxford, 1998; b) A. C. Matlack, in: Introduc-
tion to Green Chemistry, Marcel Dekker, New York,
2001; c) M. Lancaster, in: Handbook of Green Chemis-
try and Technology, (Eds.: J. H. Clark, D. J. Macquar-
rie), Blackwell Publishing, Abington, 2002; d) M. Lan-
caster, in: Green Chemistry: An Introductory Text, RSC
Editions, Cambridge, 2002.
[17] D. A. Krogstad, A. J. DeBoer, W. J. Ortmeier, J. W.
Rudolf, J. A. Halfen, Inorg. Chem. Commun. 2005, 8,
1141.
[18] The compounds prepared in this work present the fol-
lowing solubility in water at 258C: 2, 46.8 mgmLÀ1; 4a,
6.9 mgmLÀ1; 4b, 21.4 mgmLÀ1; 4c, 20.8 mgmLÀ1; 4d,
28.0 mgmLÀ1; 5a, 32.2 mgmLÀ1; 5b, 33.1 mgmLÀ1; 7a,
11.7 mgmLÀ1; 7b, 21.9 mgmLÀ1. For water solubility of
PTA-basedcyclopentiaednyl-ruthenium(
II)complexes
see: D. N. Akbayeva, L. Gonsalvi, W. Oberhauser, M.
Peruzzini, F. Vizza, P. Brüggeller, A. Romerosa, G.
Sava, A. Bergamo, Chem. Commun. 2003, 264.
[19] For recent reviews on the catalytic isomerization of al-
lylic alcohols see: a) R. C. van der Drift, E. Bouwman,
E. Drent, J. Organomet. Chem. 2002, 650, 1; b) R.
Uma, C. CrØvisy, R. GrØe, Chem. Rev. 2003, 103, 27.
[20] a) B. M. Trost, R. J. Kulaviec, J. Am. Chem. Soc. 1993,
117, 7809; b) C. Slugovc, E. Rüba, R. Schmid, K. Kirch-
ner, Organometallics 1999, 18, 4230; c) A. Doppiu, A.
Salzer, Eur. J. Inorg. Chem. 2004, 2244; d) M. Ito, S. Ki-
tahara, T. Ikariya, J. Am. Chem. Soc. 2005, 127, 6172;
e) B. Martín-Matute, K. Bogµr, M. Edin, F. B. Kaynak,
J.-E. Bäckvall, Chem. Eur. J. 2005, 11, 5832; f) R. C.
van der Drift, M. Gagliardo, K. Kooijman, A. L. Spek,
E. Bouwman, E. Drent, J. Organomet. Chem. 2005,
690, 1044.
[3] For reviews, see: a) P. Kalck, F. Monteil, Adv. Organo-
met. Chem. 1992, 34, 219; b) F. Joó, A. Kathó, J. Mol.
Catal. A: Chem. 1997, 116, 3; c) N. Pinault, D. W.
Bruce, Coord. Chem. Rev. 2003, 241, 1.
[4] IUPAC name: 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]-
decane.
[21] Studies performed in pure water: a) D. V. McGrath,
R. H. Grubbs, J. W. Ziller, J. Am. Chem. Soc. 1991, 113,
3611; b) T. Karlen, A. Ludi, Helv. Chim. Acta 1992, 75,
1604; c) D. V. McGrath, R. H. Grubbs, Organometallics
1994, 13, 224; d) V. Cadierno, S. E. García-Garrido, J.
Gimeno, Chem. Commun. 2004, 232; e) V. Cadierno, P.
Crochet, S. E. García-Garrido, J. Gimeno, Curr. Org.
Chem. 2006, 10, 165; f) V. Cadierno, S. E. García-Garri-
do, J. Gimeno, A. Varela-lvarez, J. A. Sordo, J. Am.
Chem. Soc. 2006, 128, 1360; g) P. Crochet, J. Díez,
M. A. Fernµndez-Zfflmel, J. Gimeno, Adv. Synth. Catal.
2006, 348, 93.
[5] A. D. Phillips, L. Gonsalvi, A. Romerosa, F. Vizza, M.
Peruzzini, Coord. Chem. Rev. 2004, 248, 955.
[6] THPA=abbreviation
usedfor
2,4,10-trimethyl-
1,2,4,5,7,10-hexaaza-3-phosphatricyclo[3.3.1.13,7]decane:
a) J. P. Majoral, R. Kraemer, J. Navech, F. Mathis, Tet-
rahedron Lett. 1975, 1484; b) J. Jaud, M. Benhammou,
J. P. Majoral, J. Navech, Z. Kristallogr. 1982, 160, 69;
c) M. Zablocka, C. Duhayon, Tetrahedron Lett. 2006,
47, 2687.
[7] M. Benhammou, R. Kraemer, H. Germa, J.-P. Majoral,
J. Navech, Phosphorus, Sulfur Relat. Elem. 1982, 14,
105.
[22] Studies performed in a biphasic system (water/organic
solvent): a) H. Bricout, E. Monflier, J. F. Carpentier, A.
Mortreux, Eur. J. Inorg. Chem. 1998, 1739; b) H Schu-
mann, V. Ravindar, L. Meltser, W. Baidossi, Y. Sasson,
J. Blum, J. Mol. Catal. A 1997, 118, 55; c) C. de Belle-
fon, S. Caravieilhes, E. G. Kuntz, C. R. Acad. Sci., Ser.
IIc: Chim. 2000, 3, 607; d) C. Bianchini, A. Meli, W.
Oberhauser, New J. Chem. 2001, 25, 11; e) D. A.
[8] The reaction, performedunedr biphasic (water/tolu-
ene) conditions, was catalyzed by an arene-rutheniu-
m(II)complex containing a water-soluble N-heterocy-
ˇ
clic carbene ligand: I. Özdemir, B. Yig it, B. C¸ etinkaya,
D. Ülkü, M. N. Tahir, C. Arıcı, J. Organomet. Chem.
2001, 633, 27.
[9] M. A. Bennett, A. K. Smith, J. Chem. Soc., Dalton
Trans. 1974, 233.
1678
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Adv. Synth. Catal. 2006, 348, 1671 – 1679

Transition Metal Complexes Containing a Trihydrazinophosphaadamantane Ligand
FULL PAPERS
Knight, T. L. Schull, Synth. Commun. 2003, 33, 827;
f) V. Cadierno, P. Crochet, S. E. García-Garrido, J.
Gimeno, Dalton Trans. 2004, 3635.
Vol. 2, (Eds: A. R. Katritzky, C. W. Rees, E. F. V. Scriv-
en), Pergamon Press, Oxford, 1996, pp. 259.
[28] This synthetic strategy has been recently highlighted:
R. C. D. Brown, Angew. Chem. Int. Ed. 2005, 44, 850.
[29] a) B. Gabriele, G. Salerno, Chem. Commun. 1997,
1083; b) B. Gabriele, G. Salerno, E. Lauria, J. Org.
Chem. 1999, 64, 7687; c) A. Jeevanandam, A. Ghule,
Y.-C. Ling, Curr. Org. Chem. 2002, 6, 841; d) B. Gabri-
ele, G. Salerno, M. Costa, Synlett 2004, 2468.
[30] a) A. S. K. Hashmi, L. Schwarz, J.-H. Choi, T. M. Frost,
Angew. Chem. Int. Ed. 2000, 39, 2285; b) Y. Liu, F.
Song, Z. Song, M. Liu, B. Yan, Org. Lett. 2005, 7, 5409.
[31] a) B. Seiller, C. Bruneau, P. H. Dixneuf, J. Chem. Soc.,
Chem. Commun. 1994, 493; b) B. Seiller, C. Bruneau,
P. H. Dixneuf, Tetrahedron 1995, 51, 13089; c) H. Kü-
cükbay, B. Cetinkaya, S. Guesmi, P. H. Dixneuf, Orga-
nometallics 1996, 15, 2434; d) B. C¸ etinkaya, I. Özdemir,
C. Bruneau, P. H. Dixneuf, J. Mol. Catal. A: Chem.
1997, 118, L1L4; e) B. C¸ etinkaya, B. Alici, I. Özdemir,
C. Bruneau, P. H. Dixneuf, J. Organomet. Chem. 1999,
575, 187; f) B. C¸ etinkaya, I. Özdemir, C. Bruneau, P. H.
Dixneuf, Eur. J. Inorg. Chem. 2000, 29; g) B. C¸ etinkaya,
N. Gürbüz, T. SeÅkin, I. Özdemir, J. Mol. Catal. A:
Chem. 2002, 184, 31.
[23] It is worthy of mention that no conversion at all has
been observedwhen these reactions are performedin
the absence of KO-t-Bu. The use of a basic media in
metal-catalyzedallylic alcohols isomerization is usually
required, see ref.[19]
[24] Due to the hydrophobicity of the allylic alcohols a bi-
phasic system (substrate/water) is formed. Since the
ruthenium catalysts are mainly dissolved in the aqueous
phase, the catalytic reaction most probably takes place
at the interphase.
[25] Conductivity measurements performed in water for
complexes
4a–d
(LM
values
from
18
to
60 WÀ1 cm2 molÀ1) clearly evidence their ability to par-
tially dissociate a chloride ligand in a polar solvent; see
also: P. Csabai, F. Joó, Organometallics 2004, 23, 5640.
[26] a) H. Heaney, J. S. Ahn, in: Comprehensive Heterocy-
clic Chemistry II, Vol. 2, (Eds: A. R. Katritzky, C. W.
Rees, E. F. V. Scriven), Pergamon Press, Oxford, 1996,
pp. 297; b) X. L. Hou, H. Y. Cheung, T. Y. Hon, P. L.
Kwan, T. H. Lo, S. Y. Tong, H. N. C. Wong, Tetrahedron
1998, 54, 1955.
[27] a) B. H. Lipshutz, Chem. Rev. 1986, 86, 795; b) R. Be-
nassi, in: Comprehensive Heterocyclic Chemistry II,
Adv. Synth. Catal. 2006, 348, 1671 – 1679
ꢁ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
1679