Catalytic Barbier-type reactions of lactones and esters mediated by the Mischmetall/SmI2(cat.) system or the Mischmetall/[SmI2/NiI2(cat'.)](cat.) system

Article abstract of DOI:10.1016/S0040-4039(02)01979-2

Barbier-type reactions using SmI₂ in catalytic amounts together with Mischmetall as a coreductant, involving lactones or esters and a variety of organic halides (allylic, benzylic and alkyl), have been performed. With alkyl halides and five- or six-membered ring lactones, catalytic quantities of nickel diiodide (with respect to SmI₂) must be added to achieve reactions. Thus, a 'two-stage catalysis' is carried out. Unexpectedly, it was found that with esters or an unstrained lactone the Mischmetall/SmI₂ (catalytic) system is more reactive than samarium diiodide in stoichiometric amounts. Tentative interpretations of the catalytic role of NiI₂ are proposed.

Full text of DOI:10.1016/S0040-4039(02)01979-2

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 8007–8010
Catalytic Barbier-type reactions of lactones and esters mediated
by the Mischmetall/SmI2(cat.) system or the
Mischmetall/[SmI2/NiI2(cat%.) (cat.) system
]
Marie-Isabelle Lannou, Florence He´lion and Jean-Louis Namy*
Laboratoire de Catalyse Mole´culaire, associe´ au CNRS, ICMO, Bat 420, Universite´ Paris-Sud, 91405, Orsay, France
Received 11 September 2002; accepted 13 September 2002
Abstract—Barbier-type reactions using SmI2 in catalytic amounts together with Mischmetall as a coreductant, involving lactones
or esters and a variety of organic halides (allylic, benzylic and alkyl), have been performed. With alkyl halides and five- or
six-membered ring lactones, catalytic quantities of nickel diiodide (with respect to SmI2) must be added to achieve reactions. Thus,
a ‘two-stage catalysis’ is carried out. Unexpectedly, it was found that with esters or an unstrained lactone the Mischmetall/SmI2
(catalytic) system is more reactive than samarium diiodide in stoichiometric amounts. Tentative interpretations of the catalytic role
of NiI2 are proposed. © 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
Recently, SmI2 in the presence of catalytic amounts of
NiI2 has also been used to promote intramolecular
conjugate additions of alkyl halides onto a,b-unsatu-
rated lactones.5
We have recently reported that Mischmetall is an
efficient coreductant in samarium diiodide-catalysed
reactions. With the Mischmetall/SmI2 (catalytic) sys-
tem, Barbier-type reactions have been achieved accord-
ing to a catalytic Barbier procedure (Catalytic-BP).1
Sequential reactions could also be achieved in the pres-
ence of this system and allylic or benzylic halides with
ketones aldehydes or esters. In that case the procedure
can be termed a catalytic Grignard procedure (Cata-
lytic-GP).2 Besides, it has been shown that lactones and
esters are poor electrophiles in stoichiometric samarium
diiodide-mediated reactions.3 However, Barbier-type
reactions involving lactones or esters and alkyl halides
yield the expected products in the presence of small
amounts of nickel diiodide (1 mol% with respect to
SmI2) (Scheme 1).4
Here we report some Barbier-type reactions of lactones
or esters performed with samarium diiodide in catalytic
amounts together with Mischmetall as the coreductant.
2. Results and discussion
We first studied reactions of lactones with activated
halides (allyl bromide and benzyl bromide) mediated by
the Mischmetall/SmI2 (catalytic) system using a Cata-
lytic-BP and readily observed the formation of diols.
The results are collected in Table 1.
Yields of diols7 were good or excellent, except with
coumarin (entries 7 and 8) and 5H-furan-2-one (entry
11), which gave a mixture of unidentified by-products
This experimental process can be termed a NiI2-
catalysed Barbier procedure (BP/NiI2(cat.)).
Scheme 1.
Keywords: Barbier reactions; catalysis; lactones; nickel diiodide; mischmetall; samarium diiodide.
* Corresponding author. Fax: +33-1-69-15-4680; e-mail: jelonamy@icmo.u-psud.fr
0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)01979-2

8008
M.-I. Lannou et al. / Tetrahedron Letters 43 (2002) 8007–8010
Table 1. Catalytic Barbier-type reactions of lactones with
(in reaction between coumarin and benzyl bromide, the
main product was dibenzyle obtained in 15% yield). In
the absence of samarium diiodide, the starting materials
were recovered unchanged, indicating that reactions are
not mediated by lanthanide metals. Nickel diiodide was
not required for these reactions. This feature is not
really surprising, since it is well known that allylic and
benzylic halides are very reactive in samarium diiodide-
mediated Barbier-type reactions. Next, we examined the
reactions of the less active alkyl halides. We anticipated
a catalytic amount of NiI2 (with respect to SmI2) would
be necessary. Therefore, the Mischmetall/[SmI2/
activated halides6
Entry
RX
Electrophile
Product: yield (%)a
1
2
3
4
5
6
7
8
9
AllylBr
BenzylBr
AllylBr
BenzylBr
AllylBr
BenzylBr
AllylBr
g-Butyrolactone
g-Butyrolactone
o-Caprolactone
o-Caprolactone
Dihydrocoumarin
Dihydrocoumarin
Coumarin
72
78
78
72
1: 88
95
2: 20
0
3: 42
NiI2(cat%.) (cat.)
]
system was used in a catalytic Barbier
procedure catalysed with NiI2 (Catalytic-BP/NiI2(cat.)
)
and compared to the Mischmetall/SmI2(cat.) system in a
catalytic Barbier procedure (Catalytic-BP).
BenzylBr
AllylBr
Coumarin
The results are collected in Table 2.
We checked that both Mischmetall alone and Mis-
chmetall in the presence of nickel diiodide (without
SmI2) were unreactive in the reactions indicated above.
In several cases (entries 1, 3, 8 and 10) minor amounts
of diols7 (6–30%) resulting from the addition of a THF
moiety onto lactones were detected (Scheme 2).
10
11
BenzylBr
AllylBr
¦
90
4: 13
a Isolated yields.
Table 2. Catalytic Barbier-type reactions of lactones or esters with alkyl halides
Entry
Electrophile
RX
Product: yield (%)a
Catalytic-BP/NiI2(cat.)
Catalytic-BPb
c
1
2
3
4
5
6
7
8
b-Propiolactone
d-Butyrolactone
d-Butyrolactone
d-Valerolactone
Coumarin
Dihydrocoumarin
Dihydrocoumarin
Dihydrocoumarin
o-Caprolactone
o-Caprolactone
Ethyl benzoate
tert-Butyl acetate
Ethyl iso-butyrate
1-Iodoheptane
1-Iodoheptane
1-Iodododecane
1-Iodoheptane
1-Iodoheptane
1-Iodoheptane
Iodoethane
1-Iodododecane
1-Iodoheptane
1-Iodododecane
1-Iodoheptane
1-Iodoheptane
1-Iodoheptane
37d
0
47d
83
0e
0
71f
66
0
0
0
0
5: 80
60
0e
91
80h
74
70
76
78g
68
9
10
11
12
13
48i
78
72
81
a Isolated yields.
b For the experimental procedure, see Ref. 6.
c For the experimental procedure see Ref. 6, except that before addition of an alkyl halide, NiI2 (0.035 mmol) in THF (3.5 mL) was added and
the mixture was then stirred for 10 min.
d 3-(Tetrahydrofuran-2-yl)-decane-1,3-diol: (6) was also obtained in 30% yield.
e Wurtz coupling of iodododecane occurred.
f 4-(Tetrahydrofuran-2-yl)-hexadecane-1,4-diol: was also obtained in 14% yield.
g 2-[3-Hydroxy-3-(tetrahydrofuran-2-yl)-pentadecyl]-phenol was also obtained in 15% yield.
h 6-(Tetrahydrofuran-2-yl)-octadecane-1,6-diol was also obtained in 6% yield.
i 6-(Tetrahydrofuran-2-yl)-octadecane-1,6-diol was also obtained in 12% yield.

M.-I. Lannou et al. / Tetrahedron Letters 43 (2002) 8007–8010
8009
with SmI2) accelerates the formation of an organosa-
marium reagent as well as facilitating its addition onto
esters or lactones (Scheme 3).
Scheme 2.
In Catalytic-BP (Mischmetall with SmI2 in catalytic
amounts), an organosamarium reagent is initially pro-
duced (along with SmI3). Its reaction with a lanthanide
metal (Ln=Ce, La, Nd, Pr) regenerates SmI2 and fur-
nishes another organolanthanide species, which is able
to react with esters and o-caprolactone but not with five
or six-membered-ring lactones (Scheme 4).
The results (entries 2–8) obtained with the five- or
six-membered ring lactones were in good agreement
with the expectations since good yields in diols7 were
obtained with nickel diiodide, whereas in the absence of
this catalyst, starting materials were recovered
unchanged. Thus, this ‘double-stage catalysis’ is
efficient in those cases. In contrast, with b-propiolac-
tone, the diol was obtained as well in Catalytic-BP and
Catalytic-BP/NiI2(cat.). However, due to the strain on
the cycle, it is known that this lactone reacts in a
peculiar way in the presence of lanthanide salts.8 More
unexpectedly, the diols were obtained with o-caprolac-
tone in excellent yield in the absence of nickel diiodide.
It was thus anticipated that esters should behave as this
unstrained lactone. This was confirmed by the results
reported in entries 11, 12 and 13: good yields in tertiary
alcohols were obtained in both procedures. Thus, with
o-caprolactone and esters the catalytic Barbier proce-
dure does not require the presence of nickel diiodide,
while the stoichiometric Barbier procedure demands it.
These results are difficult to explain, since the precise
part of NiI2 in samarium diiodide-mediated reactions
has not been cleared up. However, the following
hypotheses can be proposed.
In Catalytic-BP/NiI2(cat.), NiI2 catalyses both processes:
formation of an organosamarium compound and sub-
sequent addition of organolanthanide to electrophiles
including five- or six-membered ring lactones (Scheme
5).
In conclusion, catalytic Barbier-type reactions with
SmI2 in catalytic amounts and Mischmetall as a core-
ductant have been performed between lactones (and
esters) and a variety of organic halides (allylic, benzylic
and alkyl halides). With an alkyl halide, a catalytic
quantity of nickel diiodide (with respect to SmI2) must
be added in some cases to achieve reactions. Then a
‘two-stage catalysis’ is carried out. However, it was
found that nickel diiodide is not always necessary,
showing that the Mischmetall/SmI2 (catalytic) system
can be more reactive than samarium diiodide in stoi-
chiometric amounts. We are currently studying the
mechanisms involved in those catalytic reactions.
In BP (SmI2 in stoichiometric amounts, without NiI2),
an organosamarium reagent is slowly produced. Due to
its low reactivity towards esters and lactones, it reacts
preferentially with the solvent (THF) giving a hydrocar-
bon and the expected alcohol does not form.
In BP/NiI2(cat.) (SmI2 in stoichiometric amounts, in the
presence of NiI2 in catalytic amounts), NiI2 (or another
nickel derivative which could result from a reaction
Scheme 5.
Scheme 3.
Scheme 4.

8010
M.-I. Lannou et al. / Tetrahedron Letters 43 (2002) 8007–8010
1228, 1170. GC–MS m/z (% base peak): 41 (70), 77 (12),
Acknowledgements
91 (46), 103 (46), 115 (12), 147 (100), 171 (22), 189 (22),
230 (1). HRMS (IE) calcd for C15H18O2: 230.1307, found:
We are indebted to Dr. J. Collin for fruitful discussions.
We thank the University of Paris-Sud and the CNRS
for their financial support and Mr. J.-P. Baltaze for
technical help.
230.1310.
cis-3-(2-Allyl-2-hydroxy-pent-4-enyl)-cyclopen-
1
tanol (3): H NMR (250 MHz, CDCl3) l (ppm): 1.19–2.04
(9H, C(1)OH, C(2)H2, C(3)H, C(4)H2, C(5)H2, C(2%)OH);
1.62 (2H, d, C(1%)H2, J1%–3=6.4 Hz); 2.24 (4H, d, C(3%)H2,
CH
(4H, m, C(5%)H2, CH2-CHꢀCH2
CH2-CHꢀCH2
). 13C NMR (63 MHz, CDCl3) l (ppm):
6
2-CHꢀCH2, J3%–4%=6.8 Hz); 4.29 (1H, m, C(1)H); 5.12
6
); 5.85 (2H, m, C(4%)H,
References
6
32.1; 34.0; 35.4; 43.9, 44.0; 44.3; 45.6; 73.4; 73.9; 118.8;
133.9. FTIR (CaF2) wmax: 3369, 3075, 3006, 2930, 2858,
1832, 1711, 1640, 1441, 1420, 1295. GC–MS (IC-NH3) m/z
(% base peak): 151 (26), 175 (55), 192 (18), 193 (100), 210
(11), 211 (8). HRMS (IE) calcd for C13H22O2–H2O:
192.1514, found: 192.1509. 4-Allyl-hepta-2,6-diene-1,4-diol
1. He´lion, F.; Namy, J. L. J. Org. Chem. 1999, 64, 2944–
2946.
2. Di Scala, A.; Garbacia, S.; He´lion, F.; Lannou, M.-I.;
Namy, J. L. Eur. J. Org. Chem. 2002, 2989–2995.
3. Krief, A.; Laval, A.-M. Chem. Rev. 1999, 745–777.
4. Machrouhi, F.; Hamann, B.; Namy, J. L.; Kagan, H. B.
Synlett 1996, 633–634.
1
(4): H NMR (250 MHz, CDCl3) l (ppm): 2.31 (1H, br s,
OH); 2.32 (4H, d, C(5)H2, CH2
3.37 (1H, br s, OH); 4.25 (2H, dd, C(1)H2, J1–2=5.9 Hz,
4J1–3=1.5 Hz); 5.11 (4H, m, C(7)H2, CH2-CHꢀCH2
); 5.44
6 -CHꢀCH2, J5–6=7.3 Hz);
5. Molander, G. A.; St Jean, D. J., Jr. J. Org. Chem. 2002,
67, 3861–3865.
6
6. Mischmetall powder (0.7 g, 5 mmol) was suspended in
THF (7 mL), with 0.7 mmol of SmI2 in a Schlenk tube
under argon at room temperature. A solution of an elec-
trophile (lactone, 2 mmol) and an organic halide (4 mmol)
in THF (7 mL) was slowly added over 2.5 h to the
THF/SmI2/Mischmetall suspension. The mixture was then
stirred for an additional period of 0.5 h, then diluted with
ether, quenched with HCl (1 M) and stirred for 15 min to
obtain a clear solution, which was extracted with ether.
The combined extracts were washed with brine, aqueous
sodium thiosulfate and brine again. The organic layer was
dried with MgSO4, and the solvents were removed under
reduced pressure. The crude material was purified by flash
chromatography on silica gel.
4
(1H, dd, C(3)H, J3–2=12.2 Hz, J3–1=1.5 Hz); 5.68 (1H,
dt, C(2)H, J2–3=12.2 Hz, J2–1=5.9 Hz); 5.83 (2H, m,
C(6)H, CH2-CH6
ꢀCH2). 13C NMR (63 MHz, CDCl3) l
(ppm): 45.9, 58.8, 75.1, 118.8, 129.3, 133.3, 136.1. FTIR
(NaCl) wmax: 3354, 3076, 3012, 2997, 2928, 1640, 1438,
1219, 1028, 997, 916. GC–MS (IE) m/z (% base peak): 41
(100), 53 (33), 57 (26), 79 (50), 81 (47), 85 (94), 109 (37),
127 (42). HRMS (IE) calcd for C10H16O2–H2O: 150.1045,
found: 150.1044. 2-(3-Heptyl-3-hydroxydecyl)-phenol (5):
1H NMR (250 MHz, CDCl3) l (ppm): 0.97 (6H, t,
C(10%)H3, CH3
C(5%)H2, C(6%)H2, C(7%)H2, C(8%)H2, C(9%)H2, CH2-(CH2 5
CH3); 1.40 (4H, m, C(4%)H2, C(3%)OH-CH2-C6H13); 1.82
6
-nC6H13, J10%–9%=6.8 Hz); 1.35 (20H, m,
6
) -
6
(2H, m, C(2%)H2); 2.74 (2H, m, C(1%)H2); 2.94 (1H, br s,
C(3%)OH); 6.32 (2H, m, Har); 7.14 (2H, m, Har); 7.88 (1H,
br s, C(1)OH). 13C NMR (63 MHz, CDCl3) l (ppm): 14.0;
22.6; 23.6; 24.1; 29.2; 30.1; 31.8; 38.7; 39.2; 75.6; 116.1;
120.2; 127.1; 129.0; 129.9; 153.9. FTIR (CaF2) wmax: 3306,
3032, 2929, 2857, 1924, 1889, 1776, 1594, 1584, 1490, 1457,
1378, 1242. GC–MS (IE) m/z (% base peak): 41 (27), 43
(28), 77 (10), 107 (100), 133 (8), 231 (70), 249 (10), 330 (4).
HRMS (IE) calcd for C23H40O2–H2O: 330.2923, found:
330.2918. 3-(Tetrahydrofuran-2-yl)-decane-1,3-diol (6): 1H
NMR (200 MHz, CDCl3) l (ppm): 0.88 (3H, t, C(10)H3,
7. Selected spectral data. 2-(3-Allyl-3-hydroxy-hex-5-enyl)-
phenol (1): 1H NMR (250 MHz, CDCl3) l (ppm): 1.76
(2H, m, C(2%)H2); 2.30 (4H, m, C(4%), CH6 2-CHꢀCH2); 2.65
(1H, s, C(3%)OH); 2.71 (2H, m, C(1%)H2); 5.13 (4H, m,
C(6%)H2, CH2-CHꢀCH2); 5.88 (2H, m, C(5%)H, CH2-
CH6 ꢀCH2); 6.85 (2H, m, Har); 7.10 (2H, m, Har); 7.19 (1H,
s, C(1)OH). 13C NMR (63 MHz, CDCl3) l (ppm): 24.2;
38.9; 43.4; 74.4; 116.0; 119.1; 120.4; 127.4; 128.5; 130.1;
133.2; 153.9. FTIR (CaF2) wmax: 3528, 3338, 3075, 3006,
2977, 2930, 2863, 1839, 1640, 1609, 1593, 1504, 1490, 1457,
1413, 1376, 1242, 1186. GC–MS (IE) m/z (% base peak):
41 (18), 77 (18), 107 (100), 121 (16), 149 (12), 173 (13), 191
(3), 232 (2). HRMS (IE) calcd for C15H20O2: 232.1463,
found: 232.1254. Z-2-(3-Allyl-3-hydroxy-hexa-1,5-dienyl)-
phenol (2): 1H NMR (250 MHz, CDCl3) l (ppm): 2.34
J10–9=8.8 Hz); 1.28 (10H, m, C(5)H2, C(6)H2, C(7)H2,
C(8)H2, C(9)H2); 2.03–1.37 (8H, m, C(2)H2, C(4)H2,
C(3%)H2, C(4%)H2); 2.38 (1H, s, C(3)OH); 3.10 (1H, s,
C(1)OH); 3.82 (5H, m, C(1)H2, C(2%)H, C(5%)H2). 13C
NMR (63 MHz, CDCl3) l (ppm): 14.0; 22.5; 23.9; 25.6;
26.1; 29.2; 30.2; 31.7; 35.3; 36.8; 58.9; 68.4; 75.8; 82.8.
FTIR (NaCl), wmax: 3386; 2926; 2856; 1464; 1378; 1288;
1186; 1130; 1070; 927; 877; 733. GC–MS (IE) m/z (% base
peak): 41 (82), 43 (83), 55 (48), 57 (95), 70 (15), 71 (86), 83
(12), 97 (21), 101 (8), 127 (55), 145 (16), 155 (27), 173
(100), 174 (11), 199 (9). HRMS (IE): calcd for C14H28O3–
H2O: 226, 1933; found: 226, 1934.
(1H, s, C(3%)OH); 2.34 (4H, d, C(4%)H2, CH2
6 -CHꢀCH2,
J=7.3 Hz); 5.13 (5H, m, C(1)OH, C(6%)H2, CH2-CHꢀCH2
6
,
J
trans=17.6 Hz, Jcis=10.3 Hz); 5.79 (1H, d, C(2%)H, J2%–1%
=
=
12.7 Hz); 5.85 (2H, ddt, C(5%)H, CH2-CHꢀCH2, Jtrans
6
17.1 Hz, Jcis=10.3 Hz, Jgem=7.3 Hz); 6.44 (1H, d, C(1%)H,
J1%–2%=12.7 Hz); 6.87 (2H, m, Har); 7.15 (2H, m, Har). 13C
NMR (63 MHz, CDCl3) l (ppm): 45.2; 75.4; 116.7; 119.4;
120.2; 124.7; 125.2; 128.7; 129.5; 133.0; 138.1; 152.5. FTIR
(CaF2) wmax: 3528, 3306, 3076, 3010, 2978, 2928 2849,
1838, 1698, 1640, 1604, 1586, 1576, 1502, 1450, 1414, 1364,
8. Machrouhi, F.; Namy, J. L. Tetrahedron 1998, 54, 11111–
11122.