Barbier reaction in the regime of metal oxide: The first example of carbonyl allylation mediated by tetragonal tin(II) oxide

Article abstract of DOI:10.1039/b104500h

Facile synthesis of homoallylic alcohols is achieved from allyl halides and aldehydes or ketones over an all-oxide heterogenous media involving β-SnO and catalytic Cu₂O.

Full text of DOI:10.1039/b104500h

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Barbier reaction in the regime of metal oxide: the first example of
carbonyl allylation mediated by tetragonal tin(II) oxide†
Pradipta Sinha and Sujit Roy*
Organometallics & Catalysis Laboratory, Chemistry Department, Indian Institute of Technology,
Kharagpur 721302, India. E-mail: sroy@chem.iitkgp.ernet.in; Fax: +91 3222 82252;
Tel: +91 3222 83338
Received (in Cambridge, UK) 22nd May 2001, Accepted 25th July 2001
First published as an Advance Article on the web 4th September 2001
Facile synthesis of homoallylic alcohols is achieved from
allyl halides and aldehydes or ketones over an all-oxide
heterogenous media involving b-SnO and catalytic Cu2O.
yield (Table 1, entry 3).8 Under identical conditions, un-
catalyzed reaction affords < 15% of the product. Also important
is the remarkable effect of water: reaction in the presence of
catalyst 4a but in dry THF yields < 15% of the product, while
reaction in water alone gives rise to 55% of the desired alcohol.
That there is no phase change of b-SnO before and after
treatment with THF–water, is indicated by XRD. Among the
other catalysts screened, NiCl2(PPh3)2, PdCl2(PhCN)2 and
Pd2(dba)3·CHCl3 are found unsatisfactory ( < 25% yields), but
PdCl2(PPh3)2, Pd2(dba)3, and CuCl afford moderate to excellent
yields of product. The generality of the reaction has been
successfully tested with aliphatic, aromatic and heteroaromatic
aldehydes and substituted allyl bromides (Table 2, entry 1–5).
The reaction of a carbonyl compound and an organic halide in
the presence of magnesium metal, trivially known as the Barbier
reaction, has carved a distinct niche in synthetic organic and
pharmaceutical chemistry.1 In the hundred years, since its
original discovery,2 this one-pot variant of the Grignard
reaction has been demonstrated solely with zerovalent metals,
and metal halides.3 With specific reference to carbonyl
allylation via tin reagents,4 both preformed as well as in situ
generated allylstannanes continue to evoke widespread5 interest
due to their chemo-, regio-, stereo-, and enantioselecivity
aspects. Our continuing interest6 in organotin chemistry and
recent interest in heterobimetallic reagents, prompted us to
explore a gateway into the Barbier reaction via metal oxides.
We are delighted to disclose herein a facile carbonyl allylation
reaction over tetragonal tin(II)oxide (b-SnO)7 and catalytic
Table 2 Allylation of various carbonyl compounds with b-SnO/catalyst
Yield
#
1
Halide
Carbonyl
Cat Product
(%)
Pt(II), Pd(II), Pd(0), Cu( ) salts/complexes in organic–aqueous or
I
Fc-CHO
4a
3b
70
aqueous medium (Scheme 1). Further extension to b-SnO/
catalytic Cu2O affords an all-oxide reagent in Barbier allyl-
ation. We believe that the results provide new directions in the
synthetic and mechanistic issues of Grignard type carbon–
carbon bond forming reactions across metal oxides.
1b
1b
2b
2
3
4a
3c
65
63
2c
The model reaction of 1-bromoprop-2-ene 1a (2 mM) and
4-chlorobenzaldehyde 2a (1 mM) in the presence of catalytic
PtCl2(PPh3)2 4a (0.01 mM) and b-SnO (1.5 mM) in THF–water
(9+1 v/v) at 70 °C for 6 h gives rise to the desired homoallylic
alcohol 1-(4-chlorophenyl)but-3-ene-1-ol 3a in 96% isolated
4a
3d
1c
2d
4
5
BnCHO
4b
3e
53
76
1d
1d
2e
Scheme 1
4b
3f
Table 1 b-SnO promoted carbonyl allylation: effect of catalyst
2f
6
1c
4c
3g
79
2g
#
X
Catalyst
Solvent
Yield (%)
7
8
1c
1a
Me(CH2)8CHO 4c
54
71
1
2
3
4
5
6
7
Br
Br
Br
Br
Br
Cl
Br
NIL
PtCl2(PPh3)3 4a
4a
THF–H2O
THF
15
15
96
76
80
52
33
2h
3h
3i
THF–H2O
THF–H2O
DCM–H2O
DCM–H2O
THF–H2O
Pd2(dba)3 4b
Cu2O 4c
4c
4c
2i
CuCl 4d
9
1a
4c
45
† Electronic supplementary information (ESI) available: further experi-
mental details, XRD and EIMS spectra. See http://www.rsc.org/suppdata/
cc/b1/b104500h/
2j
3j
1798
Chem. Commun., 2001, 1798–1799
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b104500h

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Scheme 2 p-Allylpalladium attacks tetragonal tin(II) oxide.
and C (1s) peaks.12 Multi-Gaussian peak analysis of carbon-1s
spectra shows two new peaks at 280.8 and 283.2 eV (Fig. 2,
spectrum b) indicative of metal–carbon bonded species. Prior
interaction of alkene with copper( ) is likely to promote the
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formation of an allyltin intermediate.13 We hope to address this
and related mechanistic issues in future studies.
We thank CSIR, UGC and DST for financial support.
Notes and references
Fig. 1 1H NMR spectra in DMSO-d6 of (a) allyl bromide; (b) residue from
the reaction of b-SnO–allyl bromide; (c) residue from the reaction of b-
SnO–allyl bromide–catalytic Pd2(dba)3 [dba = dibenzylideneacetone].
1 B. J. Wakefield, Organomagnesium Methods in Organic Chemistry,
Academic Press, New York, 1995; R. D. Rieke, Science, 1989, 246,
1260; C. J. Li and W.-C. Zhang, J. Am. Chem. Soc., 1998, 120, 9102.
2 P. Barbier, Competus Rendus, 1898, 128, 110; V. Grignard, Competus
Rendus, 1900, 130, 1322.
3 For representative examples, please see: T. H. Chan and Y. Yang, J. Am.
Chem. Soc., 1999, 121, 3228; X.-H. Yi, Y. Meng, X-G. Hua and C. J. Li,
J. Org. Chem., 1998, 63, 7472; A. Yanagisawa, S. Habaue, K. Yasue
and H. Yamamoto, J. Am. Chem. Soc., 1994, 116, 6130; D. P. Curran,
X. Gu, W. Zhang and P. Dowd, Tetrahedron, 1997, 53, 9023; F. Dubner
and P. Knochel, Angew. Chem., Int. Ed., 1999, 38, 379.
4 For reviews please see: W. R. Rousch, in Comprehensive Organic
Synthesis, eds. B. M. Trost, I. Fleming and C. H., Heathcock, Pergamon
Press, Oxford, 1991, vol. 2, pp. 1–53 and related chapters; Y.
Yamamoto and N. Asao, Chem. Rev., 1993, 93, 2207; J. A. Marshall,
Chem. Rev., 1996, 96, 31; E. J. Thomas, Chemtracts-Org. Chem., 1994,
7, 207; Y. Masuyama, in Advances in Metal-Organic Chemistry, ed.
L. S. Liebeskind, JAI Press, Greenwich CT, 1994.
5 For representative examples, please see: (a) G. E. Keck, K. H. Tarbet
and L. S. Geraci, J. Am. Chem. Soc., 1993, 115, 8467; (b) A.
Yanagisawa, H. Inoue, M. Morodome and H. Yamamoto, J. Am. Chem.
Soc., 1993, 115, 10 356; (c) A. Ito, M. Kishida, Y. Kurusu and Y.
Masuyama, J. Org. Chem., 2000, 65, 494; (d) J. P. Takahara, Y.
Masuyama and Y. Kurusu, J. Am. Chem. Soc., 1992, 114, 2577; (e) T. H.
Chan, Y. Yang and C. J. Li, J. Org. Chem., 1999, 64, 4452.
6 (a) P. Sinha, A. Kundu, S. Roy, S. Prabhakar, M. Vairamani, A. R.
Sankar and A. C. Kunwar, Organometallics, 2001, 20, 157; (b) A.
Kundu and S. Roy, Organometallics, 2000, 19, 105; (c) A. Kundu, S.
Prabhakar, M. Vairamani and S. Roy, Organometallics, 1999, 18, 2782;
(d) A. Kundu, S. Prabhakar, M. Vairamani and S. Roy, Organome-
tallics, 1997, 16, 4796.
Fig. 2 XPS spectra in the C-1s region of (a) untreated b-SnO/Cu2O—peaks
at 284.5, 287.6; (b) b-SnO/Cu2O after treatment with allyl bromide—peaks
at 280.8, 283.2, 284.5, 288.9.
Triggered by the success as above, we wished to attempt an all-
oxide reagent for carbonyl allylation. The reagent combination
of b-SnO and catalytic Cu2O in refluxing DCM–water (9+1 v/v)
is adjudged to be the best (Table 1, entry 5–6; Table 2, entry
6–9).
While mechanistic studies are underway in our laboratory,
preliminary experiments clearly establish the formation of new
tin–carbon bonded species during the course of the reaction.
Thus, a mixture of b-SnO (2 mM), catalytic Pd2(dba)3 (0.02
mM) and allyl bromide (4 mM) in THF–H2O (99+1 v/v) was
refluxed for 10 h. Following filtration under argon, and solvent
removal, the residue was examined by 1H NMR. The spectrum
(Fig. 1, spectrum c) showed the formation of a new s-allyl tin
species9 characterized by allylic proton signals at 2.55 ppm
[2J(119Sn–1H) = 154 Hz], as compared to that of allyl bromide
at 4.1 ppm (spectrum a). No such species was detected in the
reaction without catalyst (Fig. 1, spectrum b). On the other
hand, reaction of allyl bromide with Pd2(dba)3 alone, showed
signals due to known p-allylpalladium intermediate.10 We
conclude that the latter assists the formation of the s-allyl tin
species (Scheme 2).11
Unlike the above, we could not detect any soluble organotin
species in the reaction of allyl bromide with b-SnO/catalytic
Cu2O, thereby indicating that the incipient metal–carbon
intermediate is formed in the solid phase. To test this
hypothesis, narrow scan XPS analysis was performed for b-
SnO/Cu2O before and after its reaction with allyl bromide.
Formation of new species is indicated by major shifts in the
binding energies of Sn (3d5/2, 3d3/2), Cu (2p3/2, 2p1/2), O (1s)
7 For chemistry of bivalent tin, please see: J. D. Donaldson, Prog. Inorg.
Chem., 1967, 8, 287; P. J. Harrison, Chemistry of Tin, Blackie, New
York, 1989, pp. 221–244.
8 Typical procedure: a mixture of 1a (242 mg, 2 mM) and 2a (140 mg, 1
mM) in THF (2 mL) was added slowly to a refluxing solution containing
b-SnO (202 mg, 1.5 mM) and 4a (8 mg, 0.01 mM) in THF–H2O (2.5
mL–0.5 mL) and under argon. Upon completion (TLC monitoring:
silica gel, eluent: n-hexane–EtOAc 9+1), an aqueous solution of NH4F
(15%, 10 mL) was added to the reaction mixture and the organic layer
was extracted with diethyl ether (3 3 10 mL), washed with water (2 3
10 mL), brine (2 3 10 mL) and dried over magnesium sulfate. Solvent
removal followed by column chromatography (eluent n-hexane–ethyl
acetate 9+1) afforded pure 3a (175 mg, 96% w.r.t. aldehyde). Similar
procedure as above was followed for reactions with Cu2O as catalyst (14
mg, 0.1 mM), the solvent used was CH2Cl2–H2O (4.5 mL–0.5 mL).
9 For comparison with known s-allyl tin NMR, please see: refs. 5d, 5e and
6d.
10 The Organic Chemistry of Palladium, ed. P. Maitilis, Vol. 1, 2,
Academic Press, New York, 1971.
11 Direct injection of a reaction mixture into an EIMS probe results in
major peaks at 351, 430, 478 corresponding to possible fragments
[(allyl)2Sn2O2 2 H]+, [(allyl)2Sn2O2Br 2 H]+, and [(allyl)2Sn2Br2]+.
12 Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of
Standard Data for Use in XPS, Perkin–Elmer Corporation Physical
Electronics Division, 1979.
13 For olefin-Copper( ) interaction see: ref. 6d.
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