Organometallic Reactions in Aqueous Media
J . Org. Chem., Vol. 64, No. 12, 1999 4455
ceric sulfate (1 g) in concentrated H2SO4/H2O (10 mL/90 mL)
and heated with a heat gun.
(d ) Syn th etic Im p lica tion s. These results demon-
strate quite convincingly that both allyltin(I) bromide (5)
and diallyltin dibromide (4) are formed as organotin
intermediates in the aqueous Barbier reaction of allyl
bromide and tin. Either 4 or 5 can react with carbonyl
compounds to give the corresponding homoallylic alco-
hols. These results however do not eliminate the pos-
sibility of a parallel process of metal surface mediated
radical or radical anion reactions.20 Nevertheless, the
understanding that the reaction can proceed through an
organotin intermediate has useful synthetic applications.
For example, p-nitrobenzaldehyde is known to be reduced
under the metallic tin conditions and cannot undergo the
aqueous Barbier allylation reaction.21 However, diallyltin
dibromide (4) cleanly allylated p-nitrobenzaldehyde to the
corresponding alcohol 8 (Table 1, entry 3) in nearly
quantitative yield. Another example is that R-bromocar-
bonyl compounds are usually reduced by metallic tin.22
However, compound 4 reacted cleanly with ethyl R-bro-
mopyruvate to give the allylation product 17 in excellent
yield (entry 12). Finally, in the aqueous Barbier reaction
with carbohydrate compounds, because the aldehydic
form of the carbohydrate is often present in low concen-
tration in its equilibrium with the cyclic acetal form, the
reaction may sometimes proceed in low yield.23 The use
of a higher concentration of preformed diallyltin dibro-
mide can improve the yield of the allylation reaction as
demonstrated in the formation of compounds 18 and 19
(entries 13 and 14). Finally, reactive R-dicarbonyl com-
pounds such as glyoxal reacted under the aqueous
Barbier conditions to give complex mixtures of products
due to the ease of the carbonyl functions to undergo
reduction and pinacol coupling mediated by metal. How-
ever, with diallyltin dibromide, the allylation reaction
(entry 5) proceeded uneventfully to give the diol 10 with
good diastereoselectivity in high yields.
Solvents were reagent grade unless otherwise specified.
THF was dried and distilled from Na. Tin powder (150 mesh,
99.99%, 100 g packing) was freshly opened for use. Carbonyl
compounds were checked for purity by 1H NMR and were
distillated or recrystallized if impure. Diallyltin dibromide was
prepared following the method reported in the literature.24
Gen er a l Meth od for Allyla tion of Ca r bon yl Com -
p ou n d s in Aqu eou s Med ia . To a mixture of carbonyl
compound (1 mmol) in water (3-5 mL) was added diallytin
dibromide (0.6-1 mmol) at room temperature. The mixture
was stirred overnight and quenched with 1 N HCl (1 mL)
solution. The mixture was extracted with ether (3 × 10 mL),
and the combined organic layer was washed with saturated
aqueous NaHCO3 solution and dried. The organic solvent was
evaporated, and the product homoallylic alcohol was usually
obtained pure according to 1H NMR and can be further purified
by flash chromatography on silica gel if necessary. All the
products except 17 obtained in this work are known com-
pounds, so the structures were determined by comparison of
their 1H and 13C NMR spectral data with those given in the
literatures: R-2-propenylbenzenemethanol25 (6), 1-decene-4-
ol26 (7), 4-chloro-R-2-propenylbenzenemethanol27 (12), R-pro-
penylcyclohexanemethanol28 (9), 1,7-octadiene-4,5-diol29 (10),
1-phenyl-1,5-hexadien-3-ol21 (11), R-methyl-R-2-propenyl-
benzenemethanol30 (13), 3-methyl-5-hexen-3-ol30 (14), 5-(2-
propenyl)-5-nonanol31 (15), 2-methyl-1-(2-propenyl)cyclo-
hexanol32 (16), p-nitro-R-2-propenylbenzenemethanol33 (8),
1,2,3-trideoxy-D-mann-non-1-enitol34 (18), 1,2,3-trideoxy-L-ara-
bino-oct-1-enitol19 (19).
4-P en ten oic acid, 2-h ydr oxy-2-(br om o-)m eth ylen e, eth -
yl ester (17): 1H NMR (200 MHz CDCl3) δ 5.78(m, 1H), 5.12-
(m, 2H), 4.25(q, J ) 7.30 Hz, 2H), 3.45-3.60(m, 2H), 3.55(s,
1H), 2.52(m, 2H), 1.38(t, J ) 7.30 Hz, 3H); 13C NMR (50 MHz
CDCl3) δ 172.54, 131.56, 119.84, 77.60, 63.52, 43.23,40.28,
15.85; IR (KBr) ν(cm-1) 3522, 2982, 1736, 1438,1292, 1230,
1182, 1095, 919, 648 MS(CI) m/z 237 (M + 1); HRMS(CI) calcd
for C8H14O3Br (M + H) 237.01263, found 237.01271.
Ack n ow led gm en t. We thank NSERC for financial
support of this research.
Exp er im en ta l Section
J O9901337
Analytical thin-layer chromatography (TLC) was performed
on silica gel 60 F254 plastic-backed plates and was visualized
by dipping into a solution of ammonium molybdate (2.5 g) and
(24) Sisido, K.; Takeda, Y. J . Org. Chem. 1961, 2301.
(25) Araki, S.; Ito, H.; Butsugan, Y. J . Organomet. Chem. 1988, 347,
5.
(19) Tetraallytin also reacts with carbonyl compounds in aqueous
media to give the homoallylic alcohols. However, the reaction requires
Lewis acid catalyst. Hachiya, I.; Kobayashi, S. J . Org. Chem. 1993,
58, 6958.
(20) Recently, allylation of aldehydes with magnesium in water has
been observed. Both allylmagnesium intermediate and metal surface
reaction have been invoked to account for the formation of the products.
See: Li, C.-J .; Zhang, W. C. J . Am. Chem. Soc. 1998, 120, 9102.
(21) Chan, T. H.; Issac, B. M. Pure Appl. Chem. 1996, 68, 919.
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aqueous media, see: (a) Chan, T. H.; Li, C. J .; Wei, Z. Y. Can. J . Chem.
1994, 72, 1181. (b) Bieber, L. W.; Malvestiti, I.; Storch, E. C. J . Org.
Chem. 1997, 62, 9061.
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