The Barbier-Type Alkylation of Aldehydes with Alkyl Halides in the Presence of Metallic Strontium

Article abstract of DOI:10.1246/bcsj.77.341

In the presence of metallic strontium, the Barbier-type alkylation of aldehydes with alkyl iodides proceeded smoothly at - 15 °C under an argon atmosphere to afford the corresponding alkylated alcohols in moderate to good yields. The unusual addition reaction of ethyl benzoate with tert-butyl iodide took place to give the p-tert-butylated alkylated product (the 1,6-adduct of the benzoate) in 55% yield. Using strontium isopropoxide, the Meerwein-Ponndorf-Verley-type reduction of the aldehyde proceeded smoothly under reflux conditions in 2-propanol.

Full text of DOI:10.1246/bcsj.77.341

Ó 2004 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 77, 341–345 (2004)
341
The Barbier-Type Alkylation of Aldehydes with Alkyl Halides
in the Presence of Metallic Strontium
ꢀ
Daitetsu Ikehara, and Makoto Wada
Norikazu Miyoshi, Koji Kamiura, Hiromi Oka, Akiko Kita, Rika Kuwata,
Department of Chemistry, Faculty of Integrated Arts and Sciences, University of Tokushima,
1-1 Minamijosanjima, Tokushima 770-8502
Received August 4, 2003; E-mail: miyoshi@ias.tokushima-u.ac.jp
In the presence of metallic strontium, the Barbier-type alkylation of aldehydes with alkyl iodides proceeded smooth-
ly at ꢁ15 ꢂC under an argon atmosphere to afford the corresponding alkylated alcohols in moderate to good yields. The
unusual addition reaction of ethyl benzoate with tert-butyl iodide took place to give the p-tert-butylated alkylated product
(the 1,6-adduct of the benzoate) in 55% yield. Using strontium isopropoxide, the Meerwein–Ponndorf–Verley-type reduc-
tion of the aldehyde proceeded smoothly under reflux conditions in 2-propanol.
Organometallic compounds comprise some of the most ver-
satile reagents in organic synthesis, and among them are orga-
nometallic compounds of alkaline-earth elements.1,2 Numerous
reports have been published on the Grignard (or Barbier) reac-
tion using metallic magnesium and alkyl halides, which is one
of the most useful and convenient methods for performing alky-
lation of carbonyl compounds.3 Furthermore, there are various
reports on the preparation and reactivity of the organometallic
compounds of calcium and barium.2 In contrast, fewer studies
on the preparation and reactivity of organostrontium com-
pounds are found in the literature.4,5 Lindsell et al. described
the character of alkylstrontium halides in the literature4 as fol-
lows: ‘‘The organostrontium compounds are very reactive sol-
ids, and decompose rapidly in moist atmosphere and slowly in
vacuo at ambient temperature to give some species. The freshly
prepared organostrontium compounds are moderately soluble
in the more polar ethereal solvents, recrystallization being pos-
sible from these solvents.’’ They also reported that alkylstron-
tium halides, prepared with specially treated metallic strontium
and alkyl halides, reacted with carbonyl compounds to afford
the corresponding products in low yields, with the exception
of the reaction with benzophenone.4 We have re-investigated
synthetic reactions using strontium compounds and herein wish
to report the alkylation of aldehydes with alkyl iodides using
metallic strontium, the unusual addition reaction of ethyl ben-
zoate with tert-butyl iodide, and the first example of the reduc-
tion of aldehydes using strontium isopropoxide.
ever, isolation of the product was problematical and the material
balance was inaccurate, possibly because of the volatility of 1-
phenylethanol. Therefore, in order to find the optimum reaction
conditions, we examined the reaction using 2-naphthaldehyde.
When methyl iodide was added to a THF suspension of the al-
dehyde and metallic strontium at ꢁ15 ꢂC (the Barbier-type pro-
cedure), methylation of the aldehyde proceeded smoothly to af-
ford the desired product, in contrast to the Grignard-type proce-
dure. Further, we investigated the Barbier-type procedure under
various reaction conditions at ꢁ15 ꢂC, the results of which are
shown in Table 1. Using slight excesses of methyl iodide and
metallic strontium compared to the amount of aldehyde, the re-
action proceeded smoothly to give the corresponding adduct in
good yields (Entries 4–8). The reactions conditions which gave
the highest yield (Entry 6, Table 1) were assumed to be opti-
mum and were therefore adopted in future experiments.
Next, the scope and versatility of the present reaction were
investigated by using various aldehydes and various alkyl io-
dides. The results are summarized in Table 2. 2-Naphthalde-
hyde reacted with ethyl iodide or butyl iodide instead of methyl
Table 1. Investigation of the Molar Ratio of Methylation
Reagent to 2-Naphthaldehyde
CHO
OH
CH3
CH3I
Sr
-15 °C, THF
Discussion
Entry Aldehyde/mmol MeI/mmol Sr/mmol Yield/%
1
2
3
4
5
6
7
8
1
1
1
1
1
1
1
1
1
1
2
3
1.2
1.3
2
0.5
1
1
1
1.5
2
37
61
51
74
75
82
78
75
First, the alkylation of aldehydes with methyl iodide was ex-
amined under various reaction conditions. When methyl iodide
was reacted with metallic strontium at ꢁ15 ꢂC in THF followed
by the addition of 3-phenylpropanal (the Grignard-type proce-
dure), the methylated compound was obtained in low yield
(vide infra), although the aldehyde disappeared on TLC. Using
benzaldehyde instead of 3-phenylpropanal, the desired product
was obtained in 89% yield by estimation with 1H NMR. How-
2
3
3
Published on the web February 10, 2004; DOI 10.1246/bcsj.77.341

342 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Alkylation Using Metallic Strontium
Table 2. Alkylation of Various Aldehydes by Using Alkyl Iodides in the Presence of Metallic
StrontiumaÞ
R1CHO
R2I
OH
R2
Sr
-15 °C, THF
R1
Entry
1
R1CHO
R2I
CH3I
Yield/%b)
CHO
82
CH3CH2I
2
3
4
5
6
52
45
6
CH3CH2CH2CH2I
(CH3)2CHI
(CH3)3CI
2
CHO
CH3I
88
I
7
8
27c)
43
CH3O
Ph
CHO
CHO
CH3I
CH3I
CH3I
CH3I
9
56
43
49
CH3(CH2)7CHO
10
11
CHO
Ph
a) The reaction was carried out using an aldehyde:an alkyl iodiꢂde:metallic strontium =
1:1.3:2. b) Isolated yield. c) The reaction was carried out at ꢁ20 C. 4-Allylbenzaldehyde
and 1,2-diphenyl-1,2-ethanediol were obtained in 11% and 7% yields, respectively.
iodide to afford the corresponding adducts in moderate to good
sponding allylated alcohol, 1-phenyl-3-buten-1-ol, in 27%
yield (Entry 7). In this case, we investigated the by-products
in detail. As shown in Eq. 1, in addition to 1-phenyl-3-buten-
1-ol, the pinacol coupling product, hydrobenzoin, and 4-allyl-
benzaldehyde were obtained in 11% and 7% yields, respective-
ly. In this reaction, allylation of the carbonyl group of benzal-
dehyde and at the p-position of the aromatic ring of benzalde-
hyde occurred competitively.
yields (Entries 2 or 3). However, as shown in Entries 4 and 5,
the reactions of 2-naphthaldehyde with a sec-alkyl or tert-alkyl
iodide, such as isopropyl iodide or tert-butyl iodide, were slug-
gish and gave the corresponding adducts in low yields (6% or
2%, respectively). Benzaldehyde reacted smoothly with methyl
iodide to afford the methylated product in good yield, but in the
reaction with p-anisaldehyde, the yield decreased (Entries 6 and
8). Using the aliphatic aldehydes, the reactions also proceeded
smoothly to give the desired adducts in moderate to good yields
(Entries 9 and 10), although it is noteworthy that the products
were obtained in low yields when a Grignard-type procedure
was used. ꢀ; ꢁ-Unsaturated aldehydes such as cinnamalde-
hyde predominantly gave the 1,2-addition product (Entry 11).
Lindsell et al. reported that the alkylstrontium halides, prepared
with specially treated metallic strontium and alkyl halides, re-
acted with carbonyl compounds.4 However, they reported that
the reaction proceeded smoothly only with benzophenone to af-
ford the corresponding methylated product in 69% yield, and
that using benzaldehyde the desired product was obtained in
only 21% yield.4 In our method, the reaction of several alkyl
iodides with various aldehydes proceeded smoothly with com-
mercially available metallic strontium to afford the correspond-
ing alkylated products in moderate to good yields.
O
Sr
+
I
H
THF, -20 °C
OH
OH
CHO
+
+
OH
11%
27%
7%
ð1Þ
We were interested in the p-allylated product because this al-
lylation reaction is unusual in these conditions. We tried the re-
action of allyl iodide with various carbonyl compounds or aryl
compounds such as benzaldehyde, phenyl alkyl ketones, benzo-
ic acid, benzoate, benzonitrile, nitrobenzene or chlorobenzene.
Among them, only the reaction of allyl iodide with ethyl ben-
zoate, similar to the reaction of allyl iodide with benzaldehyde,
proceeded to afford the corresponding p-allylated product in
low yield. When we examined a similar reaction using tert-bu-
Benzaldehyde also reacted with methyl iodide to obtain 1-
phenylethanol in very good yield (88%) (Entry 6), although
the reaction of benzaldehyde with allyl iodide gave the corre-

N. Miyoshi et al.
Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
343
O-SrI
CH3
O
H3O+
OH
+
CH3-SrI
Ph
Ph
H
Ph
Ph
Ph
Ph
CH3
H
H
O
Ph
H
O
O-SrI
O
Ph
OH
CH3
Ph
CH3
Ph
H
H
CH3SrI
H3O+
OH
CH3
OSrI
CH3
Ph
CH3
CH2
H
H3O+
CH3
Scheme 1.
tyl iodide, which produces the stable radical species as well as
allyl iodide, a mixture of p-alkylated compound and the 1,6-ad-
duct were obtained in moderate to good yield, although it was
difficult to separate the reaction mixtures. As a result of the in-
vestigation of the reaction conditions, the reaction took place at
ꢁ20 ꢂC, and, in order to purify the crude products, the mixture
was successively oxidized using 2,3-dichloro-5,6-dicyano-1,4-
benzoquinone (DDQ) to afford ethyl 4-tert-butylbenzoate as
the sole product in 55% yield (Eq. 2). There are only a few re-
ports of the p-alkylation of aromatic carbonyl compounds.
Yamamoto et al. reported that the p-alkylation of benzaldehyde
with butyllithium took place using a special sterically bulky
aluminium catalyst.6 Hattori and Miyano reported that the p-al-
kylation of benzoate with butyllithium proceeded using a par-
ticularly sterically bulky ester.7 However, our reaction system
is simpler than the above reactions. Further investigation is
now in progress.
We obtained an unexpected product when we investigated
the methylation of aldehydes. We tried a Grignard-type proce-
dure in which methyl iodide (2.0 molar amounts to the alde-
hyde) was added to a THF suspension of metallic strontium
(2.0 molar amounts to the aldehyde) at room temperature under
an argon atmosphere and, after a 30 min interval, 3-phenyl-
propanal was added to the reaction mixture. The unexpected
dimethylated product, 2-methyl-4-phenyl-2-butanol, was ob-
tained in low yield instead of the desired monomethylated prod-
uct, 4-phenyl-2-butanol (Eq. 3). We were interested in the un-
expected dimethylated product although a number of unidenti-
fied by-products were also obtained. Therefore, we tried some
experiments to find out the mechanism of dimethylation using
benzaldehyde. When methylstrontium iodide, prepared in situ
from 2 molar amounts of methyl iodide and 2 molar amounts
of metallic strontium, was reacted with an equimolar amount
of benzaldehyde, three products, 1-phenylethanol, benzyl alco-
hol, and 2-phenylpropene were obtained in 52%, 20%, and 16%
yields, respectively (Eq. 4).8 However, the dimethylated alco-
hol, 2-phenyl-2-propanol, was not obtained. Based on the
above result, we propose the reaction mechanism shown in
Scheme 1: 1) Methylstrontium iodide reacts with benzaldehyde
to afford the mono-methylated product, 1-phenylethanol. 2)
The Meerwein–Ponndorf–Verley (MPV) type reduction be-
tween strontium 1-phenylethoxide and benzaldehyde occurs
to give acetophenone and benzyl alcohol. 3) Acetophenone re-
acts immediately with the remaining methylstrontium iodide to
produce 2-phenyl-2-propanol. 4) The dimethylated alcohol
changes to 2-phenylpropene because 2-phenyl-2-propanol is
easily dehydrated.
O
I
1.3 mol amt
OEt
+
Sr
1.7 mol amt
THF, -20 °C, 36 h
1.0 mol amt
O
O
ð2Þ
OEt
OEt
+
O
DDQ
PhMe, reflux, 2 h
OEt
55%

344 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Alkylation Using Metallic Strontium
action of ethyl benzoate with tert-butyl iodide proceeds to give
ethyl p-tert-butylbenzoate in moderate to good yield. Under re-
flux conditions in 2-propanol, the Meerwein–Ponndorf–Verley-
type reduction proceeded between aldehydes and strontium iso-
propoxide. To our knowledge, this reduction by strontium alk-
oxide is the first to be reported.
CHO
Ph
OH
CH3
1.0 mol amt
Sr
CH3I
2.0 mol amt
+
Ph
CH3
19% Yield
THF, r.t., 20 h
2.0 mol amt
ð3Þ
O
Experimental
Ph
H
General Methods. 1H NMR spectra were recorded with a
JEOL EX-90A spectrometer and chemical shifts (ꢂ) were reported
in ppm using tetramethylsilane as an internal standard. IR spectra
were obtained using a HORIBA FT-IR 210 spectrometer. Com-
mercially available metallic strontium ingot in liquid paraffin
was cut into small pieces with a cutter in preparation for the start
of each reaction. Tetrahydrofuran was freshly distilled from so-
dium diphenylketyl. Preparative thin layer chromatography
(TLC) was performed on silica gel (Wakogel B-5F). All reagents
were commercially available and used without further purification.
General Procedure for the Methylation of 2-Naphthalde-
hyde Using Metallic Strontium and Methyl Iodide. Under an
argon atmosphere, 2-naphthaldehyde (161 mg, 1.03 mmol), and
methyl iodide (183 mg, 1.29 mmol) were added successively to
a THF (5 mL) suspension of metallic strontium (180 mg, 2.06
mmol) at ꢁ15 ꢂC. After stirring for 7 h, the reaction mixture
was quenched with an aqueous solution of 1 M hydrochloric acid
(10 mL) (1 M = 1 mol dmꢁ3). The organic materials were extract-
ed with diethyl ether (30 mL ꢃ 3), and the combined organic layers
were washed successively with water and brine, and dried over an-
hydrous Na2SO4. After evaporation of the solvent, the residue was
purified by thin layer chromatography on silica gel (hexane:ether =
4:1) to give the corresponding methylated product, 1-(2-naphthyl)-
ethanol (145 mg, 82% yield).
1.0 mol amt
Sr
CH3I
2.0 mol amt
+
2.0 mol amt
THF, r.t., 19 h
ð4Þ
OH
CH3
CH3
+
OH
+
Ph
Ph
Ph
16%
H
20%
52%
In the case of 3-phenylpropanal, the results suggested that an
MPV-type reduction proceeded between the aldehyde and the
strontium alkoxide of the monomethylated adduct, and that
the dimethylated adduct was produced by the methylation of
methyl ketone, 4-phenyl-2-butanone, generated by the above
Oppenauer oxidation. To our knowledge, this is the first report
of a reduction by strontium alkoxide. Although the reaction
mechanism is not clear; it is also presumed that strontium hy-
dride, generated by the strontium alkoxide, reduced the alde-
hyde.9
These results prompted us to examine the MPV-type reduc-
tion of 2-naphthaldehyde with strontium alkoxide. 2-Naphthal-
dehyde reacted with strontium isopropoxide in THF under re-
flux condition to give the reduced product in only 6% yield
(Eq. 5). However, when the solvent was changed to 2-propanol,
the reaction of 2-naphthaldehyde with strontium isopropoxide
proceeded smoothly under reflux conditions to afford the corre-
sponding product in good yield (Table 3). Thus, we were able to
decrease the amount of strontium isopropoxide to 0.5 the molar
amount compared to an equimolar amount of aldehyde and still
obtain the desired product in 67% yield (Entry 1 in Table 3).
1H NMR (90 MHz, CDCl3) ꢂ 1.5 (3H, d, J ¼ 6:4 Hz), 2.2 (1H,
brs), 5.0 (1H, q, J ¼ 6:4 Hz), 7.4–7.8 (7H, m). IR (neat) 3318,
2969, 2923, 2605, 1363, 1124, 1074 cmꢁ1. This product was iden-
tified by comparison with an authentic sample prepared from a
known procedure.10
The spectral data of the products were as follows.
1-(2-Naphthyl)-1-propanol. 1H NMR (90 MHz, CDCl3) ꢂ 0.9
(3H, t, J ¼ 7:3 Hz), 1.8 (2H, quint, J ¼ 7:2 Hz), 2.1 (1H, brs), 4.7
(1H, t, J ¼ 6:3 Hz), 7.2–7.9 (7H, m). IR (neat) 3375, 3055, 2964,
2931, 2875, 1455, 1271, 1126, 1018, 856, 820, 748 cmꢁ1. This
product was identified by comparison with an authentic sample
prepared from a known procedure.10
1-(2-Naphthyl)-1-pentanol. 1H NMR (90 MHz, CDCl3) ꢂ 0.9
(3H, brm), 1.3 (2H, brm), 1.7–1.8 (4H, m), 2.1 (1H, brs), 4.8 (1H, t,
J ¼ 6:5 Hz), 7.4–7.8 (7H, m). IR (neat) 3375, 3054, 2931, 1602,
1465, 1270, 1126, 1043, 819, 746 cmꢁ1. This product was identi-
fied by comparison with an authentic sample prepared from a
known procedure.10
Sr(OiPr)2
CHO
OH
1.0 mol amt
THF, reflux, 7 h
1.0 mol amt
6% Yield
ð5Þ
In summary, in the presence of metallic strontium, the Barb-
ier-type alkylation of aldehydes with alkyl iodides proceeds
ꢂ
smoothly at ꢁ15 C under an argon atmosphere to afford the
corresponding alkylated alcohols, and the unusual addition re-
1-Phenylethanol. This product was identified by comparison
with an authentic sample.11
1-(4-Methoxyphenyl)ethanol. This product was identified by
comparison with the literature.12
4-Phenyl-2-butanol. This product was identified by compari-
son with an authentic sample.11
Table 3. The Reduction of 2-Naphthaldehyde Using Stron-
tium Diisopropoxide
Sr(OiPr)2
CHO
OH
iPrOH, reflux, 4 h
2-Dodecanol. This product was identified by comparison with
the literature.12
4-Phenyl-3-buten-2-ol. This product was identified by com-
parison with the literature.12
General Procedure for the p-Alkylation of Ethyl Benzoate
Entry
Sr(OiPr)2/mol amt
Yield/%
1
2
3
0.5
1.0
2.0
67
75
66

N. Miyoshi et al.
Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
345
Using tert-Butyl Iodide and for the Oxidation of the Resulting
Mixture of the p-Butylated Product and 1,6-Adduct. Under
an argon atmosphere, ethyl benzoate (362 mg, 2.41 mmol) was
added to a THF (10 mL) suspension of metallic strontium (355
mg, 4.05 mmol) at ꢁ20 ꢂC, followed by tert-butyl iodide (579
mg, 3.15 mmol). After stirring for 36 h, the reaction mixture was
quenched with 1 M hydrochloric acid (10 mL). The organic mate-
rials were extracted with diethyl ether (30 mL ꢃ 3), and the com-
bined organic layers were washed successively with water and
brine, and dried over anhydrous Na2SO4. After evaporation of
the solvent, the residue was reacted with 2,3-dichloro-5,6-dicya-
no-1,4-benzoquinone (453 mg, 1.99 mmol) in toluene (15 mL) un-
der reflux conditions. After stirring for 2 h, the reaction mixture
was quenched with water (10 mL). The organic materials were ex-
tracted with diethyl ether (30 mL ꢃ 3), and the combined organic
layers were washed successively with water and brine, and dried
over anhydrous Na2SO4. After evaporation of the solvent, the res-
idue was purified by thin layer chromatography on silica gel (hex-
ane:ether = 60:1) to give the corresponding tert-butylated product,
ethyl 4-tert-butylbenzoate (274 mg, 55% yield). This product was
identified by comparison with an authentic sample.11
References
N. A. Bell and W. E. Lindsell, ‘‘Beryllium Magnesium,
Calcium, Strontium and Barium’’ in ‘‘Comprehensive Organome-
tallic Chemistry,’’ ed by G. Wilkinson, F. G. A. Stone, and E. W.
Abel, Pergamon Press, Oxford (1982), Vol. 1, Chaps. 3 and 4,
pp. 121–252, and references cited therein.
1
2
For the synthesis of alkylcalcium halide and the reaction
using Rieke calcium, see: a) K. Mochida, S. Ogura, and T.
Yamanishi, Bull. Chem. Soc. Jpn., 59, 2633 (1986). b) T. Wu, H.
Xiong, and R. D. Rieke, J. Org. Chem., 55, 5045 (1990). c) R.
A. O’Brien, T. Chen, and R. B. Rieke, J. Org. Chem., 57, 2667
(1992). For the reaction using Rieke barium, see: d) A.
Yanagisawa, S. Habaue, and H. Yamamoto, J. Am. Chem. Soc.,
113, 8955 (1991). e) A. Yanagisawa, S. Habaue, K. Yasue, and
H. Yamamoto, J. Am. Chem. Soc., 116, 6130 (1994).
3
B. J. Wakefield, ‘‘Organomagnesium Methods in Organic
Synthesis,’’ Academic Press, UK (1995).
a) G. Gowenlock, W. E. Lindsell, and B. Singh, J. Organo-
4
met. Chem., 101, C37 (1975). b) G. Gowenlock, W. E. Lindsell,
and B. Singh, J. Chem. Soc., Dalton Trans., 1978, 657.
5
a) M. S. Sell and R. D. Rieke, Synth. Commun., 25, 4107
General Procedure for the Meerwein–Ponndorf–Verley-
Type Reduction of 2-Naphthaldehyde Using Strontium
Isopropoxide. Under an argon atmosphere, to a solution of stron-
tium isopropoxide (124 mg, 0.604 mmol) in 2-propanol (5 mL) at
room temperature was added 2-naphthaldehyde (91 mg, 0.585
mmol). After stirring for 4 h under reflux conditions, the reaction
mixture was quenched with an aqueous solution of 1 M hydro-
chloric acid (10 mL). The organic materials were extracted with di-
ethyl ether (30 mL ꢃ 3), and the combined organic layers were
washed successively with water and brine, and dried over MgSO4.
After evaporation of solvent, the residue was purified by thin layer
chromatography on silica gel (hexane:ether = 4:1) to give the cor-
responding methylated product, 2-naphthylmethanol (72 mg, 75%
yield). This product was identified by comparison with an authen-
tic sample.11
(1995). b) L. N. Cherkasov, V. I. Panov, and V. N. Cherkasov,
Russ. J. Org. Chem., 29, 411 (1993). c) L. N. Cherkasov and S.
I. Radchenko, Russ. J. Org. Chem., 30, 456 (1994). d) L. N.
Cherkasov and V. N. Cherkasov, Russ. J. Org. Chem., 31, 267
(1995).
6 K. Maruoka, M. Ito, and H. Yamamoto, J. Am. Chem. Soc.,
117, 9091 (1995).
7 T. Hattori, N. Koite, T. Satoh, and S. Miyano, Tetrahedron
Lett., 36, 4821 (1995).
8
Lindsell et al. have reported that methylstrontium iodide
reacted with benzaldehyde to obtain 2-phenylpropene in only 2%
yield. However, a reaction mechanism was not given.
9
We understand that strontium hydride was commercially
available from Aldrich Inc. until a few years ago, but is not offered
at the present time. To our knowledge, there is no report in the
literature regarding reduction using strontium hydride.
We thank the Center for Cooperative Research, The Univer-
sity of Tokushima, for the measurement of 400 MHz 1H NMR
spectra. The present work was partially supported by a Grant-
in-Aid from the Ministry of Education, Culture, Sports, Science
and Technology (N. M.).
10 D. M. Huryn, ‘‘Carbanions of Alkaki and Alkaline Earth
Cations: (ii) Selectivity of Carbonyl Addition Reaction’’ in ‘‘Com-
prehensive Organic Synthesis,’’ ed by B. M. Trost, Pergamon
Press, Oxford (1991), Vol. 1, Chap. 1.2, pp. 49–75.
11 These products are commercially available.
12 C. J. Pouchert and J. R. Campbell, ‘‘The Aldrich Library of
NMR Spectra,’’ Aldrich Chemical Co. Inc., Wisconsin (1974).