Carbonyllithium chemistry. Intramolecular conversion of an acyllithium via the utilization of an anionic 1,2-stannyl rearrangement

Article abstract of DOI:10.1016/S0022-328X(98)00936-X

The reaction of α-stannylmethyllithium with CO (1 atm) generates the acyllithium that smoothly undergoes anionic 1,2-stannyl rearrangement at -78°C to give the enolate derivative of acyltin. The rearrangement of the stannyl group is much faster than that

Full text of DOI:10.1016/S0022-328X(98)00936-X

Journal of Organometallic Chemistry 574 (1999) 171–175
Carbonyllithium chemistry. Intramolecular conversion of an
acyllithium via the utilization of an anionic 1,2-stannyl rearrangementꢀ
Keiji Iwamoto, Naoto Chatani, Shinji Murai *
Department of Applied Chemistry, Faculty of Engineering, Osaka Uni6ersity, Suita, Osaka 565-0871, Japan
Received 7 July 1998; received in revised form 28 August 1998
Abstract
The reaction of h-stannylmethyllithium with CO (1 atm) generates the acyllithium that smoothly undergoes anionic 1,2-stannyl
rearrangement at −78°C to give the enolate derivative of acyltin. The rearrangement of the stannyl group is much faster than
that of the silyl group. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Acyllithium; Intramolecular conversion; h-Stannylmethyllithium; Carbon monoxide; Anionic 1,2-stannyl rearrange-
ment
1. Introduction
with carbon monoxide gave an acyllithium derivative
that then underwent an anionic 1,2-silicon shift [3a]. The
intramolecular process allowed the conversion of the
highly reactive acyllithium into the more stable lithium
enolate of trimethylsilyl methyl ketone. This 1,2-anionic
silicon shift was observed only at temperatures above
15°C. At lower temperatures, e.g. at −78°C, a different
product was formed, which corresponded to a dimer of
the acyllithium.
It would be interesting to determine if an analogous
conversion is possible in the case of organotin com-
pounds. No distinct example of an anionic 1,2-migration
of an organostannyl group is known, to the authors
knowledge. The anionic rearrangement of an organos-
tannyl group would be expected to be much faster than
that of an organosilyl group, since it has been firmly
established that lithium–tin exchange is much faster than
lithium–silicon exchange [5]. It should also be noted that
such lithium–metal exchange constitutes a nucleophilic
displacement at the tin or silicon atom and can be
regarded as an anionic rearrangement in the case of an
intramolecular process. This paper reports that the
reaction of (tributylstannyl)methyllithium, Bu3SnCH2Li,
with carbon monoxide proceeds in a highly selective
manner due to the rapid 1,2-stannyl migration, even at
−78°C.
It is well known that the reaction of organolithium
compounds with carbon monoxide generates carbonyl-
lithium derivatives 1 as initial intermediates (see Eq. (1)).
In general, carbonyllithium intermediates are too reac-
tive to undergo selective reactions. Seyferth [1] and others
[2] have demonstrated that it is possible to trap the highly
reactive carbonyllithium 1 by an electrophile, providing
the trapping reagents are present in situ. The authors
have devised a different methodology, i.e. intramolecular
trapping, for the immediate conversion of carbonyl-
lithium species into more stable ones, such as enolates [3]
and ynolates [4].
(1)
In a previous paper, the authors reported that the
reaction of trimethylsilylmethyllithium, Me3SiCH2Li,
ꢀ This paper is dedicated to the memory of the late Professor
Rokuro Okawara.
* Corresponding author. Fax: +81-6-879-7396.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00936-X

172
K. Iwamoto et al. / Journal of Organometallic Chemistry 574 (1999) 171–175
a silyl group does not migrate at −78°C and the
reaction gives an enediol compound [3a]. These results
indicate that the migration of the stannyl group is
considerably faster than that of the silyl group.
The reaction of 1-(tributylstannyl)propyllithium [8]
with CO at −78°C also led to a clean reaction involv-
ing intramolecular conversion of the acyllithium via
1,2-stannyl shift (see Eq. (2)).
Scheme 1.
2. Results and discussion
(2)
For the generation of h-stannylmethyllithiums, two
methods involving lithium–iodine exchange and
lithium–tin exchange, reported by Kaufmann [6] and
Sato [7], respectively, have been shown to be useful.
Because of the efficiency and ready availability of start-
ing materials, the method described by Kaufmann was
adopted. However, the n-BuLi used in this method
gives rise to n-BuI as a by-product, which may further
react and thus complicate the reaction. For this reason,
the authors modified Kaufmann’s method and used two
equivalents of t-BuLi instead of one.
The reaction was carried out as follows (see Section 3
for details). To an Et2O solution of tributylstannyl-
methyl iodide, 2, a pentane solution of t-BuLi (2.2
equivalents) was added at −50°C. The mixture was
exposed to carbon monoxide at atmospheric pressure at
−78°C for 2 h. After quenching with triethylsilyl trifl-
uoromethanesulfonate (1.1 equivalents) at −78°C, the
reaction mixture was stirred at 20°C for 12 h. After
work-up with cold sat. NaHCO3 (aq), triethyl[[1-(trib-
utylstannyl)ethenyl]oxy]silane (7) was isolated in 88%
yield by Kugelrohr distillation (153°C/1 mmHg).
The reaction sequence envisaged is shown in Scheme
1. This intramolecular transformation of acyllithium 4
takes place via the anionic 1,2-shift of the organotin
group. It is noteworthy that the stannyl group migrates
smoothly, even at −78°C. In contrast, it is known that
As observed in the reaction of silylmethyllithium with
CO, this reaction also gave a more stable E-enolate,
predominantly [3a,e]. The ratio of the stereochemistry
of the silylated product 9 was determined by H-NMR
of vinylic hydrogens [9].
1
The enolate appears to undergo standard enolate
reactions. The reaction of the lithium enolate of acyltin
with electrophiles would be expected to give acyltin
compounds, which are known to be somewhat difficult
to handle because of their lability [10]. The reaction of
acyltin enolate with two equivalents of an aldehyde was
examined. Reaction with benzaldehyde afforded the
anti-1,3-diol monoester by the aldol-Tishchenko reac-
tion [11].
An acyltin enolate 6 was treated with two equivalents
of RCHO (R=Ph or i-Pr) at 20°C for 12 h. After
quenching with sat. NH4Cl (aq), the anti-1,3-diol mo-
noester 14 was isolated by column chromatography on
silica gel (14a, 71%; 14b, 69%; Scheme 2). The stereo-
chemistries of the products 14 were determined by
comparison with similar compounds [12]. Excellent
diastereoselection would be expected to proceed via the
formation of a six-membered transition state for the
case of an intramolecular Tishchenko reduction (Fig. 1)
Scheme 2.

K. Iwamoto et al. / Journal of Organometallic Chemistry 574 (1999) 171–175
173
column packed with anhydrous calcium sulfate. After
two cycles of evacuation of the nitrogen and filling with
carbon monoxide, the reaction mixture was stirred un-
der this atmosphere of carbon monoxide for 2 h. To the
reaction mixture was added 0.497 ml (2.2 mmol) of
triethylsilyl trifluoromethanesulfonate at −78°C and
the reaction mixture was allowed warm to 20°C, and
then stirred for 12 h. To the mixture, 10 ml of a cold
sat. NaHCO3 (aq) and 30 ml of ether were added, and
the layers were separated. The aqueous layer was ex-
tracted with ether (3×15 ml). The organic layers were
combined and dried over magnesium sulfate. The sol-
vents were removed under reduced pressure to provide
a yellow liquid. Kugelrohr distillation (153°C/1 mmHg)
of the residue gave pure product 7 as a colorless liquid
(0.785 g, 88% yield). 1H-NMR (CDCl3) l 0.67 (q,
J=8.3 Hz, 6H, SiCH2), 0.75–1.05 (m, 24H, SiCH2CH3
and SnCH2CH2CH2CH3), 1.2–1.65 (m, 12H,
SnCH2CH2CH2), 4.23 [s, J(1H–119Sn)=27 Hz, 1H,
(Z)-CH2ꢀC], 4.89 [s, J(1H–119Sn)=103 Hz, 1H, (E)-
CH2ꢀC]; 13C-NMR (CDCl3) l 5.32 (SiCH2), 6.76
(SiCH2C), 9.85 [J(13C–119Sn)=336 Hz, J(13C–
117Sn)=321 Hz, SnCH2], 13.70 (SnCH2CH2CH2C),
27.33 [J(13C–119Sn)=56 Hz, SnCH2CH2C], 29.02
[J(13C–119Sn)=21 Hz, SnCH2C], 105.28 [J(13C–
119Sn)=94 Hz, SnCꢀCH2], 169.67 (SnCꢀCH2); IR
(neat) 2960 (s), 1578 (s), 1466 (s), 1417 (m), 1377 (m),
1238 (m), 1173 (s), 1071 (w), 1002 (s), 825 (m), 748 (s),
664 (w) cm−1; MS m/z (relative intensity) 391 (10,
M+-Bu), 365 (12), 309 (23), 307 (13), 305 (10), 253 (17),
251 (16), 249 (13), 234 (11), 223 (18), 221 (15),195 (15),
193 (12), 179 (18), 177 (22), 175 (16), 123 (11), 121 (26),
120 (12), 119 (18), 117 (11), 115 (16), 87 (62), 59 (100),
58 (10), 57 (17). Anal. Calc. for C29H44OSiSn: C, 53.70;
H, 9.91. Found: C, 53.65; H, 9.79.
Fig. 1. The six-membered transition state for the case of an in-
tramolecular Tishchenko reduction.
[11a,c,e,g–i]. The following intramolecular transfer of
the benzoyl group (12“13) gives the observed product
14 [11b,f,g].
The authors have thus demonstrated that the anionic
rearrangement of an organostannyl group in the acyl-
lithium occurred rapidly, even at low temperature (−
78°C). To their knowledge, this is a rare example of a
1,2-anionic stannyl rearrangement. The present work,
in addition to the one previously reported, indicates
that the rearrangement is a key step in the intramolecu-
lar conversion of carbonyllithium and should find fur-
ther applications.
3. Experimental
1H-NMR and 13C-NMR spectra were recorded on a
JEOL JNM-EX270 (1H at 270 MHz, 13C at 67.5 MHz)
spectrometer. Mass spectra (MS) were recorded on a
Shimadzu GCMS-QP5000 spectrometer. Infrared spec-
tra (IR) were recorded on a Hitachi 270-50 IR spec-
trometer as neat. Column chromatography was
performed using Kiesegel 60 (230–400 mesh, Merck
9385) Diethyl ether (Et2O) was distilled from sodium
benzophenone ketyl immediately prior to use. A 1.54 M
pentane solution of t-BuLi was purchased from Kanto
Chemical Company, and used without titration. Trib-
utylstannylmethyl iodide 2 [13] and 1-(tributylstan-
nyl)propyl iodide 8 [8] were prepared according to
literature procedures.
3.2. Synthesis of triethyl[[1-(tributylstannyl)butenyl]
oxy]silane (9)
In a manner similar to that described for the tin
compound 2, 0.918 g (2.0 mmol) of 8 in 20 ml of Et2O
was reacted with t-BuLi (1.54 M in pentane, 4.4 mmol,
2.86 ml) at −50°C and CO at −78°C, triethylsilyl
trifluoromethanesulfonate (2.2 mmol) at −78°C fol-
lowed by stirring at 20°C for 12 h. After work-up and
purification by Kugelrohr distillation (160–165°C/0.75
mmHg) of the product mixture gave the acyltin enolate
9 as a colorless liquid (0.853 g, 88% yield, E/Z=92/8).
Spectral data were obtained from a mixture of E- and
Z-isomers. In the 13C-NMR spectrum of the mixture of
E- and Z-isomers, the resonances arising from the
3.1. Synthesis of triethyl[[1-(tributylstannyl)ethenyl]
oxy]silane (7)
A 50-ml round-bottomed flask equipped with a mag-
netic stirrer bar, a three-way stopcock, and a nitrogen
line was flame-dried under a stream of nitrogen. In the
reaction flask, 20 ml of anhydrous Et2O and 0.862 g
(2.0 mmol) of tributylstannylmethyl iodide 2 were
placed and the solution was cooled to −50°C with a
dry ice/CH3CN bath. To the stirred solution, 2.86 ml of
a pentane solution of t-BuLi (1.54 M, 4.4 mmol) were
added by a syringe within 5 s. After stirring for 10 min,
the reaction mixture was cooled to −78°C with a dry
ice/MeOH bath. The three-way stopcock was then con-
nected to a vacuum line (10 mmHg) and also to a
balloon filled with carbon monoxide through a glass
1
Z-isomer could not be observed. H-NMR (CDCl3) l
(E-isomer) 0.66 (q, J=7.9 Hz, 6H, SiCH2), 0.80–1.05
(m, 27H, SiCH2CH3 and SnCH2CH2CH2CH3 and
CꢀCHCH2CH3), 1.20–1.60 (m, 12H, SnCH2CH2CH2),
2.13 (qn, J=7.3 Hz, 2H, CꢀCHCH2), 4.61 (t, J=6.6

174
K. Iwamoto et al. / Journal of Organometallic Chemistry 574 (1999) 171–175
Hz, 1H, CꢀCH), (Z-isomer) (partial) 1.8 (qn, J=7.8
Hz, CꢀCHCH2), 5.47 (t, J=7.8 Hz, CꢀCH); 13C-NMR
(CDCl3) (E-isomer) 5.36 (SiC), 6.92 (SiCH2C), 10.12
[J(13C–119Sn)=331 Hz, J(13C–117Sn)=316 Hz,
SnCH2], 13.66 (SnCH2CH2CH2C), 14.32 (CꢀCHCH2
CH3), 18.64 (CꢀCHCH2), 27.39 [J(13C–119Sn)=57 Hz,
SnCH2CH2C], 29.00 [J(13C–119Sn)=18 Hz, SnCH2C],
129.61 (SnCꢀCH), 156.53 (SnCꢀCH); IR (neat) (mix-
ture of E- and Z-isomers) 2960 (s), 2930 (s), 2878 (s),
1605 (m), 1463 (s), 1417 (m), 1377 (m), 1326 (m), 1283
(m), 1238 (m), 1136 (s), 1073 (s) 1004 (s), 961 (m), 900
(w), 875 (w), 838 (m), 768 (m), 741 (s) cm−1; MS
m/z (relative intensity) 419 (11, M+-Bu), 365 (13), 309
(26), 308 (10), 305 (10), 253 (14), 251 (20), 249 (12), 223
(23), 221 (18), 195 (22), 193 (16), 191 (11), 179 (20), 177
(23), 175 (13), 165 (12), 149 (11), 123 (14), 121 (31), 120
(16), 119 (28), 117 (17), 115 (21), 91 (16), 87 (70), 75
(16), 69 (10), 59 (100), 58 (14), 57 (31), 56 (10), 55 (14).
Anal. (mixture of E- and Z-isomers) Calc. for
C22H48OSiSn: C, 55.58; H, 10.18. Found: C, 55.42; H,
10.08.
1420 (m), 1376 (m), 1315 (s), 1265 (s), 1198 (w), 1174
(m), 1115 (s), 1068 (s), 1046 (m), 1025 (s), 998 (m), 961
(w), 912 (w), 875 (w), 844 (w), 805 (w), 757 (m), 712 (s)
cm−1; MS m/z (relative intensity) 545 (M+, 0.44), 489
(18), 487 (15), 179 (26), 177 (28), 176 (10), 175 (18), 123
(13), 121 (31), 120 (14), 119 (23), 118 (15), 117 (71), 115
(12), 105 (100), 79 (17), 77 (59), 51 (18). Anal. Calc. for
C28H42O3Sn: C, 61.67; H, 7.76. Found: C, 61.78; H,
7.64.
3.4. Reaction of acyltin enolate 6 with two equi6alents
of isobutyraldehyde (14b)
To a diethyl ether solution of acyltin enolate 6,
prepared from (tributylstannyl)methyllithium 3 with
CO vide supra, 0.317 g (4.4 mmol) of isobutyraldehyde
were added at −78°C and the mixture was stirred at
20°C for 12 h. The mixture was then quenched with 10
ml of sat. NH4Cl (aq), 30 ml of Et2O were added, and
the layers were separated. The aqueous layer was ex-
tracted with ether (3×15 ml). The combined organic
layers were dried over anhydrous magnesium sulfate
and concentrated under reduced pressure to afford a
yellow oil. The residue was subjected to column chro-
matography on silica gel using hexane/EtOAc=9/1
as the eluent (Rf=0.20) to give 14b as a colorless
3.3. Reaction of acyltin enolate 6 with two equi6alents
of benzaldehyde (14a)
To a diethyl ether solution of acyltin enolate 6,
prepared from (tributylstannyl)methyllithium 3 with
CO vide supra, 0.467 g (4.4 mmol) of benzaldehyde at
−78°C were added and the mixture was stirred at 20°C
for 12 h. The mixture was then quenched with 10 ml of
sat. NH4Cl (aq), 30 ml of Et2O were added, and the
layers were separated. The aqueous layer was extracted
with ether (3×15 ml). The combined organic layers
were dried over anhydrous magnesium sulfate and con-
centrated under reduced pressure to afford a yellow oil.
The residue was subjected to column chromatography
on silica gel using hexane/EtOAc=7/1 as the eluent
(Rf=0.26) to give 14a as a colorless oil (0.780 g, 71%
yield). 1H-NMR (CDCl3) l 0.85 (t, J=7.3 Hz, 9H,
CH3), 0.92–1.56 (m, 18H, SnCH2CH2CH2), 2.03 (ddd,
J=3.0 Hz, 10.2 Hz, 14.9 Hz, 1H, CHH), 2.40 (ddd,
J=2.6 Hz, 12.5 Hz, 14.9 Hz, 1H, CHH), 3.09 (d,
J=3.6 Hz, 1H, OH), 4.69 (ddd, J=3.0 Hz, 3.6 Hz,
10.2 Hz, 1H, PhCH), 5.56 (dd, J=2.6 Hz, 12.5 Hz, 1H,
SnCH), 7.20–7.60 (m, 8H, Ar-H), 8.01 (d, J=7.6 Hz,
2H, Ar-H); 13C-NMR (CDCl3) l 9.44 [J(13C–119Sn)=
325 Hz, J(13C–117Sn)=310 Hz, SnCH2], 13.59
(SnCH2CH2CH2C), 27.33 [J(13C–119Sn)=56 Hz,
SnCH2CH2C], 28.97 [J(13C–119Sn)=20 Hz, SnCH2C],
44.36 (CH2), 67.60 [J(13C–119Sn)=337 Hz, J(13C–
117Sn)=322 Hz, SnCHOH], 70.66 [J(13C–119Sn)=39
Hz, PhCH], 125.61 (Ar), 127.22 (Ar), 128.34 (Ar),
128.37 (Ar), 129.45 (Ar), 130.21 (Ar), 132.85 (Ar),
144.35 (Ar), 167.87 (CꢀO); IR (neat) 3486 (br), 3066
(w),3032 (w), 2960 (s), 2928 (s), 2874 (s), 2854 (s), 1699
(s), 1604 (w), 1585 (w), 1542 (w), 1495 (w), 1454 (s),
1
oil (0.608 g, 69% yield). H-NMR (CDCl3) l 0.75–1.05
[m, 21H, (CH3)2CHO and SnCH2CH2CH2CH3], 1.16
[dd, J=1.3 Hz, 6.9 Hz, 6H, (CH3)2CHCꢀO], 1.20–1.75
[m, 14H, (CH3)2CHCꢀO and SnCH2CH2CH2], 2.02
(ddd, J=2.6 Hz, 12.2 Hz, 14.2 Hz, 1H, CHH),
2.55 (hept, J=6.9 Hz, 1H, CHCꢀO), 2.64 (d, J=4.0
Hz, 1H, OH), 3.15–3.25 (m, 1H, i-PrCHOH), 5.19
(dd, J=2.6 Hz, 12.2 Hz, 1H, SnCHO); 13C-NMR
(CDCl3)
l
9.19 [J(13C–119Sn)=325 Hz, J(13C–
117Sn)=310 Hz, SnCH2], 13.59 (SnCH2CH2CH2C),
17.79 (CH3CHCHOH), 18.76 (CH3CHCHOH), 19.09
(CH3CHCꢀO), 19.19 (CH3CHCꢀO), 27.35 [J(13C–
119Sn)=55 Hz, SnCH2CH2C], 28.95 [J(13C–119Sn)=21
Hz, SnCH2C], 33.43 (CHCHOH), 34.27 (CHCꢀO),
38.65 (CH2CHOH), 66.74 [J(13C–119Sn)=354 Hz,
J(13C–117Sn)=337 Hz, SnCHO], 72.53 [J(13C–
119Sn)=38 Hz, i-PrCHOH], 178.44 (CꢀO); IR (neat)
3506 (br), 2962 (s), 2932 (s), 2876 (s), 2856 (s), 1714 (s),
1469 (s), 1420 (m), 1387 (m), 1377 (m), 1340 (m), 1290
(m), 1256 (m), 1197 (s), 1161 (s), 1071 (m), 1041 (m),
998 (m), 961 (m), 877 (m), 765 (w) cm−1; MS m/s
(relative intensity) 477 (1.0, M+), 425 (16), 423 (13),
422 (18), 421 (93), 420 (37), 419 (76), 418 (26), 417 (40),
321 (31), 319 (19), 317 (12), 235 (25), 233 (29), 231 (18),
207 (50), 206 (13), 205 (40), 204 (16), 203 (27), 183 (14),
181 (15), 179 (82), 178 (28), 177 (100), 176 (34), 175
(68), 174 (13), 173 (21), 149 (15), 147 (16), 145 (10), 137
(48), 136 (14), 135 (44), 134 (13), 133 (28), 125 (18), 123
(38), 122 (11), 121 (96), 120 (43), 119 (73), 118 (33), 117
(38), 116 (12), 99 (23), 81 (14), 73 (19), 71 (71), 57 (41),

K. Iwamoto et al. / Journal of Organometallic Chemistry 574 (1999) 171–175
175
[5] P.G. Harrison, Chemistry of Tin, Blackie, Glasgow, 1989.
56 (16), 55 (92). Anal. Calc. for C22H46O3Sn: C, 55.36;
H, 9.71. Found: C, 55.35; H, 9.54.
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Acknowledgements
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This work is partially supported by grants from the
Ministry of Education, Science, Sports and Culture,
Japan.
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