Quantitative data on the effects of alkyl substituents and Li-O and Li-N chelation on the stability of secondary a-oxy-organolithium compounds

Article abstract of DOI:10.1002/chem.200600864

A ΔG_eq stability scale of secondary a-oxy-organolithium compounds was established from measurements of tin-lithium exchange equilibria in THF, and the quantitative effects of substituents at the anionic center on carbanion stability are present

Full text of DOI:10.1002/chem.200600864

FULL PAPER
DOI: 10.1002/chem.200600864
Quantitative Data on the Effects of Alkyl Substituents and Li–O and Li–N
Chelation on the Stability of Secondary a-Oxy-Organolithium Compounds
Pablo Monje, Paula GraÇa, M. Rita Paleo, and F. Javier Sardina*[a]
Abstract: A DGeq stability scale of sec-
ondary a-oxy-organolithium com-
bility of organolithium compounds
when attached to the carbon bearing
the negative charge, but the extent of
this effect is highly dependent on the
nature of the rest of the substituents at-
tached to the anionic center. Quantita-
tive data on the stabilization imparted
to organolithium compounds by Li–O
and Li–N chelation have been deter-
mined for a variety of systems. The for-
mation of four- and five-membered
chelate rings leads to a considerable
stabilization of the organolithium com-
pound, while chelation through the for-
mation of six-membered rings affords
no extra stabilization to this type of or-
ganometallics. Multinuclear NMR ex-
periments carried out on several a-oxy-
organolithium compounds to determine
their aggregation state are supportive
of these species being monomers in
THF solution.
pounds was established from measure-
ments of tin–lithium exchange equili-
bria in THF, and the quantitative ef-
fects of substituents at the anionic
center on carbanion stability are pre-
sented. A new lead–lithium exchange
equilibrium reaction was also investi-
gated and shown to be a very useful al-
ternative for the determination of the
relative stability of the more sterically
hindered organolithium compounds.
Alkyl groups adversely affect the sta-
Keywords: aggregation · chelates ·
lithium · NMR spectroscopy
Introduction
to the more basic, highly functionalized, more synthetically
useful organolithium reagents is problematic, especially in
ethereal solvents, despite of the fact that Streitwieser[4] has
provided data for several types of aromatic, heteroaromatic,
and benzylic systems, obtained using this method.
Organolithium reagents play a central role in organic syn-
thesis and the factors governing their structure, stability and
reactivity have been the object of very active study for deca-
des.[1] A particularly interesting aspect of the chemistry of
this type of compounds is how substituents (both proximate
and remote to the carbanionic center) influence the stability
of these organolithium species. Quantitative data on this
fundamental question is still lacking for the most part, due
to the difficulty of establishing a general quantitative ther-
modynamic stability scale of organolithium compounds.[2]
Traditionally, the stabilities of organolithium compounds
have been determined by measuring the pK of the corre-
sponding carbanions,[3] but the application of this approach
We have recently reported the measurement of the rela-
tive stabilities of a-heterosubstituted-benzylic organolithium
compounds in tetrahydrofuran, thus providing for the first
time quantitative data on the effects of the heteroatom adja-
cent to the carbanionic center, as well as those of the heter-
oatomꢀs substituents, on the stabilities of these type of
highly functionalized organometallics.[2] Our approach is
based on the establishment of a Sn–Li exchange between
the organolithium under study and a reference compound
(as shown in Equation (1) (see below), an equilibrium reac-
tion which favors the pairing of the most stable carbanion
with the more electropositive Li atom.[5,6] We report herein
the improvement of this Sn–Li exchange equilibrium
method, its application to the determination of the stabilities
of a more comprehensive set of organolithium compounds,
and the determination of the quantitative effects of substitu-
ents on the stability of these types of functionalized organo-
metallics. We have chosen THF as the solvent for our stud-
ies since most of the synthetic applications of organolithium
compounds are carried out in THF solutions.
[a] P. Monje, Dr. P. GraÇa, Dr. M. R. Paleo, Prof. Dr. F. J. Sardina
Departamento de Química Orgµnica, Facultad de Química
Universidad de Santiago de Compostela
15782 Santiago de Compostela (Spain)
Fax: ( +34)81-595-012
E-mail: qojskd@usc.es
Supporting information for this article is available on the WWW
under http://www.chemistry.org or from the author.
Chem. Eur. J. 2007, 13, 2277 – 2289
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2277

Results and Discussion
species, which are present in the equilibria at undetectably
low concentrations (except in very specific cases, such as
diaryl- or polyarylated stannanes in THF/HMPA solu-
tions).[9] Since we did not detect in the 119Sn NMR spectra of
the equilibrium mixtures signals at the chemical shift expect-
ed for the pentacoordinated stannates (around d ꢀ280 ppm)
we have ruled out the possibility that these species play a
significant role in determining the ratios of the products ob-
tained after protonation, and thus that the measured ratios
represent the true organolithium and stannane concentra-
tions at equilibrium in each case.
Our data were coincident with those obtained from Fras-
erꢀs pK values except for the case of 2-lithium-N-methylin-
dole (3b), which under our experimental conditions was
shown to be 0.9 kcalmolꢀ1 more stable than 2-lithium-N,N-
dimethylaminopyrrole (2b), which suggest an apparent pK
of 36.1 for the parent heterocycle, two units lower than the
reported value.[7e] A possible explanation of this discrepancy
is that the equilibrium point had not been reached under
Fraserꢀs conditions as N-methylindole possesses no donor
substituents which would accelerate the rate of deprotona-
tion by coordination with the base, as anisole and dimethy-
laminopyrrole do. It must be pointed out that under thermo-
dynamic conditions the rate of a-lithiation in five-membered
heterocycles follows the order sulfur>oxygen>N-alkyl.[10]
Having established that our Sn–Li exchange method was
indeed providing stability data coincident with those derived
from pK measurements we undertook a more detailed study
of the factors that affect the stability of a-oxy-organolithium
compounds. A range of organolithium compounds (7, 11,
13) and their stannylated precursors (8, 12, 14) were allowed
to equilibrate with the appropriate reference compounds 1–
6 in THF. The relative stabilities derived from these experi-
ments are shown in Tables 1–3. Table 1 shows the results ob-
tained for a-oxy-alkyl organolithium compounds. Perusal of
these data allowed us to extract some interesting conclusions
on the substituents effects on organolithium stability.
The stability scale of organolithium compounds is defined in
terms of the Sn–Li exchange equilibrium reaction shown in
Equation (1). Measurement of the equilibrium constant of
this reaction provides a straightforward method for estab-
lishing the difference in thermodynamic stability (DGeq) be-
tween the involved organolithium compounds R1Li and
R2Li, where R2Li is used as a reference compound whose
stability has been previously established. A list of pK values
of aromatic and heteroaromatic carbanions which could be
used as reference compounds in THF is available from the
work of Fraser and co-workers, who measured the proton
transfer equilibrium constants of hydrocarbons 1c–6c with
bases of known pK to establish their basicity scale.[7] From
Fraserꢀs original pK data in tetrahydrofuran we calculated
the DGeq values[8] shown in Figure 1. The reference level of
Figure 1. Reference compounds used for tin–lithium exchange reactions.
DGeq values in kcalmolꢀ1, T=223 K.
0.0 kcalmolꢀ1 was assigned to 9-xanthenyllithium, the most
stable reference compound used in our previous study.[2] As
a first test of our method we chose to measure the relative
stabilities of the reference aromatic and heteroaromatic
compounds 1–6 in order to check if our measurements were
congruent with Fraserꢀs basicity scale. The Sn–Li exchange
equilibria were achieved by mixing equimolar amounts of
stannane (R1SnBu3 or R1SnMe3) and organolithium reagents
1b–6b at the appropriate temperature in THF. The concen-
trations of the relevant stannanes and organolithium species
at equilibrium were measured by NMR or GC after low-
temperature protonation with deoxygenated methanol (see
ref. [2] for details). The reverse reaction was performed in
every case to ensure that the equilibrium point had been
reached. The DGeq data are reported as a single number
when the same Keq was obtained from the forward and re-
verse reactions, and as an interval when proximate but non-
coincident values were obtained.
Effect of the O-substituent: The same degree of stabilization
to the a-carbanion was imparted by an alkyl or an alkox-
yalkyl group as the O-substituent (compare entries 1 and 2,
Table 1), thus the organolithium does not seem to experi-
ence an increased stabilization due to the formation of a
five-membered chelate with the Li cation through the addi-
tional oxygen over the one already present through the
three-membered ring chelation with the a-oxygen, thus cast-
ing some shadows on the generally accepted notion that a
five-membered ring Li–O chelate is present in these organo-
metallics.[5,11] For this particular study tributyltin derivatives
8a and 8b were used instead of the less hindered trimethyl-
tin analogues to avoid volatility problems due to their low
molecular weight.
R1SnR3 þ R2Li Ð R1Li þ R2SnR3
ð1Þ
As it had already been noticed in our previous study of
benzylic organometallics, an a-oxycarbanion is better stabi-
lized when a carbonyl derivative is used as the O-protecting
group than when alkyl or alkoxyalkyl groups are employed
(compare entries 1–5).[2] The extent of the additional stabili-
3
3
It has been established that the Sn–Li exchange reactions
proceed through the formation of pentasubstituted stannate
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Chem. Eur. J. 2007, 13, 2277 – 2289

Organolithium Compounds
FULL PAPER
Table 1. Relative stability data of a-oxy-alkyllithium compounds 7.
the presence of up to two alkyl groups at the b-position to
the carbon bearing the negative charge has a negligible
effect on carbanion stability, as the same DGeq was observed
with methyl-, ethyl-, butyl- or isopropyl-substituted organo-
lithiums 7g–j (compare entries 8–11). An exception to this
destabilizing effect of alkyl groups directly attached to the
carbanionic center seems to be displayed by the tert-butyl
group (compare entries 3,4 with 12,13), since the tert-butyl
substituted carbanion 7k is apparently as stable as the un-
substituted parent anion 7c and more stable that the other
alkyl substituted anions 7g–j. We attribute this behavior not
to an specific stabilizing effect of the tert-butyl group, but to
the release of steric strain, present in the starting stannane
due to the interaction between the large tert-butyl and
Me3Sn groups, upon Sn–Li exchange, which should shift the
equilibrium towards the anion 7k, thus making it apparently
more stable than the electron-donating properties of the
tert-butyl group would suggest.[13,14] The stability of a slightly
less sterically crowded neopentylic carbanion, such as the
cyclohexylmethyl substituted carbamate 7l (entry 14), is in
line (DDGeq =2.0 kcalmolꢀ1) with those of the methyl-,
ethyl- and isopropyl-substituted organolithium species,
which lends credit to the hypothesis that steric strain in the
organostannane lays at the origin of the anomalous behav-
ior of the tert-butyl substituted system.
Entry[a]
Anion
R1
R2
ArLi
DGeq
[b]
1
2
3
4
5
6
7
8
7a
7b
7c
7c
7d
7e
7 f
7g
7h
7i
H
H
H
H
CH3
1
1
2
3
2
5
2
1
1
1
1
3
4
7.9
7.9
5.5
5.4
6.0–5.9
4.7
1.6
7.5
7.5
7.5
7.5
5.4
5.5
MOM[b]
Cby
Cby
H
COR3[c]
ACHTER(UGN CH2)11CH3
CH2=
CH2=
CH3
CH3CH2
Cby
Cby
Cby
Cby
Cby
Cby
Cby
9
10
11
12
13
CH
(CH3)2CH
(CH3)3C
(CH3)3C
(CH2)3
7j
7k
7k
T
N
C
14
15
7l
Cby
1
7.5
7m
CH
(CH2)8
MOM[b]
PhLi
>11.5
Entry[a]
Anion
R1
R2
ArLi
DGeq
16
17
7g
7k
CH3
AHCTRE(UNG CH3)3C
Cby
Cby
1
1
7.5
7.8
To validate this explanation we decided to explore the
use of the equilibrium exchange reactions between lithium
and lead to establish the relative stabilities of organolithium
18
7l
Cby
1
7.5
[a] Reaction conditions: ꢀ508C/12 h for entries 1–2; ꢀ658C/16 h for en-
tries 3–4, 8–10 and 15; ꢀ508C/16 h for entries 5–6 and 14; ꢀ358C/24 h
for entries 11–13; ꢀ788C/6 h for entry 7; ꢀ258C/20 h and 24 h for entries
16 and 17. [b] The Bu3Sn derivative was used. [c] R3 = triisopropylphen-
yl.
compounds.[15] The longer carbon lead bond lengths should
ꢀ
result in diminished steric interactions in the starting orga-
nolead compounds, as compared to their tin counterparts,
so the measured carbanion stabilities should be less effected
by the steric compression of the starting materials. The Li–
Pb exchange reaction has been far less studied and utilized
than its Li–Sn counterpart, thus we decided to carry out a
preliminary study of its characteristics. Firstly, the prepara-
tion of the required a-oxy-organolead precursors 8g,l and
the reference compound 2-trimethyllead-anisole follows
closely that of their tin analogues.[16] The equilibrium ex-
change reactions between organolithiums 7g,l and 2-trime-
thyllead-anisole (and their reverse reactions) proceeded
under the same conditions, and provided the same relative
stability values, as the homologous Sn–Li exchanges (com-
pare entries 8 and 14 with 16 and 18). In this way we
showed that the lead–lithium exchange equilibrium reaction
is a valid alternative to the tin–lithium method of establish-
ing the relative stabilities of organolithium species. We then
determined the stability of the tert-butyl substituted carban-
ion 7k, using the lead–lithium exchange, and observed a de-
stabilization of about 2.4 kcalmolꢀ1 when compared with the
unsubstituted parent carbanion 7c (entry 17 versus entries 3,
4), in line with the effects of all the other alkyl substituents.
This result lends credence to our hypothesis of steric crowd-
ing in the tin precursor as the origin of the anomalous stabil-
ity measured for 7k using the Sn–Li method.
zation imparted by the carbonyl group depends on the
nature of the other substituent of the carbanionic center. A
difference in stability of approximately DDGeq =2–
2.5 kcalmolꢀ1 (a value close to that observed in the benzylic
series, 3 kcalmolꢀ1) is obtained when no further substitution
is present at the carbon bearing the negative charge.[12]
A
similar stabilization (DDGeq =3.1 kcalmolꢀ1) is observed for
the vinyl-lithiums 7e–f (compare entries 6 and 7). But when
the carbanionic center is further substituted by an alkyl
group (compare entries 9 and 15) a larger stability differ-
ence is observed (DDGeq >4 kcalmolꢀ1).
Effect of alkyl substituents attached to the carbon bearing
the negative charge in a-oxy-organolithium compounds:
When a carbamoyl (Cby) group is used as the O-substituent,
the incorporation of an alkyl residue attached to the carba-
nionic center is destabilizing by about 2 kcalmolꢀ1, probably
due to the electron-donating properties of the alkyl groups
(compare entries 3,4 with 8–11).[13,14] It is remarkable that
When a MOM group is used as the O-substituent, the in-
corporation of an alkyl residue attached to the a-carbanion-
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2279

F. J. Sardina et al.
ic center is far more destabilizing than when a carbamate
group is employed (>3.6 kcalmolꢀ1, compare entry 2 with
15), which indicates that the amount of destabilization im-
parted by alkyl groups depends on the type of organolithium
to which it is attached. We can only provide a lower range
estimation of this effect since the stability of MOMO-dec-
anyllithium 7m happened to be outside of the range that
could be measured using the reference compounds available
(up to about DGeq =9.7 kcalmolꢀ1 by using compound 1).
When we treated the stannylated acetal 8m with BuLi,
clean Sn–Li exchange was observed leading to anion 7m.
But when 7m was treated with Me3Sn-anisole (1a), we ob-
served the formation of small amounts of a new compound
to which structure 10 was tentatively assigned. This product
can be explained if 7m and MeLi have similar stabilities.[17]
Indeed, when the tributyltin analogue of 8m was treated
shown above it can be clearly deduced that the effects of
alkyl groups on the stability of organolithium compounds
are highly dependent on the structure of the involved carb-
anion, even for closely related systems. We propose that the
extent of the destabilization imparted by an alkyl group di-
rectly attached to a carbon bearing a negative charge is a
good measure of the negative charge stabilizing capabilities
of the rest of the substituents attached to that carbon (the
corollary is that the less stable a carbanion is, the more de-
stabilized it gets by alkyl substitution). Thus it appears that
an O-carbamoyl group withdraws more negative charge
from the carbon directly attached to it than an O-alkyl or an
O-alkoxyalkyl group.
Effect of remote substituents on alkyllithium stability: che-
lation: Once it had been established that the Sn–Li ex-
change equilibria could be used to study the effect of alkyl
groups directly attached to the anionic carbon on the stabili-
ty of organolithium compounds, we set out to apply this
method to determine the effects of remote substituents on
organolithium stability, particularly the effects of Li chela-
tion by heteroatoms.
Chelation effects have been implicated in a wide variety
of aspects of organolithium chemistry, from structure and
aggregation to reactivity and selectivity.[20a] Despite 40 years
of research into the origins and applications of these chela-
tion effects, there is still a lack of quantitative data on the
strength, or even the occurrence, of these types of interac-
tions in solution.[20b–f] Table 2 shows the stability data mea-
sured for a series of organolithium compounds bearing side
chains containing potential Li-chelating groups: N, O and S
atoms (cation-lone pair interaction). It can be readily seen
that the formation of four-membered (DDGeq =
1.7 kcalmolꢀ1 for N, compare entry 1 of Table 2 with en-
tries 8 or 9 of Table 1)[21] and five-membered (DDGeq =2.5–
with PhLi the [PhLi]/ACHTRE[UNG 7m] ratio at equilibrium was 87:13,
from which a DGeq =1.7 kcalmolꢀ1 relative to phenyllithium
was derived. The main problem with this measurement is
that the pK of benzene in THF has not been unambiguously
determined.[18] We established a minimum DGeq value for
PhLi from the fact that it completely undergoes Sn–Li ex-
change with Me3Sn-anisole (1a) (DGeq =7.7 kcalmolꢀ1, pK=
39.0), thus providing a DGeq >9.7 kcalmolꢀ1 (pK>41) for
PhLi, and DGeq >11.5 kcalmolꢀ1 for MOM-protected orga-
nolithium 7m.
In some selected instances we used two different refer-
ence compounds to measure the relative stability of the a-
oxycarbanion, and the same, or very close results, were ob-
tained (compare entries 3 and 4, or entries 12 and 13). These
duplicate determinations reinforce the reliability of the re-
sults and the validity of the method. We also measured se-
lected equilibrium constants (7h, 11b and 11d) at different
temperatures, ranging from ꢀ65 to ꢀ358C, and concentra-
tions (for 7c, 7h, 11b and 11d), ranging from 0.02 to 0.2m,
and found that the values for the observed Keq were temper-
ature and concentration independent. These facts point to
two important conclusions: 1) the a-oxy-organolithium spe-
cies and the reference organolithium compounds have defi-
nite structures (aggregation states) under the experimental
conditions used; 2) the measured stabilities of the organo-
lithium compounds are not dependent on the nature or the
aggregation state of the reference compound employed.
The interpretation of the observed substituent effects in
structural terms depends on the aggregation states of the or-
Table 2. Effect of chelation on a-oxy-organolithium stability.
Entry
Anion
R
ArSnMe3
T [8C]/t [h]
DGeq
1
2
3
4
5
6
7
8
11a
11b
11c
11d
11e
11 f
11g
11h
11i
Me2N
Me2NCH2
2
2
1
2
1
2
2
1
2
2
2
1
1
ꢀ50/24
ꢀ55/24
ꢀ50/24
ꢀ50/24
ꢀ65/24
ꢀ50/24
ꢀ50/24
ꢀ65/24
ꢀ50/24
ꢀ50/24
ꢀ50/16
ꢀ50/24
ꢀ50/24
5.8
5.0
8.0
5.4–5.5
7.5
5.7
6.1
7.1
6.1
Me2N
MeOCH2
MeO(CH2)2
(CH2)2
6
ganolithiums 7a–m. Boche et al. have provided Li,13C cou-
ACHTREUNG
pling data that strongly suggest that O-carbamoyl-alkyllithi-
um compounds are monomeric in THF at low tempera-
tures.[19] Our own measurements (see below) support this
assert. In view of this fact, the destabilizing effect of alkyl
groups on the stability of O-carbamoyl-organolithiums can
be attributed exclusively to electron donation to the carba-
nionic center by the substituent, since the size of the alkyl
group appears to have little or no influence. With regard to
the aggregation states of a-lithio-ethers and acetals the sit-
uation is far less clear, although they appear to be dimers in
THF at low temperatures.[19] In any case, from the data
MOMOCH2
TIPSOCH2
(CH3)3COCH2
MeSCH2OCH2
MeSCH2
–
–
–
9
10
11
12
13
11j
11k
11l
5.4–5.5
5.5
7.5
11m
7.1
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Chem. Eur. J. 2007, 13, 2277 – 2289

Organolithium Compounds
FULL PAPER
2.0 kcalmolꢀ1 for N and O, compare entries 2 and 4 of
Table 2 with entries 8 or 9 of Table 1) chelate rings leads to
stabilization of this kind of organolithium compounds. How-
ever, Li–O or Li–N chelation involving the formation of a
six-membered ring provides no extra stabilization, as com-
pared with a non-chelating alkyl side chain in this type of
systems (DDGeq =0 kcalmolꢀ1, compare entries 3 and 5 of
Table 2 with entries 8 or 9 of Table 1). Additionally, it ap-
pears that Li–N chelation affords a greater stabilization than
its Li–O counterpart (by about half a kcalmolꢀ1, compare
entry 2 with 4, Table 2) and this is similar to the stabilization
imparted by a sulphur atom (DDGeq =0 kcalmolꢀ1, compare
entry 4 with 10, Table 2), which does not bind to the Li
counterion, but exerts a large stabilizing effect due to its
high polarizability.[20c]
It may be argued that the heteroatom in the side chain of
organolithiums 11 could be involved in intramolecular as
well as intermolecular coordination, but this last possibility
can be disregarded on the account of the lack of influence
of the concentration on the stability of organolithiums
11b,d, as mentioned before, as well as our NMR studies de-
scribed below.
an a-hydrogen at the carbanionic center by a methyl group
has an important destabilizing effect in the aliphatic series
of organolithium compounds, and the same trend is ob-
served in the more stable benzylic carbanion 13e although
with a smaller DDGeq (1.2–1.4 kcalmolꢀ1) value, a testament
of the capability of both the O-carbamoyl and phenyl sub-
stituents to withdraw the extra negative charge from the
anionic center.
The presence of an electron-donating or electron-with-
drawing substituent at the aromatic ring should clearly influ-
ence the stability of the benzylic carbanion. To test if our
method could be applied to the assessment of aromatic ring
substituent effects on anion stability we investigated com-
pounds 13a–d. It is well known that a methyl group donates
electrons through a mild hyperconjugation effect, and that a
methoxy group can exert an electron-donating resonance
effect although, due to the difference in electronegativity
between oxygen and carbon, it also causes an electron-with-
drawing inductive effect. The combination of these two fac-
tors results in that a MeO group is electron withdrawing at
the meta position but in para the electron-donating reso-
nance effect is more important.[22] The stability data ob-
tained through Sn–Li exchange of benzyllithium compounds
13a–d are concordant with the expected theoretical order.
The presence of a methoxy group in meta is slightly stabiliz-
ing while both a meta-methyl and a para-methoxy substitu-
ents exert a destabilizing effect (compare entry 3 with 2 and
4 in Table 3).
Influence of O-protecting groups of the side chain: Once it
had been demonstrated that the formation of a five-mem-
bered ring chelate gives an important stabilization to this
type of a-O-carbamoyl organolithiums, we decided to study
the influence of the side chain O-protecting group on the
stability of the organolithium compounds, in order to derive
potentially useful information to be used in synthetic en-
deavors. For this study we chose methyl (11d), methoxy-
methyl (11 f), triisopropylsilyl (11g), tert-butyl (11h) and
methyl-thiomethyl (11i) ethers (Table 2) as representative
O-protecting groups. The highest stabilization (DDGeq ~
2.0 kcalmolꢀ1) is observed with the smallest group (Me,
compare entries 4, Table 2 with entry 9, Table 1), the
amount of stabilization decreases when using more sterically
demanding groups (DDGeq =1.4 and 0.4 kcalmolꢀ1 for TIPS
and tert-butyl ether respectively, compare entries 7 and 8,
Table 2 with entry 9 of Table 1). The negative influence of
the steric bulk around the side chain heteroatom on the for-
mation of a five-membered chelate and its effect on the sta-
bility of the organolithiums is also observed with the acetals
11k–m. In this case, the less hindered dioxolane (11k)
showed a high stabilization (DDGeq =2.0 kcalmolꢀ1, com-
pare entry 11, Table 2 with entry 9 of Table 1), while its di-
methyl counterpart 11l, or the similarly substituted dioxane
11m, do not impart additional stabilization, as its DGeq
value is similar to the one measured for a plain alkyl chain
substituted organolithium (DDGeq =0.0–0.4 kcalmolꢀ1, com-
pare entries 12 and 13 with entry 5, Table 2 or with entry 9,
Table 1).
Table 3. Relative stability data of benzylic compounds 13.[a]
Entry
Anion
R1
R2
R3
ArSnMe3
t [h]
DGeq
1
2
3
4
5
6
13a[b]
13b[b]
13c[b]
13d[b]
13e[c]
13e[c]
H
H
H
OMe
H
H
H
H
H
H
Me
Me
5
5
5
5
5
6
12
24
16
24
1
0.8–0.9
1.3–1.4
0.8
1.8
2.2
Me
OMe
H
H
H
H
2
2.1
[a] All reactions were performed at ꢀ788C. [b] PG = CON
ACHTRE(UGN iPr)2. [c] PG
= Cby.
NMR studies on the aggregation states of a-carbamoyloxy-
organolithiums: Although the Sn–Li or Pb–Li exchange re-
actions can provide a useful relative scale of thermodynamic
stabilities of secondary a-oxy-organolithiums, care must be
exercised when deriving structure–stability relationships
from these data, since the aggregation states of the involved
organolithium species must be known if sound conclusions
are to be drawn: all the compounds studied should have the
same aggregation state in solution and, preferably, they
should be monomers.
Since our first foray into the measurement of the relative
stabilities of organolithium compounds had been in the
realm of benzylic anions,[2] we decided to revisit these sys-
tems in order to determine how the stability of such delocal-
ized anions is affected by substitution. The replacement of
To shed some light on the aggregation states of our orga-
nolithium species in solution we set up different experi-
Chem. Eur. J. 2007, 13, 2277 – 2289
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2281

F. J. Sardina et al.
ments. As discussed above, when equilibria were run at dif-
ferent concentrations ranging from 0.02 to 0.2m (for 7c, 7h,
11b and 11d) there was no noticeable change in the values
of the relative stabilities of the organolithium species, which
suggests that they are monomeric in THF. We then proceed-
tronic and chelating effects of the proximal and distal sub-
stituents of the anionic carbon, and not to differences in
their aggregation states.
1
6
ed to obtain H, Li and 13C NMR spectra[23] of selected a-
Conclusions
carbamoyloxy-organolithium compounds (see Table 4) to
Sn–Li and Pb–Li exchange equilibria have been established
as useful tools for the study of stability-structure relation-
ships of highly functionalized organolithium reagents. This
methodology provides valuable quantitative information
about the influence of a number of structural factors (elec-
tron-donating and -withdrawing capabilities of substituents,
steric and chelation effects) on the behavior of these highly
synthetically useful compounds.[26]
Table 4. 13C NMR data of selected a-oxy-organolithium compounds in
[D8]THF.[a]
d [ppm]
Dd[b]
1J(13C,6Li) [Hz]
ACHTREUNG
7c: R = H
80
29
42
41
43
43
broad signal
7
7e: R = Me
7g: R = iPr
7h: R = tBu
102
112
117
107
broad signal with Li
11.8 (t)
13.1 (t), 13.3 (t)[c]
10.0 (t)
11e: R = MeOACHTREUNG(CH2)3
Experimental Section
[a] T = 163 K. [b] Dd refers to the downfield shift of the O-substituted
carbon upon lithiation. [c] Two rotamers.
General: All reactions were performed under an inert atmosphere of
Argon in glassware that had been oven- or flame-dried. Reaction temper-
atures are reported as the temperature of the bath surrounding the
vessel. Tetrahydrofuran (THF) and diethyl ether (Et2O) were distilled
from sodium/benzophenone immediately before use; methylene chloride
(CH2Cl2), pyridine, diisopropylamine, diisopropylethylamine and tetra-
methylethylenediamine (TMEDA) were distilled from CaH2 and metha-
determine the aggregation states[24] of these compounds in a
0.2m [D8]THF solution at 163 K. It is known that organo-
lithium compounds tend to be less aggregated in electron
donor solvents as THF, which is the solvent used in all of
our equilibrium studies, and thus [D8]THF was chosen for
(OMe)2. 2,2,4,4-Tetramethyl-1,3-oxazolidine,[27]
nol was distilled from MgACHTREUNG
2,2,4,4-tetramethyl-1,3-oxazolidine-3-carbonyl chloride,[27] 1a,[28] 3a,[29]
4a,[30] 5a,[2] 6a,[31] methyl 2,4,6-triisopropylbenzoate,[32] 8b,[33] 12b,[34] and
12l,[35] were prepared according to the literature.
6
the NMR experiments. Li NMR of all the compounds stud-
ied showed only one singlet which indicates the presence of
only one species in solution (d=4.04 ppm for 7j, and d=
4.56 ppm for 7k and 11e). In the 13C NMR spectra of 7c, 7j,
7k and 11e (obtained from Li–Sn exchange of the corre-
N,N-Dimethyl-N-(2-trimethylstannanyl-pyrrol-1-yl)-amine (2a):[36] BuLi
(2.10 mL, 7.08 mmol, 3.29m in hexane) was added to a solution of 1-(di-
methylamino)pyrrole (850 mL, 7.08 mmol) in THF (7.2 mL) at 08C. After
2 h, Me3SnCl (7.40 mL, 7.40 mmol, 1.0m in THF) was added, the mixture
was stirred for 45 min at 08C, then quenched by addition of pH 7.0 phos-
phate buffer and partitioned between CH2Cl2 (25 mL) and phosphate
buffer (20 mL). The aqueous phase was extracted with CH2Cl2 (20 mL)
and the combined organic phase was washed with satd aq NaHCO3
(10 mL) and brine (20 mL), dried with Na2SO4, filtered and concentrated.
The residue was purified by bulb-to-bulb distillation (408C at 0.5 mmHg)
6
sponding stannane and LiBu) the signals originated by the
lithiated carbons were split into a triplet (Table 4) which in-
dicates that the carbon is coupled to only one lithium atom,
and the magnitude of the 13C,6Li coupling constants lie
within the range typical of monomeric species. Additionally,
these compounds showed remarkable downfield 13C-chemi-
cal shifts of the lithiated carbon atoms which is consistent
with a carbenoid nature of a-lithiated carbamates.[19]
Additionally we carried out NMR diffusion experi-
ments[25] on compounds 7i (R=butyl, a non-functionalized
side chain unable to provide a coordination site for aggrega-
and 2a was obtained as
(300 MHz, CDCl3): d=7.10 (dd, J=1.4, 2.6 Hz, 1H), 6.27 (m, 1H), 6.05
(dd, J=1.4, 3.6 Hz, 1H), 2.79 (s, 6H), 0.27 ppm (s, J
117Sn,1H)=55.1,
a
pale yellow oil (1.8 g, 94%). 1H NMR
AHCTREUNG(
JACHTREUNG(
119Sn,1H)=57.4 Hz, 9H); 13C NMR (75 MHz, CDCl3): d=133.4, 114.9
(J(117,119Sn,13C)=18.9 Hz),
(J(117,119Sn,13C)=42.9 Hz),
112.6
48.2,
(J(117,119Sn,13C)=50.1 Hz),
108.6
ꢀ9.2 ppm
(J(117Sn,13C)=361.1,
J(119Sn,13C)=377.8 Hz); elemental analysis calcd (%) for C9H18N2Sn
(272.97): C 39.60, H 6.65, N 10.26; found: C 39.69, H 6.75, N 9.88.
tion), 11b [R=Me2NACHTREU(NG CH2)2] and 11d [R=MeOACHTRE(UGN CH2)2] to
(2-Methoxyphenyl)-trimethylplumbane (1a-Pb): Following the literature
procedure[28] but using Me3PbCl instead of Me3SnCl, 2-bromoanisole
(909 mg, 4.86 mmol) afforded 1a-Pb as a colorless oil (1.4 g, 80%).
1H NMR (250 MHz, CDCl3, rotamers): d=7.45 (dd, J=1.6, 6.9 Hz, 1H),
7.29 (m, 1H), 6.97 (q, J=7.0 Hz, 1H), 6.87 (m, 1H), 3.79 (s, 3H),
detect any form of aggregation mediated by the heteroatoms
in the side chains; this type of aggregation would not in-
volve Li–C complexation and, therefore, would be undetect-
able by 6Li,13C coupling analysis. All three compounds
showed very similar diffusion behaviors (diffusion constants
in 0.1m solutions in [D8]THF at ꢀ788C: 1.37, 1.34, and 1.38
eꢀ10 m2 sꢀ1 for 7i, 11b, and 11d, respectively), a result that
indicates they must have very similar sizes and shapes in
THF solution, thus ruling out the formation of dimers by in-
termolecular interaction between the Li cation and the side
chain heteroatoms when they are present. We thus conclude
that the observed differences in stability among the organo-
lithium compounds that we have studied are due to the elec-
0.92 ppm (s, JACHTREUNG(
207Pb,1H)=67.0 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, ro-
tamers): d=163.3 (J(207Pb,13C)=16.2 Hz), 137.0 (J(207Pb,13C)=300.2 Hz),
136.8 (J(207Pb,13C)=43.8 Hz), 129.2 (J(207Pb,13C)=11.7 Hz), 121.4
(J(207Pb,13C)=62.0 Hz), 109.3 (J(207Pb,13C)=28.2 Hz), 55.4, ꢀ1.80 ppm
(J(207Pb,13C)=295.0 Hz); elemental analysis calcd (%) for C10H16O3Pb
(391.44): C, 33.42, H 4.49; found: C 33.45, H 4.76.
General procedure for alkyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carbox-
ylates 9c, f–k: A suspension of Na2CO3 (1.18 g, 11.1 mmol) and 2,2,4,4-
tetramethyl-1,3-oxazolidine (955 mg, 7.40 mmol) in CH2Cl2 (16 mL) was
treated with the corresponding alkyl chloroformate (11.1 mmol). The re-
action mixture was stirred in a Morton flask at room temperature for 5 h,
2282
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Chem. Eur. J. 2007, 13, 2277 – 2289

Organolithium Compounds
FULL PAPER
quenched by addition of NaOH (0.1m, 1 mL) and after being stirred for
15 min, dried with Na2SO4, filtered over Celite and concentrated. The
residue was purified by column chromatography (silica gel, EtOAc/
hexane 1:3) to give 9c, f–k as colorless oils.
1700 cmꢀ1 (C=O); elemental analysis calcd (%) for C12H24N2O3 (244.34):
C 58.99, H 9.90, N 11.47; found: C 59.01, H 9.98, N 11.54.
4-(N,N-Dimethylamino)butyl
boxylate (11c-H): Following the same procedure as for 9l, 4-(dimethyla-
mino)butanol (520 mL, 4.1 mmol) afforded 11c-H as colorless oil
2,2,4,4-tetramethyl-1,3-oxazolidine-3-car-
Methyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (9c): 93%
yield; 1H NMR (300 MHz, CDCl3, rotamers): d=3.58 and 3.57 (2s, 2H),
3.53 (brs, 3H), 1.42 and 1.40, 1.36 and 1.35, 1.28 and 1.27, 1.21 and
1.20 ppm (8s, 12H); 13C NMR (75 MHz, CDCl3, rotamers): d=152.7/
152.0, 95.3/94.4, 76.0/75.7, 60.3/59.3, 51.2, 26.2, 25.1/25.0, 23.9 ppm; IR
(CsI): n˜ =1704 cmꢀ1 (C=O); elemental analysis calcd (%) for C9H17NO3
(187.24): C 57.73, H 9.15, N 7.48; found: C 57.71, H 9.08, N 7.38.
a
(1.03 g, 93%). 1H NMR (300 MHz, CDCl3, rotamers): d=4.10 (m, 2H),
3.72 (s, 2H), 2.31 (t, J=7.2 Hz, 2H), 2.22 (s, 6H), 1.69 (m, 2H), 1.55 (m,
8H), 1.42 and 1.37 ppm (2s, 6H); 13C NMR (75 MHz, CDCl3, rotamers):
d=152.1/151.4, 95.1/94.1, 75.7/75.5, 63.8, 60.0/59.1, 58.8, 44.9, 26.4, 26.1,
24.9, 23.9, 23.7 ppm; IR (CsI): n˜ =1699 cmꢀ1 (C=O); elemental analysis
calcd (%) for C14H28N2O3 (272.39): C 61.73, H 10.36, N 10.28; found: C
61.71, H 9.98, N 10.41.
Vinyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (9 f): 97% yield;
1H NMR (250 MHz, CDCl3, rotamers): d=7.22 (ddd, J=1.7, 6.3, 14.0 Hz,
1H), 4.75 (m, 1H), 4.42 (dt, J=1.7, 6.3, 1H), 3.74 (s, 2H), 1.55 and
1.41 ppm (2brs, 12H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=149.0/
148.2, 141.2/141.1, 95.4/94.6, 94.2/94.1, 75.7/75.4, 60.3/59.7, 26.2, 25.0, 24.5,
23.3 ppm; IR (CsI): n˜ =1691 cmꢀ1 (C=O); elemental analysis calcd (%)
for C10H17NO3 (199.25): C 60.28, H 8.60, N 7.03; found: C 60.30, H 8.67,
N 7.41.
3-Methoxypropyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (11d-
H): A suspension of NaH (60% in mineral oil, 123 mg, 3.09 mmol) in
THF (15 mL) was treated with (3-hydroxypropyl)-2,2,4,4-tetramethyl-1,3-
oxazolidine-3-carboxylate (714 mg, 3.09 mmol) and after stirring at RT
for 20 min, MeI (290 mL, 4.63 mmol) was added. The resulting mixture
was stirred at RT for 6 h, quenched by addition of pH 7.0 phosphate
buffer and then partitioned between CH2Cl2 (20 mL) and phosphate
buffer (20 mL). The aqueous phase was extracted with CH2Cl2 (20 mL)
and the combined organic phase was washed with brine (20 mL), dried
with Na2SO4, filtered and concentrated. The resulting residue was puri-
fied by column chromatography (silica gel, EtOAc/hexane 1:6) to give
11d-H as a colorless oil (667 mg, 88%). 1H NMR (250 MHz, CDCl3, ro-
tamers): d=4.17 (m, 2H), 3.73 (s, 2H), 3.47 (m, 2H), 3.34 (s, 3H), 1.93
(m, 2H), 1.55 and 1.52 (2s, 6H), 1.42 and 1.36 ppm (2s, 6H); 13C NMR
(62.9 MHz, CDCl3, rotamers): d=152.5/151.7, 95.5/94.5, 76.0/75.8, 69.2,
61.4, 60.3/59.4, 58.4, 29.0, 26.2, 25.0, 23.9 ppm; IR (CsI): n˜ =1699 cmꢀ1
(C=O); elemental analysis calcd (%) for C12H23NO4 (245.32): C 58.75, H
9.45, N 5.71; found: C 58.47, H 9.56, N 5.72.
Ethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (9g) see ref. [37],
84% yield.
Propyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (9h): 97% yield;
1H NMR (300 MHz, CDCl3, rotamers): d=3.97 (m, 2H), 3.65 (s, 2H),
1.61 (m, 2H), 1.48, 1.44, 1.34 and 1.29 (4s, 12H), 0.90 ppm (m, 3H);
13C NMR (75 MHz, CDCl3, rotamers): d=152.4/151.7, 95.4/94.4, 76.1/
75.8, 65.9, 60.3/59.4, 26.4, 25.2, 24.0, 22.2, 10.7 ppm; IR (CsI): n˜ =
1699 cmꢀ1 (C=O); elemental analysis calcd (%) for C11H21NO3 (215.29):
C 61.37, H 9.83, N 6.51; found: C 61.01, H 10.05, N 6.65.
Pentyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (9i): 96% yield;
1H NMR (250 MHz, CDCl3, rotamers): d=4.07 (m, 2H), 3.72 (s, 2H),
1.64 (m, 2H), 1.56 and 1.52 (2s, 6H), 1.37 (m, 10H), 0.91 ppm (t, J=
6.8 Hz, 3H); 13C NMR (75 MHz, CDCl3, rotamers): d=152.3/151.6, 95.2/
94.2, 75.8/75.6, 64.0, 60.0/59.0, 28.2/27.9, 26.0, 24.8, 23.6; 21.8, 13.5 ppm;
IR (CsI): n˜ =1701 cmꢀ1 (C=O); elemental analysis calcd (%) for
C13H25NO3 (243.34): C 64.16, H 10.36, N 5.76; found: C 64.06, H 10.33, N
5.78.
4-Methoxybutyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (11e-
H): Following the same procedure as for 11d-H, (4-hydroxybutyl)-2,2,4,4-
tetramethyl-1,3-oxazolidine-3-carboxylate (790 mg, 3.22 mmol) afforded
11e-H as a colorless oil (785 mg, 94%). 1H NMR (250 MHz, CDCl3, ro-
tamers): d=4.09 (m, 2H), 3.72 (s, 2H), 3.41 (t, J=5.8 Hz, 2H), 3.33 (s,
3H), 1.66 (m, 4H), 1.55 and 1.51 (2s, 6H), 1.41 and 1.36 ppm (2s, 6H);
13C NMR (62.9 MHz, CDCl3, rotamers): d=152.2/151.4, 95.1/94.1, 75.7/
75.4, 71.6/71.5, 64.1, 63.7, 57.9, 26.0, 25.9/25.7, 25.3/25.2, 24.7, 23.5 ppm;
IR (CsI): n˜ =1699 cmꢀ1 (C=O); elemental analysis calcd (%) for
C13H25NO4 (259.35): C 60.21, H 9.72, N 5.40; found: C 60.53, H 10.06, N
5.43.
2-Methylpropyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (9j):
see ref. [37], 97% yield.
2,2-Dimethylpropyl
2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate
(9k):[37] The reaction was carried out in a sealed tube at 908C for 18 h
(96% yield).
3-(Methoxymethoxy)propyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carbox-
ylate (11 f-H): Chloromethyl methyl ether was added at 08C dropwise to
a solution of (3-hydroxypropyl)-2,2,4,4-tetramethyl-1,3-oxazolidine-3-car-
boxylate (640 mg, 2.77 mmol), and diisopropylethylamine (1.7 mL,
9.68 mmol) in CH2Cl2 (5.5 mL). The resulting mixture was stirred at RT
for 1 h, quenched by addition of pH 7.0 phosphate buffer and then parti-
tioned between CH2Cl2 (15 mL) and phosphate buffer (15 mL). The
aqueous phase was extracted with CH2Cl2 (10 mL) and the combined or-
ganic phase was washed with brine (20 mL), dried with Na2SO4, filtered
and concentrated. The resulting residue was purified by column chroma-
tography (silica gel, EtOAc/hexane 1:3) to give 11 f-H as a colorless oil
(2.5 g, 94%). 1H NMR (250 MHz, CDCl3, rotamers): d=4.62, (s, 2H),
4.21 (m, 2H), 3.73 (s, 2H), 3.62 (m, 2H), 3.35 (s, 3H), 1.96 (m, 2H), 1.56
and 1.52 (2s, 6H), 1.42 and 1.36 ppm (2s, 6H); 13C NMR (62.9 MHz,
CDCl3, rotamers): d=151.9/151.2, 95.7, 95.1/94.0, 75.6/75.3, 63.5, 60.9,
59.9/58.9, 54.3, 28.8, 25.9, 24.6, 23.4 ppm; IR (CsI): n˜ =1699 cmꢀ1 (C=O);
elemental analysis calcd (%) for C13H25NO5 (275.35): C 56.71, H 9.15, N
5.09, found: C 56.52, H 9.35, N 4.98.
(1-Methylcyclohexyl)methyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carbox-
ylate (9l): A suspension of NaH (60% in mineral oil, 515 mg, 12.9 mmol)
in THF (9.0 mL) was treated with (1-methylcyclohexyl)methanol (1.1 g,
8.6 mmol), the mixture was stirred at RT for 30 min and 2,2,4,4-tetra-
methyl-1,3-oxazolidine-3-carbonyl chloride[27] (1.97 g, 10.3 mmol) in THF
(8 mL) was added. The mixture was stirred in a sealed tube at 708C over-
night, then quenched by addition of pH 7.0 phosphate buffer (5 mL) and
partitioned between CH2Cl2 (20 mL) and phosphate buffer (20 mL). The
aqueous phase was extracted with CH2Cl2 (20 mL) and the combined or-
ganic phase was washed with brine (20 mL), dried with Na2SO4, filtered
and concentrated. The resulting residue was purified by column chroma-
tography (silica gel, EtOAc/hexane 1:6) to give 9l as a white solid (2.0 g,
82%). M.p. 83–848C (hexane); 1H NMR (300 MHz, CDCl3, rotamers):
d=3.86 and 3.85 (2s, 2H), 3.73 (s, 2H), 1.56 and 1.54 (2s, 6H), 1.42 and
1.38 (2s, 6H), 1.39 (m, 10H), 0.98 and 0.96 ppm (2s, 3H); 13C NMR
(75 MHz, CDCl3, rotamers): d=152.9/152.2, 95.7/94.5, 76.2/76.0, 73.4,
60.5/59.4, 34.7, 33.8/33.7, 26.6, 26.2, 25.4/25.3, 24.1, 22.9, 21.6 ppm; IR
(CsI): n˜ =1681 cmꢀ1 (C=O); elemental analysis calcd (%) for C16H29NO3
(283.41): C 67.81, H 10.31, N 4.94; found: C 67.43, H 10.45, N 4.97.
3-(3-Triisopropylsilyloxy)propyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-car-
boxylate (11g-H): Triisopropylsilylchloride (690 mL, 3.26 mmol) was
added to a solution of (3-hydroxypropyl)-2,2,4,4-tetramethyl-1,3-oxazoli-
dine-3-carboxylate (629 mg, 2.72 mmol) and imidazole (463 mg,
6.80 mmol) in DMF (1.3 mL). The resulting mixture was stirred at RT for
16 h and then poured over 2n HCl solution (10 mL) and extracted with
EtOAc (3”10 mL), the combined organic phase was washed with satd aq
NaHCO3 (15 mL) and brine (15 mL), dried with Na2SO4, filtered and
concentrated. The resulting residue was purified by column chromatogra-
2-(N,N-Dimethylamino)ethyl
2,2,4,4-tetramethyl-1,3-oxazolidine-3-car-
boxylate (11a-H): Following the same procedure as for 9l, 2-(dimethyla-
mino)ethanol (950 mL) afforded 11a-H as a colorless oil (1.86 g, 80%).
1H NMR (250 MHz, CDCl3, rotamers): d=4.18 (m, 2H), 3.72 (s, 2H),
2.58 (m, 2H), 2.28 (s, 6H), 1.56 and 1.52 (2s, 6H), 1.42 and 1.36 ppm (2s,
6H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=152.4/151.7, 95.5/94.6,
76.1/75.8, 62.1, 60.3/59.5, 57.7, 45.5, 26.2, 25.0, 23.8 ppm; IR (CsI): n˜ =
Chem. Eur. J. 2007, 13, 2277 – 2289
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2283

F. J. Sardina et al.
phy (silica gel, EtOAc/hexane 1:10) to give 11g-H as a colorless oil
(957 mg, 91%). 1H NMR (250 MHz, CDCl3, rotamers): d=4.19 (t, J=
6.2 Hz, 2H), 3.78 (m, 2H), 3.70 (s, 2H), 1.87 (m, 2H), 1.53 and 1.49 (2s,
6H), 1.39 and 1.34 (2s, 6H), 1.04 (m, 3H), 1.03 and 1.02 ppm (2s, 18H);
13C NMR (62.9 MHz, CDCl3, rotamers): d=152.6/151.9, 95.6/94.6, 76.1/
75.9, 61.4, 60.3/59.4, 59.9, 32.2, 26.3, 25.1, 23.9, 17.8/17.6, 12.2/11.7 ppm;
IR (CsI): n˜ =1702 cmꢀ1 (C=O); elemental analysis calcd (%) for
C20H41NO4Si (387.64): C 61.97, H 10.66, N 3.61; found: C 62.10, H 10.65,
N 3.51.
as
a
white solid (425 mg, 79%). M.p. 58–598C (hexane); 1H NMR
(250 MHz, CDCl3, rotamers): d=4.15 (m, 2H), 3.94 (td, J=11.9, 2.8 Hz,
2H), 3.80 (ddd, J=1.4, 5.4, 11.8 Hz, 1H), 3.70 (s, 2H), 1.77 (m, 2H), 1.56
(m, 2H), 1.52 and 1.48 (2s, 6H), 1.40, 1.39, 1.34 and 1.33 ppm (4s, 12H);
13C NMR (62.9 MHz, CDCl3, rotamers): d=152.1/151.4, 97.6, 95.2/94.1,
75.7/75.4, 65.4, 60.2/59.2, 60.0/59.0, 35.4, 30.8, 29.4, 26.0, 24.8, 23.6,
18.6 ppm; IR (CsI): n˜ =1695 cmꢀ1 (C=O); elemental analysis calcd (%)
for C16H29NO5 (315.41): C 60.93, H 9.27, N 4.44; found: C 60.74, H 9.37,
N 4.48.
General procedure for the synthesis of organostannanes 8 and 12: sBuLi
(1.25 mL, 1.50 mmol, 1.2m in hexane) was added to a precooled solution
(ꢀ788C) of the corresponding carbamate or ester (1.00 mmol) and
TMEDA (230 mL, 1.50 mmol) in Et2O (3.0 mL). After stirring at ꢀ788C
for 5 h, Me3SnCl (1.5 mL, 1.5 mmol, 1.0m in THF) was added to the reac-
tion mixture. The resulting solution was stirred at the same temperature
for 1 h, quenched by addition of pH 7.0 phosphate buffer and then parti-
tioned between Et2O (10 mL) and phosphate buffer (10 mL). The aque-
ous phase was extracted with Et2O (10 mL) and the combined organic
phase was washed with brine (10 mL), dried with Na2SO4, filtered and
concentrated. The residue was purified by column chromatography
(grade III neutral Al2O3, hexane to EtOAc/hexane 1:50).
3-tert-Butoxypropyl
2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate
(11h-H): Following the same procedure as for 9l, 3-tert-butoxypropan-1-
ol (1.3 mL, 9.73 mmol) afforded 11h-H as a colorless oil (2.7 g, 97%).
1H NMR (250 MHz, CDCl3, rotamers): d=4.18 (t, J=6.1 Hz, 2H), 3.73
(s, 2H), 3.44 (m, 2H), 1.88 (m, 2H), 1.56 and 1.52 (2s, 6H), 1.42 and 1.36
(2s, 6H), 1.18 ppm (s, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=
152.3/151.6, 95.2/94.2, 75.8/75.6, 72.1, 61.5/61.4, 60.0/59.1, 57.7/57.6, 29.7,
27.1, 26.1, 24.8, 23.7 ppm; IR (CsI): n˜ =1700 cmꢀ1 (C=O); elemental anal-
ysis calcd (%) for C15H29NO4 (287.40): C 62.69, H 10.17, N 4.87; found: C
62.34, H 10.40, N 4.91.
3-[(Methylthio)methoxy]propyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-car-
boxylate (11i-H): (3-Hydroxypropyl)-2,2,4,4-tetramethyl-1,3-oxazolidine-
3-carboxylate (634 mg, 3.28 mmol) was added to a solution of acetic an-
hydride (5.2 mL) and acetic acid (1.6 mL) in DMSO (7.7 mL). The result-
ing mixture was stirred at RT for 48 h and then poured over satd aq
Na2CO3 and extracted with CH2Cl2 (3”15 mL), the combined organic
phase was washed with H2O (20 mL) and brine (20 mL), dried with
Na2SO4, filtered and concentrated. The resulting residue was purified by
column chromatography (silica gel, EtOAc/hexane 1:10) to give 11i-H as
(Methoxymethyl)tributylstannane (8a): Following the literature proce-
dure[39] but using chloromethyl methyl ether previously centrifuged with
triethylamine in THF, 8a was prepared in 98% yield.
Trimethylstannanylmethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxyl-
ate (8c): Following the general procedure, 9c (1.17 g, 6.24 mmol) afford-
ed 8c as a pale yellow oil (2.09 g, 96%). 1H NMR (300 MHz, CDCl3, ro-
tamers): d=4.07 (m, 2H), 3.71 (s, 2H), 1.54, 1.48, 1.40 and 1.32 (4s,
1
117Sn,1H)=53.0,
JACHTREUNG(
119Sn,1H)=54.9 Hz, 9H);
a colorless oil (790 mg, 99%). H NMR (250 MHz, CDCl3, rotamers): d=
12H), 0.13 ppm (s,
J
A
13C NMR (75 MHz, CDCl3, rotamers): d=153.2/152.6, 95.1/94.1, 75.8/
75.6, 59.9/58.9, 56.2 (J(117Sn,13C)=385.3, J(119Sn,13C)=404.6 Hz), 26.1,
24.9/24.8, 23.7, ꢀ9.4 ppm (J(117Sn,13C)=328.1, J(119Sn,13C)=345.5 Hz); IR
(CsI): n˜ =1684 cmꢀ1 (C=O); elemental analysis calcd (%) for
C12H25NO3Sn (350.05): C 41.18, H 7.20, N 4.00; found: C 41.33, H 7.29, N
4.06.
4.63 (s, 2H), 4.18 (m, 2H), 3.73 (s, 2H), 3.62 (m, 2H), 2.22 (s, 3H), 1.97
(m, 2H), 1.56 and 1.53 (2s, 6H), 1.42 and 1.37 ppm (2s, 6H); 13C NMR
(62.9 MHz, CDCl3, rotamers): d=152.1/151.4, 95.2/94.2, 75.7/75.5, 74.7,
64.0, 61.0, 60.0/59.1, 28.6, 26.0, 24.8, 23.6, 13.3 ppm; IR (CsI): n˜ =
1698 cmꢀ1 (C=O); elemental analysis calcd (%) for C13H25NO4S (291.41):
C 53.58, H 8.65, N 4.81, S 11.00; found: C 53.35, H 8.90, N 4.71, S 10.76.
3-(Methylthio)propyl
2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate
Trimethylstannanylmethyl 2,4,6-triisopropylbenzoate (8d): Following the
general procedure but using tBuLi instead of sBuLi, 9d (710 mg,
(11j-H): Following the same procedure as for 9l, 3-(methylthio)propan-
1-ol (640 mL, 6.22 mmol) gave 11j-H as a colorless oil (1.61 g, 99%).
1H NMR (250 MHz, CDCl3, rotamers): d=4.18 (t, J=6.1 Hz, 2H), 3.72
(s, 2H), 2.57 (m, 2H), 2.10 (s, 3H), 1.95 (m, 2H), 1.55 and 1.51 (2s, 6H),
1.41 and 1.35 ppm (2s, 6H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=
152.0/151.3, 95.2/94.1, 75.7/75.5, 62.5, 60.0/59.0, 30.3, 28.2, 26.0, 24.8/24.7,
23.5, 14.9 ppm; IR (CsI): n˜ =1698 cmꢀ1 (C=O); elemental analysis calcd
(%) for C12H23NO3S (261.38): C 55.14, H 8.87, N 5.36, S 12.27; found: C
54.83, H 9.03, N 5.23, S 11.99.
2.71 mmol) gave 8d as
(250 MHz, CDCl3): d=7.02 (s, 2H), 4.36 (s, J(117,119Sn,1H)=16.4 Hz, 2H),
2.85 (m, 3H), 1.26 (d, J=7.0 Hz, 18H), 0.24 ppm (s, J
117Sn,1H)=53.6,
119Sn,1H)=55.4 Hz, 9H); 13C NMR (62.9 MHz, CDCl3): d=171.9
a
colorless oil (530 mg, 46%). 1H NMR
AHCTREUNG(
JACHTREUNG(
(J(117,119Sn,13C)=17.6 Hz), 149.9, 144.8, 130.7, 120.7 (J(117,119Sn,13C)=
58.7 Hz), 56.5 (J(117Sn,13C)=355.5, J(119Sn,13C)=371.8 Hz), 34.4, 31.5,
24.2, 23.9, ꢀ9.5 ppm (J(117Sn,13C)=330.0, J(119Sn,13C)=345.3 Hz); IR
(CsI): n˜ =1712 cmꢀ1 (C=O); elemental analysis calcd (%) for C20H34O2Sn
(425.20): C 56.50, H 8.06; found: C 56.73, H 8.29.
2-(1,3-Dioxolan-4-yl)ethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxyl-
ate (11k-H):
A suspension of NaH (60% in mineral oil, 810 mg,
(1-(Dodecyloxy)vinyl)trimethylstannane (8e): Following the general pro-
cedure but using tBuLi during 3 h from ꢀ78 to 08C instead of sBuLi, 1-
(vinyloxy)dodecane (541 mg, 2.55 mmol) afforded 8e (902 mg, 94%) as a
colorless oil. 1H NMR (250 MHz, CDCl3): d=4.66 (d, J=1.7,
J(117,119Sn,1H)=110.2 Hz, 1H), 4.08 (d, J=1.7, J(117,119Sn,1H)=35.7 Hz,
1H), 3.64 (t, J=6.5 Hz, 2H), 1.64 (m, 2H), 1.26 (m, 18H), 0.88 (m, 3H),
0.18 ppm (s, J(117,119Sn,1H)=55.1 Hz, 9H); 13C NMR (62.9 MHz, CDCl3):
20.2 mmol) in DMF (6.5 mL) was treated with 3,4-dihydroxybutyl 2,2,4,4-
tetramethyl-1,3-oxazolidine-3-carboxylate (662 mg, 2.53 mmol), the mix-
ture was stirred at RT for 45 min and dibromomethane (355 mL,
5.1 mmol) was added. The resulting mixture was stirred overnight at RT,
then poured over pH 7.0 phosphate buffer and partitioned between
CH2Cl2 (10 mL) and phosphate buffer (10 mL). The aqueous phase was
extracted with CH2Cl2 (3”5 mL) and the combined organic phase was
washed with brine (10 mL), dried with Na2SO4, filtered and concentrated.
The resulting residue was purified by column chromatography (silica gel,
EtOAc/hexane 1:6) to give 11k-H as a colorless oil (508 mg, 73%).
1H NMR (250 MHz, CDCl3, rotamers): d=5.03 (s, 1H), 4.88 (s, 1H), 4.23
(brt, J=6.6 Hz, 2H), 4.12 (m, 1H), 4.02 (t, J=7.0 Hz, 1H), 3.73 (s, 2H),
3.51 (m, 1H), 1.94 (m, 2H), 1.56 and 1.52 (2s, 6H), 1.42 and 1.36 ppm
(2s, 6H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=151.4/150.7, 94.7/
93.7, 93.8, 75.2/74.9, 72.2, 68.5, 60.4, 59.6/58.6, 31.9, 25.6, 24.3, 23.1 ppm;
IR (CsI): n˜ =1698 cmꢀ1 (C=O); elemental analysis calcd (%) for
C13H23NO5 (273.33): C 57.13, H 8.48, N 5.12; found: C 57.11, H 8.72, N
5.04.
d=172.7
(J(117Sn,13C)=544.5,
J(119Sn,13C)=569.8 Hz),
94.9
(J(117,119Sn,13C)=82.6 Hz), 66.8 (J(117,119Sn,13C)=27.9 Hz), 32.0, 29.7, 29.6,
29.5, 29.4, 29.0, 26.3, 22.7, 14.1, ꢀ9.6 ppm (J(117Sn,13C)=339.0,
J(119Sn,13C)=354.8 Hz); elemental analysis calcd (%) for C17H36OSn
(375.18): C 54.42, H 9.67; found: C 54.35, H 10.03.
1-(Trimethylstannyl)vinyl
2,2,4,4-tetramethyloxazolidine-3-carboxylate
(8 f): Following the general procedure, 9 f (418 mg, 2.10 mmol) afforded
8 f as a colorless oil (592 mg, 78%). 1H NMR (250 MHz, CDCl3, rotam-
ers): d=5.37 and 5.33 (2s, JACHRTEUN(G ACHTREUGN(
117Sn,1H)=91.1, J 119Sn,1H)=94.7 Hz, 1H),
4.62 and 4.61 (2s, J(117,119Sn,1H)=29.4 Hz, 1H), 3.74 (s, 2H), 1.56 and
1.54 (2s, 6H), 1.41 and 1.40 (2s, 6H), 0.17 ppm (s, J(117,119Sn,1H)=
55.7 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=163.8/163.6,
151.8/151.1, 107.8/107.7 (J(117,119Sn,13C)=70.9 Hz), 95.8/95.2, 76.3/76.1,
60.6/60.1, 26.7, 25.5, 25.0, 23.9, ꢀ6.5 ppm (J(117Sn,13C)=368.3,
J(119Sn,13C)=385.4 Hz); IR (CsI): n˜ =1691 cmꢀ1 (C=O); elemental analy-
2-(2,2-Dimethyl-1,3-dioxan-4-yl)ethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-
3-carboxylate (11m-H): Following the same procedure as for 9l, 2-(2,2-
dimethyl-1,3-dioxan-4-yl)ethanol[38] (272 mg, 1.70 mmol) afforded 11m-H
2284
www.chemeurj.org
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2277 – 2289

Organolithium Compounds
FULL PAPER
sis calcd (%) for C13H25NO3Sn (362.06): C 43.13, H 6.96, N 3.87; found:
C 43.41, H 7.17, N 4.00.
50.5, J
(
119Sn,1H)=52.5 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers):
d=153.0/152.2, 95.7/94.3, 82.8 (J(117Sn,13C)=439.4, J(119Sn,13C)=
457.1 Hz), 76.2/75.9, 60.5/59.2, 38.2, 35.7/35.6, 26.7/26.6, 26.1, 25.6/25.4,
25.3/24.9, 24.1/23.9, 22.8/22.7, 21.8, ꢀ7.3 ppm (J(117Sn,13C)=306.7,
J(119Sn,13C)=320.8 Hz); IR (CsI): n˜ =1673 cmꢀ1 (C=O); elemental analy-
sis calcd (%) for C19H37NO3Sn (446.22): C 51.14, H 8.36, N 3.14; found:
C 51.39, H 8.48, N 3.22.
1-(Trimethylstannanyl)ethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carbox-
ylate (8g): Compound 9g (342 mg, 1.70 mmol) gave 8g as a pale yellow
oil (537 mg, 87%). 1H NMR (300 MHz, CDCl3, rotamers): d=4.52 (q,
J=7.4 Hz, 1H), 3.67 (s, 2H), 1.50 (m, 9H), 1.37 and 1.33 (2s, 6H),
0.06 ppm (s,
JACHTREUNG( JACHTREUNG(
117Sn,1H)=51.2, 119Sn,1H)=53.6 Hz, 9H); 13C NMR
(75 MHz, CDCl3, rotamers): d=152.9/152.3, 95.5/94.5, 76.2/76.0, 66.7
(J(117Sn,13C)=431.7, J(119Sn,13C)=451.3 Hz), 60.3/59.5, 26.5/26.4, 25.4,
25.3/25.2, 24.3/24.1, 19.3, ꢀ9.6 ppm (J(117Sn,13C)=317.1, J(119Sn,13C)=
330.8 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=O); elemental analysis calcd (%)
for C13H27NO3Sn (364.07): C 42.89, H 7.47, N 3.85; found: C 43.09, H
7.61, N 3.79.
Tributyl-(1-methoxymethoxy-decyl)stannane (8m): A solution of diiso-
propylamine (440 mL, 3.17 mmol) in THF (10 mL) cooled to 08C was
treated with BuLi (1.8 mL, 2.77 mmol, 1.51m in hexane) and stirred for
15 min. Bu3SnH (700 mL, 2.64 mmol) was added, stirred at 08C for
15 min and then cooled to ꢀ788C. Decanal (400 mL, 2.10 mmol) was
added and the resulting mixture was stirred at ꢀ788C for 3.5 h. The reac-
tion was quenched by addition of satd aq NH4Cl solution (15 mL) and
partitioned between EtOAc (20 mL) and H2O (20 mL). The organic
layer was washed with H2O (20 mL) and brine (20 mL), dried with
Na2SO4, filtered and evaporated to give a residue which was immediately
treated with diisopropylethylamine (1.3 mL, 7.39 mmol) in CH2Cl2
(3.2 mL) and chloromethyl methyl ether (500 mL, 6.60 mmol), which had
been previously centrifuged with triethylamine (100 mL) in THF
(500 mL). After 12 h stirring at RT, the reaction mixture was partitioned
between CH2Cl2 (15 mL) and pH 7.0 buffer solution (15 mL). The organ-
ic layer was washed with brine (15 mL), dried with Na2SO4, filtered and
evaporated. The residue was purified by chromatography through a short
column of silica gel (EtOAc/hexane 1:100) to give 8m (511 mg, 49%) as
a colorless oil. 1H NMR (250 MHz, CDCl3): d=4.60 (d, J=6.6 Hz, 1H),
4.54 (d, J=6.6 Hz, 1H), 4.05 (t, J=6.6 Hz, 1H), 3.34 (s, 3H), 1.79 (m,
2H), 1.48 (m, 5H), 1.31 (m, 20H), 0.89 ppm (m, 19H); 13C NMR
1-(Trimethylstannanyl)propyl
2,2,4,4-tetramethyl-1,3-oxazolidine-3-car-
boxylate (8h): Compound 9h (1.05 g, 4.86 mmol) yielded 8h (1.72 g,
94%) as a colorless oil. 1H NMR (300 MHz, CDCl3, rotamers): d=4.48
(td, J=6.9, 2.5 Hz, 1H), 3.72 (s, 2H), 1.90 (m, 2H), 1.54 (brs, 6H), 1.40
and 1.37 (2s, 6H), 0.99 (td, J=7.3 Hz, 3.1, 3H), 0.10 ppm (s, J
51.2, J
119Sn,1H)=53.5 Hz, 9H); 13C NMR (75 MHz, CDCl3, rotamers):
d=153.0/152.3, 95.4/94.4, 76.1/75.9, 73.5
(J(117Sn,13C)=430.4,
ACHTREUNG(
117Sn,1H)=
ACHTREUNG(
J(119Sn,13C)=451.8 Hz), 60.3/59.3, 26.8, 26.5/26.4, 25.3, 24.2/24.1, 12.5
(J(117,119Sn,13C)=35.0 Hz), ꢀ9.1 ppm (J(117Sn,13C)=315.4, J(119Sn,13C)=
330.0 Hz); IR (CsI): n˜ =1678 cmꢀ1 (C=O); elemental analysis calcd (%)
for C14H29NO3Sn (378.10): C 44.47, H 7.73, N 3.70; found: C 44.86, H
7.99, N 3.76.
1-(Trimethylstannanyl)pentyl
2,2,4,4-tetramethyl-1,3-oxazolidine-3-car-
boxylate (8i): Compound 9i (800 mg, 3.29 mmol) yielded 8i (1.10 g,
82%) as a colorless oil. 1H NMR (250 MHz, CDCl3, rotamers): d=4.53
(m, 1H), 3.72 (s, 2H), 1.84 (m, 2H), 1.53 (m, 6H), 1.35 (m, 10H), 0.91 (t,
(62.9 MHz,
CDCl3):
d=96.3
(J(117,119Sn,13C)=18.8 Hz),
74.0
(J(117Sn,13C)=385.7, J(119Sn,13C)=403.7 Hz), 55.4, 35.1, 31.9, 29.6, 29.5,
29.3, 29.2 (J(117,119Sn,13C)=19.9 Hz), 27.9 (J(117,119Sn,13C)=29.5 Hz), 27.5
(J(117Sn,13C)=53.3, J(119Sn,13C)=55.4 Hz), 22.7, 14.1, 13.7, 9.2 ppm
(J(117Sn,13C)=290.0, J(119Sn,13C)=303.4 Hz); elemental analysis calcd
(%) for C24H52O2Sn (491.39): C 58.66, H 10.67; found: C 58.55, H 10.69.
J=6.7 Hz, 3H), 0.09 ppm (s,
JAHCTREUN(G JACHTREUGN(
117Sn,1H)=51.3, 119Sn,1H)=53.3 Hz,
9H); 13C NMR (75 MHz, CDCl3, rotamers): d=153.1/152.5, 95.4/94.4,
76.1/75.9, 71.7 (J(117Sn,13C)=434.1, J(119Sn,13C)=453.9 Hz), 60.2/59.2,
33.2, 29.8 (J(117,119Sn,13C)=33.5 Hz), 26.3, 25.1, 24.0/23.9, 22.2, 13.8,
ꢀ9.3 ppm (J(117Sn,13C)=316.4, J(119Sn,13C)=331.1 Hz); IR (CsI): n˜ =
1678 cmꢀ1 (C=O); elemental analysis calcd (%) for C16H33NO3Sn
(406.15): C 47.32, H 8.19, N 3.45; found: C 47.53, H 8.52, N 3.14.
1-(Trimethylplumbyl)ethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxyl-
ate (8g-Pb): Following the general procedure for the synthesis of organo-
stannanes but using Me3PbBr instead of Me3SnCl, 9g (303 mg,
2-Methyl-1-(trimethylstannanyl)propyl
2,2,4,4-tetramethyl-1,3-oxazoli-
1.56 mmol) gave 8g-Pb (680 mg, 96%) as
(300 MHz, CDCl3, rotamers): d=5.20 (q, J=7.2, J
1H), 3.72 (s, 2H), 1.98 and 1.75 (2 d, J=3.6, J
207Pb,1H)=113.8 Hz, 3H),
1.54 and 1.52 (2s, 6H), 1.41, 1.40, 1.37 and 1.36 (4s, 6H), 0.7 ppm (s,
207Pb,1H)=57.2 Hz, 9H); 13C NMR (75 MHz, CDCl3, rotamers):
a
colorless oil. 1H NMR
207Pb,1H)=55.0 Hz,
dine-3-carboxylate (8j): Compound 9j (991 mg, 4.32 mmol) gave 8j
1
AHCTREUNG(
(1.57 g, 93%) as a pale yellow oil. H NMR (300 MHz, CDCl3, rotamers):
AHCTREUNG(
d=4.41 and 4.40 (2 d, J=6.5 Hz, 1H), 3.72 (s, 2H), 2.21 and 2.20 (2 sept,
J=6.7 Hz, 1H), 1.54 (s, 6H), 1.40 and 1.38 (2s, 6H), 0.99 and 0.98 (2 d,
JAHCTREUN(G JACHTREUGN(
117Sn,1H)=50.9, 119Sn,1H)=53.1 Hz,
JACHTREUNG(
J=6.7 Hz, 6H), 0.11 ppm (s,
d=152.4/151.8, 95.5/94.6, 76.2/76.0, 72.0 (J(207Pb,13C)=428.7 Hz), 60.2/
59.4, 26.4/26.3, 25.2/25.1, 24.1/23.9, 21.2 (J(207Pb,13C)=13.1 Hz), ꢀ2.2 ppm
(J(207Pb,13C)=197.4 Hz); IR (CsI): n˜ =1688 cmꢀ1 (C=O); elemental anal-
ysis calcd (%) for C13H27NO3Pb (452.56): C 34.50, H 6.01, N 3.10; found:
C 34.28, H 6.36, N 3.16.
9H); 13C NMR (75 MHz, CDCl3, rotamers): d=153.3/152.6, 95.8/94.6,
79.2, 76.3/76.1, 60.5/59.5, 32.0, 26.6/26.5, 25.3, 24.2/24.1, 21.0
(J(117,119Sn,13C)=27.6 Hz), 20.3/20.2, ꢀ8.4 ppm (J(117Sn,13C)=314.4,
J(119Sn,13C)=328.7 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=O); elemental analy-
sis calcd (%) for C15H31NO3Sn (392.13): C 45.95, H 7.97, N 3.57; found:
C 46.23, H 8.09, N 3.42.
2,2-Dimethyl-1-(trimethylplumbyl)propyl 2,2,4,4-tetramethyl-1,3-oxazoli-
dine-3-carboxylate (8k-Pb): Following the general procedure for the syn-
thesis of organostannanes but at ꢀ308C and using Me3PbBr instead of
Me3SnCl, 9k (640 mg, 2.63 mmol) gave 8k-Pb (915 mg, 70%) as a color-
less oil. 1H NMR (250 MHz, CDCl3, rotamers): d=5.20 and 5.19 (2s,
2,2-Dimethyl-1-(trimethylstannanyl)propyl
2,2,4,4-tetramethyl-oxazoli-
dine-3-carboxylate (8k): Following the general procedure with a reaction
temperature of ꢀ308C, 9k (400 mg, 1.64 mmol) gave 8k (502 mg, 75%)
as a colorless oil. 1H NMR (250 MHz, CDCl3, rotamers): d=4.67 and
4.66 (2s, J(117,119Sn,1H)=14.3 Hz, 1H), 3.73 (s, 2H), 1.56 and 1.55 (2s,
6H), 1.42 and 1.40 (2s, 6H), 1.02 and 1.01 (2s, 9H), 0.14 ppm (s,
J
A
207Pb,1H)=40.0 Hz, 1H), 3.74 (s, 2H), 1.57, 1.56 and 1.55 (3s, 6H), 1.42,
1.41 and 1.40 (3s, 6H), 1.04 and 1.03 (2 s, 9H), 0.76 ppm (s, J
207Pb,1H)=
AHCTREUNG(
54.8 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=152.2/151.4,
95.7/94.2, 90.3 (J(207Pb,13C)=446.0 Hz), 76.1/75.9, 60.4/59.2, 36.8, 28.1
(J(207Pb,13C)=38.5 Hz), 26.7/26.6, 25.6/25.4, 25.2/24.7, 24.1/23.8,
ꢀ0.12 ppm (J(207Pb,13C)=180.9 Hz); IR (CsI): n˜ =1689 cmꢀ1 (C=O); ele-
mental analysis calcd (%) for C16H33NO3Pb (494.65): C 38.85, H 6.72, N
2.83; found: C 38.99, H 7.08, N 2.93.
J
A
117Sn,1H)=50.6,
JACHTREUNG(
119Sn,1H)=52.8 Hz, 9H); 13C NMR (62.9 MHz,
CDCl3, rotamers): d=152.8/152.1, 95.6/94.1, 82.9 (J(117Sn,13C)=438.4,
J(119Sn,13C)=458.5 Hz), 76.1/75.8, 60.3, 59.0, 35.8, 27.9, 26.5, 25.4/25.3,
25.1/24.8, 24.0/23.8, ꢀ7.4 ppm (J(117Sn,13C)=309.9, J(119Sn,13C)=
324.2 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=O); elemental analysis calcd (%)
for C16H33NO3Sn (406.16): C 47.32, H 8.19, N 3.45; found: C 47.66, H
8.57, N 3.30.
(1-Methylcyclohexyl)(trimethylplumbyl)methyl
2,2,4,4-tetramethyl-1,3-
oxazolidine-3-carboxylate (8l-Pb): Following the general procedure for
the synthesis of organostannanes but at ꢀ308C and using Me3PbBr in-
stead of Me3SnCl, 9l (635 mg, 2.24 mmol) gave 8l-Pb (610 mg, 51%) as a
white solid. M.p. 83–848C (hexane); 1H NMR (250 MHz, CDCl3, rotam-
(1-Methylcyclohexyl)-1-(trimethylstannanyl)methyl 2,2,4,4-tetramethyl-
1,3-oxazolidine-3-carboxylate (8l): Following the general procedure with
a
reaction temperature of ꢀ308C, 9l (705 mg, 2.49 mmol) gave 8l
(610 mg, 75%) as
a
white solid. M.p. 64–658C (hexane); 1H NMR
ers): d=5.41 and 5.40 (2s, J
and 1.55 (2s, 6H), 1.41 and 1.39 (2s, 6H), 1.38 (m, 10H), 1.03 and 1.01
(2s, 3H), 0.76 ppm (s, J
207Pb,1H)=54.2 Hz, 9H); 13C NMR (62.9 MHz,
ACHTREUNG(
207Pb,1H)=37.1 Hz, 1H), 3.73 (s, 2H), 1.57
(250 MHz, CDCl3, rotamers): d=4.89 and 4.87 (2s, J(117,119Sn,13C)=
15.6 Hz, 1H), 3.73 (s, 2H), 1.57 and 1.55 (2s, 6H), 1.54–1.28 (m, 10H),
1.41 and 1.39 (2s, 6H), 1.00 (d, J=4.3 Hz, 3H), 0.14 ppm (s, J
A
117Sn,1H)=
ACHTREUNG(
Chem. Eur. J. 2007, 13, 2277 – 2289
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2285

F. J. Sardina et al.
CDCl3, rotamers): d=152.5/151.7, 95.9/94.5, 90.4 (J(207Pb,13C)=451.9 Hz),
76.3/76.0, 60.6/59.4, 39.2, 36.1 (J(207Pb,13C)=33.2 Hz) and 35.9
(J(207Pb,13C)=50.8 Hz), 26.9/26.7, 26.2, 25.8/25.6, 25.3/24.8, 24.3/23.9, 23.2/
23.1 (J(207Pb,13C)=34.7 Hz), 22.0, 0.03 ppm (J(207Pb,13C)=175.7 Hz); IR
(CsI): n˜ =1675 cmꢀ1 (C=O); elemental analysis calcd (%) for
C19H37NO3Pb (534.71): C 42.68, H 6.97, N 2.62; found: C 43.00, H 7.29, N
2.69.
for C16H33NO5Sn (438.15): C 43.86, H 7.59, N 3.20; found: C 44.24, H
7.68, N 3.37.
3-(Triisopropylsilyloxy)-1-(trimethylstannanyl)-propyl 2,2,4,4-tetramethyl-
1,3-oxazolidine-3-carboxylate (12g): Compound 11g-H (437 mg,
1.13 mmol) afforded 12g (547 mg, 88%) as a colorless oil. 1H NMR
(250 MHz, CDCl3, rotamers): d=4.58 (m, 1H), 3.74 (m, 2H), 3.68 (s,
2H), 2.10 (m, 2H), 1.50 and 1.48 (2s, 6H), 1.36 and 1.32 (2s, 6H), 1.03
and 1.01 (2s, 21H), 0.07 ppm (s, J(117,119Sn,1H)=52.5 Hz, 9H); 13C NMR
(62.9 MHz, CDCl3, rotamers): d=153.2/152.5, 95.7/94.5, 76.2/76.0, 68.0
(J(117Sn,13C)=425.9, J(119Sn,13C)=445.7 Hz), 61.6 (J(117,119Sn,13C)=
51.2 Hz), 60.4/59.4, 37.0, 26.4, 25.3/25.2, 24.1/24.0, 17.9, 11.9
(J(117Sn,13C)=59.1 Hz), ꢀ9.3 ppm (J(117Sn,13C)=319.2, J(119Sn,13C)=
333.7 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=O); elemental analysis calcd (%)
for C23H49NO4SiSn (550.45): C 50.19, H 8.97, N 2.54; found: C 50.35, H
9.18, N 2.63.
2-(N,N-Dimethylamino)-1-(trimethylstannanyl)ethyl 2,2,4,4-tetramethyl-
1,3-oxazolidine-3-carboxylate (12a): Compound 11a-H (715 mg,
2.90 mmol) afforded 13a (814 mg, 69%) as a colorless oil. 1H NMR
(250 MHz, CDCl3, rotamers): d=4.71 (m, 1H), 3.60 (s, 2H), 2.57 (m,
2H), 2.10 (s, 6H), 1.42 (s, 6H), 1.29 and 1.24 (2s, 6H), ꢀ0.01 ppm (s,
J(117,119Sn-1H)=52.9 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers):
d=152.9/152.2,
95.5/94.5,
76.1/75.9,
70.3
(J(117Sn,13C)=433.0,
J(119Sn,13C)=452.7 Hz), 70.2 (J(117Sn,13C)=433.0, J(119Sn,13C)=447.8 Hz),
61.4, 60.2/59.3, 45.8, 26.3/26.2, 25.1, 24.0/23.9, ꢀ9.2 ppm (J(117Sn,13C)=
322.2, J(119Sn,13C)=337.2 Hz); IR (CsI): n˜ =1683 cmꢀ1 (C=O); elemental
analysis calcd (%) for C15H32N2O3Sn (407.14): C 44.25, H 7.92, N 6.88;
found: C 44.22, H 8.07, N 6.77.
3-tert-Butoxy-1-(trimethylstannanyl)propyl 2,2,4,4-tetramethyl-1,3-oxazo-
lidine-3-carboxylate (12h): Compound 11h-H (1.35 g, 4.70 mmol) afford-
ed 12h (1.95 g, 92%) as a colorless oil. 1H NMR (250 MHz, CDCl3, ro-
tamers): d=4.64 (m, 1H), 3.72 (s, 2H), 3.44 (m, 2H), 2.07 (m, 2H), 1.54
and 1.52 (2s, 6H), 1.40 and 1.36 (2s, 6H), 1.18 (s, 9H), 0.10 ppm (s,
4-(N,N-Dimethylamino)-1-(trimethylstannanyl)butyl 2,2,4,4-tetramethyl-
1,3-oxazolidine-3-carboxylate (12c): Compound 11c-H (687 mg,
2.52 mmol) afforded 12c (852 mg, 78%) as a colorless oil. 1H NMR
(250 MHz, CDCl3, rotamers): d=4.53 (m, 1H), 3.71 (s, 2H), 2.30 (t, J=
7.5 Hz, 2H), 2.22 (s, 6H), 1.85 (m, 2H), 1.58 (m, 2H), 1.53 and 1.51 (2s,
J
A
117Sn,1H)=51.9,
JACHTREUNG(
119Sn,1H)=53.5 Hz, 9H); 13C NMR (62.9 MHz,
CDCl3, rotamers): d=153.0/152.4, 95.5/94.4, 76.1/75.9, 72.5, 68.5
(J(117Sn,13C)=429.1, J(119Sn,13C)=450.5 Hz), 60.3/59.8, 59.5, 59.3, 34.6,
27.3, 26.4/26.3, 25.2/25.1, 24.0/23.9, ꢀ9.2 ppm (J(117Sn,13C)=319.0,
J(119Sn,13C)=333.8 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=O); elemental analy-
sis calcd (%) for C18H37NO4Sn (450.21): C 48.02, H 8.28, N 3.11; found:
C 47.65, H 8.54, N 2.84.
6H), 1.40 and 1.36 (2s, 6H), 0.10 ppm (s, JACHRTENUG( ACHTREUNG(
117Sn,1H)=51.3, J 119Sn,1H)=
53.4 Hz, 9H); 13C NMR (75 MHz, CDCl3, rotamers): d=152.8/152.2,
95.3/94.3, 76.0/75.8, 71.5 (J(117Sn,13C)=427.8, J(119Sn,13C)=447.2 Hz),
60.1/59.2, 59.4, 45.2, 31.4, 26.4/26.3, 25.9, (J(117,119Sn,13C)=34.2 Hz), 25.1,
24.0/23.9, ꢀ9.2 ppm (J(117Sn,13C)=316.6, J(119Sn,13C)=331.1 Hz); IR
(CsI): n˜ =1678 cmꢀ1 (C=O); elemental analysis calcd (%) for
C17H36N2O3Sn (435.20): C 46.92, H 8.34, N 6.44; found: C 47.16, H 8.77,
N 6.41.
3-[(Methylthio)methoxy]-1-(trimethylstannanyl)propyl 2,2,4,4-tetrameth-
yl-1,3-oxazolidine-3-carboxylate (12i): Following the general procedure
with 100 mol% of sBuLi, 11i-H (335 mg, 1.15 mmol) afforded 12i
(410 mg, 78%) as a colorless oil. 1H NMR (250 MHz, CDCl3, rotamers):
d=4.62 (m, 1H), 4.61 (s, 2H), 3.71 (s, 2H), 3.60 (m, 2H), 2.14 (m, 2H),
2.13 (s, 3H), 1.53 (brs, 6H), 1.39 and 1.36 (2s, 6H), 0.10 ppm (s,
3-Methoxy-1-(trimethylstannanyl)propyl 2,2,4,4-tetramethyl-1,3-oxazoli-
dine-3-carboxylate (12d): Compound 11d-H (886 mg, 3.61 mmol) afford-
ed 12d (1.15 g, 78%) as a colorless oil. 1H NMR (250 MHz, CDCl3, ro-
tamers): d=4.61 (m, 1H), 3.72 (s, 2H), 3.46 (m, 2H), 3.32 (s, 3H), 2.12
(m, 2H), 1.54 and 1.52 (2s, 6H), 1.40 and 1.36 (2s, 6H), 0.09 ppm (s,
J(117,119Sn,1H)=52.6 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers):
d=153.1/152.4, 95.5/94.4, 76.1/75.9, 70.5 (J(117,119Sn,13C)=38.9 Hz), 68.4
(J(117Sn,13C)=431.9, J(119Sn,13C)=448.8 Hz), 60.3/59.3, 58.4, 33.5, 26.3/
26.2, 25.1, 24.0/23.9, ꢀ9.1 ppm (J(117Sn,13C)=322.3, J(119Sn,13C)=
337.2 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=O); elemental analysis calcd (%)
for C15H31NO4Sn (408.13): C 44.14, H 7.66, N 3.43; found: C 44.27, H
7.75, N 3.41.
J
A
117Sn,1H)=51.5,
JACHTREUNG(
119Sn,1H)=53.8 Hz, 9H); 13C NMR (62.9 MHz,
CDCl3, rotamers): d=153.2/152.5, 95.7/94.6, 76.3/76.1, 75.3, 68.2
(J(117Sn,13C)=420.0, J(119Sn,13C)=442.4 Hz), 65.9 (J(117,119Sn,13C)=
42.1 Hz), 60.5/59.5, 33.5, 26.5/26.4, 25.3/25.2, 24.2/24.1, 13.9, ꢀ9.1 ppm
(J(117Sn,13C)=320.5, J(119Sn,13C)=335.6 Hz); IR (CsI): n˜ =1698 cmꢀ1 (C=
O); elemental analysis calcd (%) for C16H33NO4SSn (454.21): C 42.31, H
7.32, N 3.08, S 7.06; found: C 42.61, H 7.53, N 3.41, S 7.08.
3-(Methylthio)-1-(trimethylstannanyl)propyl 2,2,4,4-tetramethyl-1,3-oxa-
zolidine-3-carboxylate (12j): Compound 11j-H (753 mg, 2.88 mmol) af-
forded 12j (1.13 g, 92%) as a colorless oil. 1H NMR (250 MHz, CDCl3,
rotamers): d=4.56 (m, 1H), 3.72 (s, 2H), 2.57 (m, 2H), 2.12 (s, 3H), 2.11
(m, 2H), 1.53 and 1.52 (2s, 6H), 1.40 and 1.36 (2s, 6H), 0.12 ppm (s,
J
A
117Sn,1H)=51.5,
JACHTREUNG(
119Sn,1H)=53.7 Hz, 9H); 13C NMR (62.9 MHz,
4-Methoxy-1-(trimethylstannanyl)butyl
2,2,4,4-tetramethyl-1,3-oxazoli-
CDCl3, rotamers): d=153.0/152.3, 95.6/94.4, 76.1/75.9, 70.3 (J(117Sn,13C)=
414.7, J(119Sn,13C)=433.8 Hz), 60.3/59.3, 33.4, 32.4 (J(117,119Sn,13C)=
46.7 Hz), 26.5/26.4, 25.3, 25.2, 25.1, 24.0/23.9, 15.4, ꢀ9.2 ppm
(J(117Sn,13C)=320.8, J(119Sn,13C)=335.3 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=
O); elemental analysis calcd (%) for C15H31NO3SSn (424.19): C 42.47, H
7.37, N 3.30, S 7.56; found: C 42.78, H 7.09, N 3.27, S 7.43.
dine-3-carboxylate (12e): Compound 11e-H (600 mg, 2.31 mmol) afford-
ed 12e (630 mg, 65%) as a colorless oil. 1H NMR (250 MHz, CDCl3, ro-
tamers): d=4.46 (m, 1H), 3.67 (s, 2H), 3.36 (t, J=6.4 Hz, 2H), 3.28 (s,
3H), 1.86 (m, 2H), 1.62 (m, 2H), 1.49 and 1.47 (2s, 6H), 1.35 and 1.31
(2s, 6H), 0.05 ppm (s,
JAHCTREUN(G JACHTREUGN(
117Sn,1H)=51.3, 119Sn,1H)=53.5 Hz, 9H);
13C NMR (62.9 MHz, CDCl3, rotamers): d=153.2/152.5, 95.6/94.6, 76.2/
76.0, 72.3, 71.5 (J(117Sn,13C)=426.9, J(119Sn,13C)=446.9 Hz), 60.3/59.4,
58.4, 30.3, 28.0 (J(117,119Sn,13C)=36.2 Hz), 26.5/26.4, 25.3, 24.1/24.0,
ꢀ9.3 ppm (J(117Sn,13C)=317.1, J(119Sn,13C)=331.9 Hz); IR (CsI): n˜ =
1679 cmꢀ1 (C=O); elemental analysis calcd (%) for C16H33NO4Sn
(422.15): C 45.52, H 7.88, N 3.32.; found: C 45.82, H 8.03, N 3.21.
2-(1,3-Dioxolan-4-yl)-1-(trimethylstannanyl)ethyl 2,2,4,4-tetramethyl-1,3-
oxazolidine-3-carboxylate (12k): Following the general procedure with-
out TMEDA, 11k-H (380 mg, 1.39 mmol) afforded 12k (390 mg, 64%)
1
as a colorless oil. H NMR (250 MHz, CDCl3, rotamers): d=5.03 (s, 1H),
4.86 (s, 1H), 4.59 (dd, J=5.2, 9.0 Hz, 1H), 4.14 (m, 1H), 4.01 (m, 1H),
3.72 (s, 2H), 3.54 (m, 1H), 2.23 (m, 1H), 2.00 (m, 1H), 1.54 and 1.52 (2s,
3-(Methoxymethoxy)-1-(trimethylstannanyl)propyl
2,2,4,4-tetramethyl-
6H), 1.40 and 1.36 (2s, 6H), 0.12 ppm (s, JACHRTENUG( ACHTREUNG(
117Sn,1H)=51.8, J 119Sn,1H)=
1,3-oxazolidine-3-carboxylate (12 f): Compound 11 f-H (309 mg,
1.12 mmol) afforded 12 f (450 mg, 92%) as a colorless oil. 1H NMR
(250 MHz, CDCl3, rotamers): d=4.62 (m, 1H), 4.61 (s, 2H), 3.72 (s, 2H),
3.61 (q, J=6.1 Hz, 2H), 3.35 (s, 3H), 2.15 (m, 2H), 1.54 and 1.52 (2s,
54.0 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=152.9/152.2,
95.5/94.3, 94.6, 76.0/75.7, 74.1 (J(117,119Sn,13C)=38.5 Hz), 69.1, 68.0
(J(117Sn,13C)=427.0, J(119Sn,13C)=436.1 Hz)/67.9 (J(117Sn,13C)=421.5,
J(119Sn,13C)=430.2 Hz), 60.3/59.2, 36.7, 26.3/26.2, 25.0/24.9, 23.9/23.8,
ꢀ9.1 ppm (J(117Sn,13C)=324.5, J(119Sn,13C)=339.4 Hz); IR (CsI): n˜ =
1679 cmꢀ1 (C=O); elemental analysis calcd (%) for C16H31NO5Sn
(436.14): C 44.06, H 7.16, N 3.21; found: C 44.10, H 7.11, N 3.12.
6H), 1.40 and 1.36 (2s, 6H), 0.11 ppm (s, JACHRTENUG( ACHTREUNG(
117Sn,1H)=51.7, J 119Sn,1H)=
53.6 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotamers): d=153.0/152.3,
96.2, 95.5/94.4, 76.1/75.9, 68.1 (J(117Sn,13C)=427.6, J(119Sn,13C)=
445.7 Hz), 65.3 (J(117,119Sn,13C)=41.8 Hz), 60.3/59.3, 54.9, 33.5, 26.4/26.3,
25.1/25.0, 24.0/23.9, ꢀ9.2 ppm (J(117Sn,13C)=321.7, J(119Sn,13C)=
336.2 Hz); IR (CsI): n˜ =1678 cmꢀ1 (C=O); elemental analysis calcd (%)
2-(2,2-Dimethyl-1,3-dioxan-4-yl)-1-(trimethylstannanyl)ethyl 2,2,4,4-tetra-
methyl-1,3-oxazolidine-3-carboxylate (12m): Following the general proce-
2286
www.chemeurj.org
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2277 – 2289

Organolithium Compounds
FULL PAPER
dure without TMEDA, 11m-H (403 mg, 1.28 mmol) afforded 12m
(470 mg, 77%) as a colorless oil. 1H NMR (250 MHz, CDCl3, rotamers):
d=4.52 (m, 1H), 3.98–3.65 (m, 3H), 3.60 (s, 2H), 1.90 (m, 2H), 1.49 (m,
2H), 1.41 (s, 6H), 1.31, 1.29 and 1.25 (3s, 12H), ꢀ0.01 and ꢀ0.02 ppm
(2s, J(117,119Sn,1H)=52.7 Hz, 9H); 13C NMR (62.9 MHz, CDCl3, rotam-
ers): d=152.9/152.2, 98.1/98.0, 95.5/94.3, 76.0/75.8, 67.5 (J(117Sn,13C)=
432.8, J(119Sn,13C)=449.0 Hz)/67.0 (J(117Sn,13C)=427.7, J(119Sn,13C)=
444.6 Hz), 66.6/66.4, 60.2/59.2, 59.6, 40.5/40.2, 31.5/30.6, 29.7/29.6, 26.3/
26.2, 25.1/25.0, 24.0/23.9, 18.9/18.8, ꢀ8.9 (J(117Sn,13C)=321.5,
J(119Sn,13C)=336.9 Hz), ꢀ9.1 ppm (J(117Sn,13C)=319.4, J(119Sn,13C)=
338.4 Hz); IR (CsI): n˜ =1679 cmꢀ1 (C=O); elemental analysis calcd (%)
for C19H37NO5Sn (478.22): C 47.72, H 7.80, N 2.93; found: C 47.36, H
8.02, N 2.91.
cooled (ꢀ788C) solution of 13b-H (250 mg, 1.00 mmol) and TMEDA
(165 mL, 1.10 mmol) in Et2O (4.6 mL). After stirring for 30 min, Me3SnCl
(1.1 mL, 1.1 mmol, 1.0m in THF) was added to the reaction mixture. The
resulting solution was stirred at ꢀ788C for 30 min and then partitioned
between Et2O (10 mL) and pH 7.0 phosphate buffer (10 mL). The aque-
ous phase was extracted with Et2O (10 mL) and the combined organic
phase was washed with brine (10 mL), dried with Na2SO4, filtered and
concentrated. The residue was purified by column chromatography
(grade III neutral Al2O3, hexane to EtOAc/hexane 1:50). Recrystalliza-
tion from EtOH gave 14b as a white solid (392 mg, 95%). M.p. 44–478C;
1H NMR (300 MHz, CDCl3, rotamers): d=7.17 (t, J=7.7 Hz, 1H), 6.91
(m, 3H), 5.58 (s, J(117,119Sn,1H)=25.0 Hz, 1H), 4.24–3.72 (brm, 2H), 2.32
(s, 3H), 1.24 (d, J=6.1 Hz, 12H), 0.02 ppm (s,
119Sn,1H)=53.6 Hz, 9H); 13C NMR (75 MHz, CDCl3, rotamers): d=
JACHTREUNG(
117Sn,1H)=51.5,
JACHTREUNG(
3-Methylbenzyl N,N-diisopropylcarbamate (13b-H): A solution of diiso-
propylcarbamyl chloride (600 mg, 3.67 mmol) in pyridine (360 mL,
4.40 mmol) was treated with 3-methylbenzyl alcohol (420 mL, 3.50 mmol)
and stirred at 1058C for 16 h in a sealed tube. The reaction mixture was
cooled and then partitioned between 2m HCl (10 mL) and Et2O (3”
10 mL), and the combined organic phase was washed with satd aq
NaHCO3 (15 mL) and brine (15 mL), dried with Na2SO4, filtered and
concentrated. The resulting residue was purified by column chromatogra-
phy (silica gel, EtOAc/hexane 1:10) to give 13b-H (663 mg, 76%) as a
colorless oil. 1H NMR (300 MHz, CDCl3, 330 K): d=7.27–7.08 (m, 4H),
5.15 (s, 2H), 3.98 (sept, J=6.7 Hz, 2H), 2.38 (s, 3H), 1.26 ppm (d, J=
6.7 Hz, 12H); 13C NMR (75 MHz, CDCl3, 330 K, rotamers): d=154.8,
137.3, 136.8, 128.1, 128.0, 127.8, 124.5, 65.9, 45.6, 20.8, 20.6 ppm; IR
(CsI): n˜ =1695 cmꢀ1 (C=O); elemental analysis calcd (%) for C15H23NO2
(249.36): C 72.25, H 9.30, N 5.62; found: C 71.89, H 9.46, N 5.57.
155.9 (J(117,119Sn,13C)=14.1 Hz), 143.0 (J(117,119Sn,13C)=14.1 Hz), 137.7
(J(117,119Sn,13C)=9.9 Hz),
(J(117,119Sn,13C)=12.5 Hz),
(J(117,119Sn,13C)=18.3 Hz),
128.2
124.2
74.0
(J(117,119Sn,13C)=9.9 Hz),
(J(117,119Sn,13C)=18.8 Hz),
125.6
120.7
(J(117Sn,13C)=384.6,
J(119Sn,13C)=
401.8 Hz), 46.3/45.3, 21.5, 21.4/20.6, ꢀ9.0 ppm (J(117Sn,13C)=320.3,
J(119Sn,13C)=335.5 Hz); IR (CsI): n˜ =1675 cmꢀ1 (C=O); elemental analy-
sis calcd (%) for C18H31NO2Sn (412.16): C 52.45, H 7.58, N 3.40; found:
C 52.55, H 7.63, N 3.36.
(3-Methoxyphenyl)-(trimethylstannanyl)methyl
N,N-diisopropylcarba-
mate (14c): Same procedure as for 14b but starting with 13c-H (265 mg,
1.00 mmol) afforded 14c (325 mg, 76%) as a white solid after purification
by column chromatography (grade III neutral Al2O3, hexane to EtOAc/
hexane 1:20) and recrystallization from EtOH. M.p. 52–538C; 1H NMR
(300 MHz, CDCl3, rotamers): d=7.20 (t, J=8.2 Hz, 1H), 6.66 (m, 3H),
5.60 (s, J(117,119Sn,1H)=25.3 Hz, 1H), 4.21–3.70 (brm, 2H), 3.78 (s, 3H),
3-Methoxybenzyl N,N-diisopropylcarbamate (13c-H): Same procedure as
for 13b-H but starting with 3-methoxybenzyl alcohol (440 mL, 3.50 mmol)
afforded 13c-H (698 mg, 75%) as a colorless oil after column chromatog-
1.26 (brs, 12H), 0.03 ppm (s,
JAHCTREUN(G JACHTREUGN(
117Sn,1H)=51.5, 119Sn,1H)=53.6 Hz,
9H); 13C NMR (75 MHz, CDCl3, rotamers): d=159.5 (J(117,119Sn,13C)=
10.5 Hz), 155.6 (J(117,119Sn,13C)=14.6 Hz), 144.8 (J(117,119Sn,13C)=13.6 Hz),
129.2 (J(117,119Sn,13C)=9.9 Hz), 115.8 (J(117,119Sn,13C)=18.3 Hz), 110.0
1
raphy (silica gel, EtOAc/hexane 1:8). H NMR (300 MHz, CDCl3, 330 K):
d=7.24 (t, J=7.6 Hz, 1H), 6.94 (m, 2H), 6.83 (m, 1H), 5.12 (s, 2H), 3.94
(sept, J=6.7 Hz, 2H), 3.79 (s, 3H), 1.23 ppm (d, J=6.7 Hz, 12H);
13C NMR (75 MHz, CDCl3, 330 K, rotamers): d=159.5, 155.3, 138.6,
129.3, 119.9, 113.2, 113.0, 66.2, 55.0, 45.9, 20.9 ppm; IR (CsI): n˜ =
1693 cmꢀ1 (C=O); elemental analysis calcd (%) for C15H23NO3 (265.35):
C 67.90, H 8.74, N 5.28; found: C 68.13, H 8.61, N 5.17.
(J(117,119Sn,13C)=12.5 Hz),
108.9
(J(117,119Sn,13C)=18.3 Hz),
73.8
(J(117Sn,13C)=378.3, J(119Sn,13C)=396.1 Hz), 54.8, 46.2/45.3, 21.3/20.5,
ꢀ9.0 ppm (J(117Sn,13C)=321.9, J(119Sn,13C)=337.1 Hz); IR (CsI): n˜ =
1791 cmꢀ1 (C=O); elemental analysis calcd (%) for C18H31NO3Sn
(428.16): C 50.49, H 7.30, N 3.27; found: C 50.70, H 7.20, N 3.06.
4-Methoxybenzyl N,N-diisopropylcarbamate (13d-H): Same procedure as
for 13b-H but starting with 4-methoxybenzyl alcohol (550 mg,
3.98 mmol) afforded 13d-H (845 mg, 80%) as a colorless oil after column
chromatography (silica gel, EtOAc/hexane 1:8). 1H NMR (300 MHz,
CDCl3, 330 K): d=7.25 (d, J=8.6 Hz, 2H), 6.84 (d, J=8.6 Hz, 2H), 5.03
(s, 2H), 3.88 (sept, J=6.6 Hz, 2H), 3.76 (s, 3H), 1.18 ppm (d, J=6.6 Hz,
12H); 13C NMR (75 MHz, CDCl3, 330 K, rotamers): d=159.1, 155.1,
129.2, 129.1, 113.6, 65.9, 54.9, 45.8, 20.9 ppm; IR (CsI): n˜ =1691 cmꢀ1 (C=
O); elemental analysis calcd (%) for C15H23NO3 (265.35): C 67.90, H
8.74, N 5.28; found: C 68.09, H 8.94, N 5.28.
(4-Methoxyphenyl)-(trimethylstannanyl)methyl
N,N-diisopropylcarba-
mate (14d): Same procedure as for 14b but starting with 13d-H (265 mg,
1.00 mmol) afforded 14d (381 mg, 89%) as a white solid after purifica-
tion by column chromatography (grade III neutral Al2O3, hexane to
EtOAc/hexane 1:20) and recrystallization from EtOH. M.p. 56–588C;
1H NMR (300 MHz, CDCl3, 330 K, rotamers): d=7.05 (d, J=8.8 Hz,
2H), 6.84 (d, J=8.8 Hz, 2H), 5.55 (s, J(117,119Sn,1H)=22.0 Hz, 1H), 3.97
(sept, J=6.6 Hz, 2H), 3.80 (s, 3H), 1.28 and 1.26 (2 d, J=6.6 Hz, 12H),
0.06 ppm (s,
JAHCTREUN(G JACHTREUGN(
117Sn,1H)=51.3, 119Sn,1H)=53.5 Hz, 9H); 13C NMR
(75 MHz, CDCl3, 330 K, rotamers): d=157.3, 155.9, 135.4/135.3, 125.35
(J(117,119Sn,13C)=20.4 Hz)/125.32 (J(117,119Sn,13C)=20.1 Hz), 113.93/113.90
(J(117,119Sn,13C)=8.9 Hz), 73.9/73.8 (J(117Sn,13C)=398.9, J(119Sn,13C)=
420.7 Hz), 55.31/55.28, 46.1, 21.2/21.1, ꢀ8.7 ppm (J(117Sn,13C)=318.7,
J(119Sn,13C)=339.6 Hz); IR (CsI): n˜ =1674 cmꢀ1 (C=O); elemental analy-
sis calcd (%) for C18H31NO3Sn (428.16): C 50.49, H 7.30, N 3.27; found:
C 50.42, H 7.61, N 3.27.
1-Phenylethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-3-carboxylate (13e-H):
A suspension of NaH (60% in mineral oil, 410 mg, 10.3 mmol) in THF
(12 mL) was treated with 1-phenyl-ethanol (830 mL, 6.90 mmol), the mix-
ture was stirred at RT for 30 min and 2,2,4,4-tetramethyl-1,3-oxazolidine-
3-carbonyl chloride[27] (1.57 g, 8.20 mmol) in THF (2 mL) was added. The
mixture was stirred at RT for 5 d and then poured over 2m HCl solution
(15 mL) and extracted with EtOAc (3”20 mL). The combined organic
phase was washed with satd aq NaHCO3 (30 mL) and brine (30 mL),
dried with Na2SO4, filtered and concentrated. The resulting residue was
purified by column chromatography (silica gel, EtOAc/hexane 1:8) to
give 13e-H as a colorless oil (1.85 g, 97%). 1H NMR (300 MHz, CDCl3,
rotamers): d=7.25 (m, 5H), 5.80 (q, J=6.6 Hz, 1H), 3.68 (s, 2H), 1.57,
1.54, 1.53, 1.51, 1.46, 1.41, 1.40, 1.32 ppm (8s, 15H); 13C NMR (75 MHz,
CDCl3, rotamers): d=152.0/151.2, 142.2/142.1, 128.4, 127.5, 125.9, 95.8/
94.7, 76.3/76.0, 72.7, 60.6/59.6, 26.7/26.6, 25.5/25.4, 25.3/25.2, 24.1, 22.5/
22.4 ppm; IR (CsI): n˜ =1698 cmꢀ1 (C=O); elemental analysis calcd (%)
for C16H23NO3 (277.37): C 69.29, H 8.36, N 5.05; Found: C 69.48, H 8.60,
N 5.11.
1-Phenyl-1-(trimethylstannanyl)ethyl 2,2,4,4-tetramethyl-1,3-oxazolidine-
3-carboxylate (14e): Following the general procedure of stannylation but
stirring only for 1 h after addition of sBuLi, 13e-H (579 mg, 2.09 mmol)
gave 14e (816 mg, 89%) as a white solid after recrystallization from
MeOH. M.p. 89–908C; 1H NMR (300 MHz, CDCl3, rotamers): d=7.31
(t, J=7.6 Hz, 2H), 7.10 (m, 3H), 3.77 (s, 2H), 1.84 and 1.83 (2s,
J(117,119Sn,1H)=49.9 Hz, 3H), 1.64, 1.61, 1.58, and 1.56 (4s, 6H), 1.49,
1.47, 1.45, and 1.39 (4s, 6H), ꢀ0.02 ppm (s, J(117,119Sn,1H)=51.5 Hz, 9H);
13C NMR (75 MHz, CDCl3, rotamers): d=153.5/152.8, 147.8, 128.1
(J(117,119Sn,13C)=8.8 Hz), 124.9 (J(117,119Sn,13C)=9.4 Hz), 123.3/123.2, 95.8/
94.9, 79.8, 76.4/76.1, 60.7/59.9, 26.8/26.7, 25.9/25.6, 25.2, 25.1, 24.2,
ꢀ6.9 ppm (J(117Sn,13C)=329.2, J(119Sn,13C)=346.6 Hz); IR (CsI): n˜ =
1666 cmꢀ1 (C=O); elemental analysis calcd (%) for C19H31NO3Sn
(440.17): C 51.85, H 7.10, N 3.18; found: C 51.63, H 7.13, N 3.16.
(3-Methylphenyl)-(trimethylstannanyl)methyl N,N-diisopropylcarbamate
(14b): BuLi (690 mL, 1.10 mmol, 1.6m in hexane) was added to a pre-
Chem. Eur. J. 2007, 13, 2277 – 2289
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2287

F. J. Sardina et al.
NMR Spectroscopy
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mol% of a solution of MeLi in Et2O (1.5m) or Bu6Li in pentane was
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organostannane in dry [D8]THF (250 mL) was added and the NMR tube
was sealed under a high pressure of Ar.
Acknowledgements
Financial support from the MCYT and MEC (Spain, grants BQU2002-
01368 and CTQ2006-07854/BQU and fellowships to P.M. and P.G.) and
the Xunta de Galicia (grant PGIDIT03PXIC20910PN) is gratefully ac-
knowledged.
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Chem. Eur. J. 2007, 13, 2277 – 2289

Organolithium Compounds
FULL PAPER
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Received: June 20, 2006
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Published online: December 13, 2006
Chem. Eur. J. 2007, 13, 2277 – 2289
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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