Synthesis of new mixed (-)-menthylalkyltin dihydrides. stereoselective reduction of chiral and prochiral ketones

Article abstract of DOI:10.1016/j.jorganchem.2021.121680

This paper reports de synthesis of a series of (-)-menthylalkyltin dihydrides, (-)-MenRSnH₂ (R = Me, n-Bu, i-Pr, t-Bu, Neophyl), starting from (-)-menthyltrimethyltin. The new (-)-menthylalkyltin dihydrides 12–16 were used in a study on the stereoselective reduction of chiral (-)-menthone under different reaction conditions. Also the results obtained in the reductions of prochiral acetophenone (27) and 2-acetylnaphthalene (28), with (-)-menthylmethyl- (12) and (-)-menthyli-propyltin (14) dihydrides are informed. Some physical properties as well as full ¹H-, ¹³C-, and ¹¹⁹Sn NMR data of the new organotin compounds are informed.

Full text of DOI:10.1016/j.jorganchem.2021.121680

Journal of Organometallic Chemistry 935 (2021) 121680
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of new mixed (-)-menthylalkyltin dihydrides. stereoselective
reduction of chiral and prochiral ketones
V. Fabricio Terraza a,b, Darío C. Gerbinoa,c, Julio C. Podestáa,∗
a INQUISUR, Departamento de Química, Universidad Nacional del Sur (UNS)-CONICET, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
b Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC-PBA), Calle 526 entre 10 y 11, B1900 La Plata, Argentina
c Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB Ciudad Autónoma de Buenos Aires, Argentina
a r t i c l e i n f o
a b s t r a c t
Article history:
This paper reports de synthesis of a series of (-)-menthylalkyltin dihydrides, (-)-MenRSnH2 (R = Me, n-
Bu, i-Pr, t-Bu, Neophyl), starting from (-)-menthyltrimethyltin. The new (-)-menthylalkyltin dihydrides
12–16 were used in a study on the stereoselective reduction of chiral (-)-menthone under different
reaction conditions. Also the results obtained in the reductions of prochiral acetophenone (27) and 2-
acetylnaphthalene (28), with (-)-menthylmethyl- (12) and (-)-menthyli-propyltin (14) dihydrides are in-
formed. Some physical properties as well as full 1H-, 13 C-, and 119 Sn NMR data of the new organotin
compounds are informed.
Received 9 November 2020
Revised 1 January 2021
Accepted 2 January 2021
Available online 5 January 2021
Key words:
(-)-menthylalkyltin dihydrides
Use in stereoselective reductions
Reduction of (-)-menthone
Reduction of acetophenone, Reduction of
2-acetylnaphthalene
© 2021 Elsevier B.V. All rights reserved.
1. Introduction
mixed alkyl and (-)-menthyl organic ligands have been reported
[7].
Among the organometallic compounds of Group 14 elements,
the organosilicon and organotin derivatives are the more used be-
cause of the wide range of chemical reactions they can undergo. In
addition, organotin and organosilicon compounds have lower costs
and toxicities compared with those of the corresponding deriva-
tives of germanium and lead respectively. Nowadays, the enantios-
elective reduction of ketones is one of the more exciting fields
in development. Thus, the hydrosilylation of ketones has been
achieved with remarkable high enantioselectivities carrying out the
reactions with organosilanes (Me2SiHCl, Ph2SiH2, PhSiH3, and oth-
ers) in the presence of transition metals like Fe [1], and Rh [2] con-
taining chiral organic ligands.
On the other hand, there are fewer reports on the uses of
diorganotin dihydrides (R2SnH2), mostly restricted to the use of
Ph2SnH2 and n-Bu2SnH2 as reagents for the reduction of car-
bonyl compounds. We have not found reports on the synthesis of
diorganotin dihydrides containing mixed alkyl and (-)-menthyl lig-
ands.
In this paper we wish to report the synthesis of mixed diorgan-
otin dihydrides containing a bulky chiral (-)-menthyl substituent
and alkyl groups of increasing steric volumes. We also report the
results obtained in the reductions of chiral and prochiral ketones
with the new (-)-menthylalkyltin dihydrides.
2. Results and discussion
Organotin hydrides have found many uses in organic synthe-
sis not only as reducing reagents [3], but also as intermediates in
the generation of carbon-carbon bonds [4], and in the synthesis of
macrocycles via cyclohydrostannation [5]. Since one of the semi-
nal papers on the reduction of carbonyl compounds with mono-,
di-, and triorganotin hydrides was published in 1961 [6], mainly
the triorganotin hydrides (R3SnH) have been used routinely for the
selective free radical reduction of alkyl halides and many other
functional groups [3,4]. At present triphenyl- and tri-n-butyltin hy-
drides are commercially available. Triorganotin hydrides containing
The synthesis of the new organotins was carried out taking
into account the reported sequence for the easy of brominolysis
of carbon-tin bonds in tetraalkyltins [8]:
Ph > Me > Et > Pr > n − Bu > sec − Pr > tert − Bu
The new diorganotin dihydrides were obtained according
to Scheme 1. The starting organotin compound containing
the optically pure (-)-menthyl ligand was the known (-)-
menthyltrimethyltin (1), obtained by stereospecific alkylation of
trimethyltin chloride with (-)-menthylmagnesium chloride. Bromi-
nolysis of compound 1 in methanol using 1 equiv of bromine af-
fords the also known (-)-menthyldimethyltin bromide (2) [7]. On
∗
Corresponding author.
E-mail address: jpodesta@uns.edu.ar (J.C. Podestá).
https://doi.org/10.1016/j.jorganchem.2021.121680
0022-328X/© 2021 Elsevier B.V. All rights reserved.

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
Scheme 1. Synthesis of diorganotin dihydrides 12–16.
the other hand, the brominolysis of 1 with 2.5 equiv of bromine
led to the corresponding (-)-menthylmethyltin dibromide (3) in
75% yield [9].
stannyl group. On the other hand, the values in the range 20–23 Hz
found for the 3J(C,Sn) coupling constants of C-8 suggest a dihedral
angle of around 60° with respect to the organostannyl substituent.
From the previous discussion it is possible to conclude that in
these compounds the organotin moiety occupies an equatorial po-
sition in the cyclohexane ring of the (-)-menthyl group. These re-
sults are in agreement with those obtained by Schumann et al.
[10].
Then, the alkylation of (-)-menthyldimethyltin bromide
2
with n-butylmagnesium bromide, i-propyl magnesium bro-
mide, t-butylmagnesium bromide, and neophylmagnesium
bromide enabled the synthesis of the corresponding (-)-
menthylalkyldimethyltin derivatives 4–7 in average yields of
82%. The reaction of tetraorganotin compounds 4, 5, and 7 with
2.5 equiv of bromine in methanol led to dibromides 8, 9, and 11
respectively. On the other hand, we were able to obtain t–butyl(-
)menthyltin dibromide (10) in only a 30% yield; it is to note that
the reported yield for this reaction is 58% [10].
The 13C NMR spectrum of compound 14 shows more than one
ꢀ
resonance for carbons C-1 and C-1 . This multiplicity of signals
could be connected with the steric crowding rather than with any
effect of the chiral menthyl ligand, as shown in previous investiga-
tions of our group [13,14].
Dibromides 3, and 8–11 were reduced with LiAlH4 in di-
ethyl ether at room temperature (rt) in the dark, leading to
the corresponding (-)-menthylalkyltin dihydrides 12–16 in aver-
age yields above 90%. In Scheme 1, besides dihydrides 12–16,
Dihydrides 12–16 are dense and, most of them, colorless oils.
We attempted to determine the relative stabilities of the dihy-
drides. This was done by leaving the (-)-menthylalkyltin dihydrides
12–16 in the dark, at rt, and in the open air (Scheme 2), and mea-
(-)-menthylalkyldimethyltin compounds
4
and 7, and also (-)-
suring the times needed for the ν
band to disappear in the
Sn-H
menthylalkyltin dibromides 8, 9, and 11 have not been reported
previously. 119 Sn and 13C NMR spectra of diorganotin diahydrides
12–16 are summarized in Table 1. It should be noted that in a
previous communication we have reported the synthesis of some
of the compounds included in Scheme 1 following less convenient
synthetic routes and giving only some NMR selected values [11].
The 13C NMR spectra of these compounds (Table 1), showed
that all of them were obtained without epimerization at the men-
thyl carbon directly attached to tin [C(1)] atom. In all cases, the
10 carbon resonances of the menthyl group were clearly distin-
guishable. The DEPT experiments together with the magnitude of
the nJ(13C,119 Sn) coupling constants |1J| > |3J| > |2J| > |4J| enabled
the easy assignment of the signals, and, therefore, to establish the
structure of the new compounds. The use of the Karplus-type rela-
tionship existing between the value of the 3J(C, Sn) coupling con-
stants and the dihedral angle [12] allowed us to deduce the stere-
ochemistry of the (-)-menthy1 ligands. Thus, the 3J(C,Sn) values in
the range 60–73 Hz for carbons C-3 and C-5 of the (-)-menthyl
group in all the compounds included in Table 1, indicate dihedral
angles of ca. 180° between these carbons and the tin moiety at-
tached to C-1, i.e., anti positions with respect to the dihydroalkyl-
FT-IR spectra. We found that whereas the decomposition at rt of
dihydrides 12 and 13 takes 14 h, dihydrides 14–16 were still active
after five weeks.
The reduction of ketones with diorganotin dihydrides proceeds
according to Scheme 2. An interesting feature of the reduction
with diorganotin dihydrides is that the two atoms of hydrogen are
transferred to the substrate directly, i.e., these reactions avoid the
formation of intermediate alkoxides. Therefore, a hydrolysis step
and acidic or basic conditions are not needed. This could be im-
portant in the reduction of certain types of sensitive compounds.
It should be added that the reduction of the polydialkylstannanes
(P) obtained in the reduction of the ketones led to the diorganotin
dihydrides in average yields of 48%.
In order to test possible uses in asymmetric transformations,
we considered it of interest to carry out a study on the reduction
of (-)-menthone (22) with dihydrides 12–16. The reduction of 22
should lead to a mixture of (-)-menthol (24), the thermodynami-
cally more stable diastereomer (three equatorial substituents), and
(+)-neomenthol (25), the less stable diastereomer (two equatorial
substituents) (see scheme included in Table 2). Taking into account
that the (-)-menthone (22) used in our studies consisted of a mix-
2

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
Table 1
13 C- and 119 Sn-NMR characteristics, and optical rotations of (-)-menthylalkyltin dihydrides 12–16.
a
c
d
e
f
g
Comp. 12
Comp. 13
Comp. 14
Comp. 15
Comp. 16
δ-C-1 (1 J)
δ-C-2 (2 J)
δ-C-3 (3Jtrans
δ-C-4 (4 J)
δ-C-5 (3Jtrans
δ-C-6 (2 J)
δ-C-7
31.29 (439.5)
47.70 (17.2)
26.83 (66.1)
35.79 (NO)
35.55 (72.2)
42.59 (19.3)
22.70
31.89 (416.9)
47.89 (17.1))
26.89 (65.2)
35.85 (7.3)
35.68 (71.4)
43.13 (18.3)
22.72
32.72 (396.4)
47.86 (17.2)
26.95 (62.7)
35.86 (8.0)
35.75 (67.5)
43.47 (18.8)
22.71
33.90 (382.0)
47.58 (16.7)
26.92 (60.1)
35.83 (NO)
35.80 (68.1)
43.89 (18.5)
22.75
31.69 (422.3)
47.57 (17.9)
26.83 (64.8)
35.80 (7.1)
35.58 (72.9)
42.81 (17.9)
22.70
)
)
δ-C-8 (3Jgauche
)
33.84 (23.2)
22.12
34.04 (21.0)
22.17
34.23 (21.4)
22.17
34.21 (20.8)
22.15
33.67 (23.0)
22.12
δ-C-9
δ-C-10
15.57
15.63
15.68
15.73
15.60
ꢀ
ꢀ
ꢀ
1
2
3
δ-C-1
δ-C-2
δ-C-3
(
(
(
J)
J)
J)
−15.51 (328.0)
—
7.27 (353.6)
31.12 (23.7)
27.35 (58.1)
13.78 (393.1)
23.79 (14.4))
—
25.78 (NO)
32.63 (NO)
—
27.52 (353.2)
37.56 (21.0)
32.18 (34.3) 32.49 (36.0)
—
119Sn
[α]2D0(c,bbenzene)
−204
−191
−159
−144
−223
−32.5° (0.0278)
−32.5° (0.0278)
−31.55° (0.0773)
−23.8° (0.0230)
−29.8° (0.0636)
a
In C6D6; chemical shifts (δ) in ppm with respect to the central peak of C6D6
stants nJ(119 Sn,13 C) in Hz (in brackets); NO = not observed.b In gr/mL.
(
13 C NMR) and Me4Sn (119 Sn-NMR);coupling con-
c
Other signals: 119 Sn NMR: 1J(Sn,H) 1346 Hz; 1J(Sn,C) 456.2 Hz.
d
Other signals 119 Sn NMR: 1J(Sn,H) 1384 Hz; 1J(Sn,C) 460,3 Hz; 13 C NMR: 1J(Sn,C) 13,92 Hz.
Other signals: 119 Sn NMR::1J(Sn,H) 1326 Hz; 1J(Sn,C) 463.4 Hz.
Other signals: 119 Sn NMR: 1J(Sn,H) 1391 Hz; 1J(Sn,C) 466.0 Hz.
e
f
g
Other signals: 119 Sn NMR: 1J(Sn,H) 1384 Hz; 1J(Sn,C) 460,3 Hz; 13 C NMR: 125,63; 126,06; 128,52; 150,90.
Scheme 2. Reduction of ketones with diorganotin dihydrides.
ture of 22 (95%) and (+)-isomenthone (23) (5%), the crude mixture
of reduction products should also contain (-)-neoisomenthol (26)
the product of the reduction of (+)-isomenthone (23). The mixture
of 22 (95%) and (+)-isomenthone (23) (5%) used in the studies will
be referred to as Mix-22–23 from here onwards.
in higher proportion than 25 (1S) the diastereomer ratio is repre-
sented in the scheme of Table 2 as dr I. When 25 was in higher
proportion than 24 the ratio is represented as dr II.
The reduction of Mix-22–23 with (-)-menthylmethyltin dihy-
dride (12) was done without solvent and also in solution in sev-
eral solvents (Table 2, entries 3–8). Thus, the FT-IR spectrum of
the reduction of Mix-22–23 with dihydride 12, carried out with-
out solvent, after 3 h reaction at rt showed that the νSn-H band
corresponding to 12 had disappeared (Table 2, entry 3). The to-
tal yield of reduction products 24–26 was 78.8%. Some unreacted
starting ketones 22 and 23 (16.7 and 4.4% respectively) were still
present in the crude product. The diastereomeric ratio drI = 1.69,
indicates that the more stable diastereomer 24 was obtained in
lower proportion than in the case of the reduction with n-Bu2SnH2
(Table 2, entry 2). The same mixture after 6 h of reaction at −75 °C
(Table 2, entry 4) gave the products of reduction 24–26 in quanti-
tative yields. However, in this case the drI = 1.0 indicates that the
diastereomer 24 and 25 were formed in approximately the same
proportion.
It has been reported that the reduction of pure (-)-menthone
(22) with LiAlH4 leads to a mixture of menthol, neomenthol and
neoisomenthol in a ratio = 71 / 27 / 2 respectively [15]. A similar
ratio for the mixture of alcohols 24, 25, and 26 (72 / 27 / 1) was
reported more recently [16].This ratio should reflect the asymmet-
ric induction exerted by the two stereocenters already present in
(-)-menthone (22), and it also suggests that there is some isomer-
ization of 22 to 23 before reduction takes place. We carried out
the reduction of Mix-22–23 with LiAlH4 in ether and found a ratio
24 (68) / 25 (27) / 26 (5) (Table 2, entry 1).
The reduction of (-)-menthone (22) with n-Bu2SnH2 was first
reported in 1961 [4]. Unfortunately, the authors only reported the
yield of the reaction (81.5%) but not the relationship among the di-
astereomers in the crude mixture of reaction. We reduced Mix-22–
23 with n-Bu2SnH2 in ether (Table 2, entry 2) and found a propor-
tion 24 (65%), 25 (31%), and 26 (4%), i.e., similar to that obtained
in the reduction with LiAlH4 (Table 2, entry 1).
Then, we studied the effect of using solvents of different po-
larity on the reaction between Mix-22–23 and hydride 12. Using
toluene at rt (Table 2, entry 5) the FT-IR spectrum showed that the
νSn-H band corresponding to 12 disappeared after 14 h of reaction.
The yield of reduction products was 73.8%, but unreacted starting
ketones 22 and 23 were still present in 23% and 3.2% respectively.
The drI = 1.89 indicates that also in this case the more stable di-
astereomer 24 predominates.
Taking into account that we wanted to determine the approx-
imate degree of asymmetric induction that can be achieved using
the new dihydrides, we calculated the diastereomer ratios (dr) be-
tween 24 and 25, i.e., the alcohols resulting from the reduction of
22. In those cases where the more stable diastereomer 24 (1R) was
3

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
Table 2
Reduction of (-)-menthone with chiral diorganotin dihydrides 12–16.a.
Product distribution
Starting
comp.c
Yield (%)d
e
f
g
N°
1
Hydride
Solv.b
Et2O
Et2O
–
Time (h)
0.5
6
24 (%)
68
25 (%)
27
26 (%)
5
24+25 + 26
100
dr I
2.51
2.09
1.69
1.00
1.89
2.27
2.31
1.76
–
dr II
–
de (%)
(%)
–
LiAlH4
41
2
Bu2SnH2
65
31
4
–
100
–
34
3
12
3
47.4
48.7
46.2
50.7
46.9
59.5
28.5
41.4
36.4
26.6
32.9
32.0
38.4
59.2
66.7
36.9
26.2
21.8
27.9
48.5
24.4
22.3
20.3
33.7
68.5
54.4
57.4
68.3
62.1
63.7
58.0
33.4
29.8
59.0
59.1
27.5
3.5
2.8
3.2
3.3
2.7
4.6
3.0
4.2
4.2
5.1
5.0
4.4
3,6
7,6
3,5
4,1
4.9
3.4
22 (16.7) 23 (4.4)
78.8
100
–
19.5
0.2
4
12 (−75 °C)
–
6
–
–
5
12
12
12
12
13
13
13
14
14
14
15
15
15
16
16
16
Toluene
Et2O
THF
MeOH
–
14
14
14
3
22 (23.0) 23 (3.2)
73.8
76.3
69.9
97.8
100
–
21.8
28.4
26.6
25.8
40
6
22 (20.8) 23 (2.8)
–
7
22 (27.6) 23 (2.4)
–
8
22 (1.5) 23 (0.7)
–
9
24
14
12
12
24
12
14
14
3
–
2.40
1.31
1.57
2.56
1.88
1.99
1.51
–
10
11
12
13
14
15
16
17
18
19
20
Et2O
MeOH
–
–
100
–
13
22 (1.9)
98
–
21
–
100
–
41.7
29.2
31.7
19.6
25.8
36.9
22.1
32.9
5.7
Et2O
MeOH
–
–
100
–
–
100
–
–
100
–
Et2O
MeOH
–
–
92,6
100
1.77
2.23
–
–
–
21
70
14
–
100
1.59
2.25
1.26
Et2O
MeOH
22 (9.7) 23 (0.1)
22 (45.6) 23 (1.7)
90,2
52,7
–
a
Yields from GS-MS analysis. Retention times (RT) of Mix-22–23, 6.505 min (22), 6.791 min (23); RT of alcohols, 8208 min (24); 7.798 min (25);
8.109 min (26); the results included in the Table are the average of five reactions; reactions at rt except when otherwise stated.
b
Dry solvents; Tol = toluene; THF = tetrahydrofuran.
c
Starting unreacted compounds (%).
d
Total yields on reduction products (%), 24 + 25 + 26.
e
Diastereomeric ratio, dr I = [24] / [25].
f
dr II = [25] / [24].
g
de = diastereomeric excess = [24]% – [25]% (N° 3–8 and 16–17) and [25]% – [24]% (N° 9–15 and 18–20).
When the reductions were carried out in ether and THF, the
νSn-H band in the IR spectrum corresponding to 12 disappeared af-
ter 14 h reaction (Table 2, entries 6 and 7 respectively). The yields
of the reduction products 76.3% (ether) and 69.9% (THF) were sim-
ilar to those obtained in the reaction in toluene. Also, the observed
drI = 2.27 and 2.31 indicate that in these cases the more stable al-
cohol 24 was formed in higher proportion than in the case of the
reduction of Mix-22–23 with n-Bu2SnH2.
atom favors the formation of the less thermodynamically stable
product 25.
In the case of the reductions of Mix-22–23 using hydrides 13,
14, and 16, in ether (Table 2, entries 10, 13, and 19) the mixtures
(24+25+26) obtained contained the diastereomer 25 as the main
component in quantitative (with dihydrides 13 and 14) and very
high yields (90.2% using dihydride 16). However, when we carried
out the reaction of Mix-22–23 with dihydride 15 in ether the re-
sulting mixture of reduction products was obtained in high yield
(92.6%), containing the thermodynamic diastereomer 24 in higher
proportion.
On the other hand, the reaction of Mix-22–23 with dihydride
12 in methanol (Table 2, entry 8) led to the reduction products
after 3 h reaction, remaining a 2.2% of unreacted ketones 22 and
23. The observed drI = 1.76 indicates that alcohol 24 is formed in
lower proportion than in the case of the less polar solvents.
Taking into account the previous results, the study of the re-
ductions with hydrides 13–16 was performed under three reaction
conditions: without solvent, in ether, and in methanol.
The reactions performed in methanol followed a similar pattern.
Thus the reductions of Mix-22–23 with dihydrides 13, 14, and 16,
led in all cases to the formation of alcohol 25 as the main compo-
nent of the mixtures (24+25+26) (Table 2, entries 11, 14 and 16).
However, whereas the reactions using dihydrides 13 and 14 took
place with very high yields, the reduction of Mix-22–23 with di-
hydride 16 afforded just a 52.7% of the mixture (24+25+26) and
a high proportion of starting ketones (47.3%). On the other hand,
the reduction in methanol with dihydride 15 led to the mixture
(24+25+26) in quantitative yield containing, as before with ether,
the diastereomer 24 as the main component.
A quick analysis of the results included in Table 2 indicates
that, in the case of the reductions of Mix-22–23 with dihydrides
13–16 carried out without solvent (Table 2, entries 9, 12, 15, 18),
the yields on reduction products were quantitative. The mixtures
obtained contained in all cases the less stable diastereomer 25
(1S, see Scheme 3) in higher proportion. It is indeed remark-
able the dramatic change that occurred in the diastereomers re-
lationship when dihydrides 13–16 were used instead of dihydride
12 for the reduction of (-)-menthone. These results suggest that
the increasing steric volume of the alkyl substituent R at the tin
In summary, the results included in Table
2 indicate that
whereas the reactions of Mix-22–23 carried out with dihydrides
13–16 in absence of solvent (entries 9, 12, 15, 18) gave quantita-
tively mixtures of reduction products (24+25+26), under the same
4

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
Scheme 3. Stereoselective reduction of ketones with diorganotin dihydrides.
reaction conditions the reduction with (-)-MenMeSnH2 (12) (en-
try 3) led to the mixture (24+25+26) in 78.6% yield plus starting
material. These results suggest that the increasing steric volume of
the substituent favors the formation of the less thermodynamically
stable product 25.
Our results are in agreement with many studies on the addi-
tion of organometallic compounds and hydride-reducing agents to
cyclohexanones that show that whereas bulky reagents tend to ap-
proach from the equatorial direction, steric approach control (see
Scheme 3), smaller nucleophiles usually approach from the ax-
ial direction [17,18]. Thus, as shown in Table 2 in the reductions
carried out without solvent, only using the (-)-menthylmethyltin
dihydride (12) (entry 3) could be achieved the preferential ax-
ial attack of the hydrogen that leads to the more thermodynam-
ically stable alcohol 24 (Scheme 3). In compound 24, carbon C-1
has R configuration. On the other hand, dihydrides 13–16 achieve
equatorial hydrogen transfer leading preferentially to alcohol 25
in which the C-1 has the S configuration (Scheme 3). It might
be possible that the reductions with diorganotin dihydrides could
take place via a concerted mechanism of the type depicted in
Scheme 3.
Scheme 4. Reduction of prochiral ketones with chiral dihydrides 12 and 14.
With the aim of determining the degree of asymmetric in-
duction that can be achieved with hydrides 12 and 14, we also
studied the reduction of prochiral acetophenone (27) and 2-
acetylnaphthalene (28) with both hydrides (Scheme 4). In order
to analyze the composition of the resulting mixtures of alcohols,
the crude products were converted into the corresponding mande-
lates. It has been previously reported that the 1H NMR spectrum of
the mixtures of diastereomeric mandelates derived from (R)-(+)-O-
acetylmandelic acid displayed two doublets around 1.50 ppm, and
that whereas the doublet at higher field (1.41 ppm) belonged to
the (R,S) diastereomer, the doublet at lower field (1.54 ppm) corre-
sponded to the (R,R) diastereomer [19,20].
acetates, Fig. 1-i, the doublet at lower field (1.48 ppm) was at-
tributed to diastereomer 36 with configuration (S,S), and the dou-
blet at higher field (1.37 ppm) to diastereomer 35 with configura-
tion (S,R). The GC–MS study showed that the mixture (33 + 34)
gave a chromatogram with two peaks with retention times (rt)
of 20.4 and 20.6 min, and the mixture (35 + 36) gave also two
peaks with rt = 24.8 and 25.1 min. From these results we could
correlate the retentions times with the chemical shifts of the dou-
blets observed in the 1H NMR spectra. Thus, in the case of the es-
ters derived from the reduction of acetophenone (27) the peaks
with rt = 20.4 and 20.6 min could be correlated with the doublet
at 1.46 ppm, i.e., corresponding to the diastereomer (S,S), and the
doublet at 1.33 ppm corresponding to diastereomer (S,R) respec-
tively. Similarly, in the case of 2-acetylnaphthalene (28) the peaks
with rt = 24.8 and 25.1 min could be correlated with the doublets
at 1.48 ppm corresponding to configuration (S,S), and 1.37 ppm to
configuration (S,R) respectively (Fig. 1-iii).
In our case, i.e., the esters derived from (S)-(-)-O-acetylmandelic
acid, the 1H NMR of the mixture (33 + 34), Fig. 1-i also showed
two doublets. We ascribed by analogy, the doublet at lower field
(1.46 ppm) to the configuration (S,S) of ester 34, and the dou-
blet at 1.33 ppm to configuration (S,R) of compound 33. Similarly,
in the case of the mixture of 1-(β-naphthyl)ethylacetoxyphenyl
5

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
(i) Doublets corresponding to phenyl-1-ethyl
racemic mandelates 33 + 34 (Table 5, entry 1).
iii) Chromatogram of the mixture of 2-naphthyl-
1-ethyl mandelates 35 + 36 (Table 5, entry 10).
(ii) Doublets corresponding to the mixture of 2-
naphthyl-1-ethyl mandelates 35 + 36 (Table 5,
entry 10).
Fig. 1. Mixtures of racemic mandelates: expansion of the 1.30–1.55 ppm region (1H NMR), i) 33–34. ii) 35–36. iii) Chromatogram of the mixture 35 + 36.
Table 3
seen in entries 2 (ee = 2) and 5 (ee = 6). When ketones 27
Reduction of acetophenone (21) and 2-acetylnaphthalene (22) with
and 28 were reduced with (-)-Men i-PrSnH2 (14), it was detected
dihydrides 12 and 14.
again that the (S)-enantiomer was formed in higher proportion,
Table 3 entry 3 (ee = 6), and entry 6 (ee = 14).
These results demonstrate that the (-)-menthyl group attached
to the tin atom do exert asymmetric induction, and that the steric
bulk of the (-)-menthylalkyl dihydrides also affects the stereose-
N°
Ar
Hydride
(S,S) (%)
(R,S) (%)
ee (%)
lectivity of these reductions. It is to note, that also the bulk of the
substituents of the ketones has effect on the stereoselectivity of
the reductions. Thus, the reduction of ketone 28 with hydrides 12
and 14 led in both cases to higher ee of the (S) enantiomer than
those obtained in the reduction of acetophenone (27).
1
2
3
pH
LiAlH4
12
50
51
53
50
49
47
0
2
6
pHa
pHb
14
4
5
6
Nph
LiAlH4
12
50
53
57
50
47
43
0
Nphc
Nphd
6
In conclusion, we have obtained five new mixed (-)-
menthylalkyltin dihydrides, (-)-MenRSnH2 (R = Me, i-Pr, n-Bu,
t-Bu, Neophyl), carried out the synthesis of five of their new
precursors, and determined their structures by multinuclear NMR
14
14
Nph = 2-Naphtyl. Retention times (rt):.
a
rt = 20.4 min.
b
rt = 20.6 min.
(
119 Sn, 1H, and 13C) and other physical methods. The new chiral
c
rt = 24.8 min.
d
diorganotin dihydrides show potential as stereoselective reducing
reagents as shown by the study of the reduction of a mixture of
(-)-menthone (95%) and (-)-isomenthone (5%), and of the achiral
acetophenone and 2-acetylnaphthalene. Also, whereas the reduc-
tion of (-)-menthone with LiAlH4, n-Bu2SnH2, and (-)-MenMeSnH2
(12) leads to the more stable (-)-menthol (24) (1R) in higher
proportion, the use of hydrides 13–16 enables to obtain the less
stable (+)-neomenthol 25 (1S) in higher proportion.
rt = 25.1 min.
In summary, the crude mixture of racemic alcohols (29 + 30)
and (31 + 32) was made to react with (S)-(-)-O-acetylmandelic
acid. Then, the stereochemistry of the resulting mixtures of di-
astereomeric mandelates (33 + 34) and (35 + 36) was assessed by
1H NMR analysis [19,20], and quantified by gc-mass spectra. The
mixtures of products resulting from the reduction of ketones 27
and 28 with LiAlH4 were studied following the previous protocol,
and then used as reference in the studies of the reductions with
diorganotin dihydrides 12 and 14. The results obtained in the re-
duction of ketones 27 and 28 are summarized in Table 3.
3. Experimental
3.1. General methods
As shown in Table 3, the reductions proceeded with some de-
gree of stereoselectivity. The reductions of 27 and 28 with (-)-
MenMeSnH2 (12), led in both cases to mixtures in which some
predominance of the (S)-enantiomer was observed. This is clearly
All the solvents and reagents used were analytical reagent
grade. Reactions were monitored by thin-layer chromatography on
silica gel plates (60F-254) visualized under UV light using 5% phos-
phomolybdic acid in ethanol. Column chromatography was per-
6

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
and 1.12 (3JHH 6.6 Hz)]; 1.30–2.04 (m, 15H, from which emerge a
singlet at 1.60 ppm); 7.30–7.41 (m, 1H). 7.43–7.52 (m, 2H); 7.53–
7.62 (m, 2H). 13C NMR (75 MHz, CDCl3): δ = −9.35 (286.3); −9.32
(286.3); 15.78; 22.24; 22.80; 26.71 (58.9); 30.10 (322.3); 32.16
(391.9); 33.12 (30.3); 33.20; 33.32 (32.2); 35.37; 35.71 (6.1); 38.33
(19.9); 40.88 (17.4); 46.60 (15.1); 128.20; 125.38; 125.57; 151.66
(21.5). 119 Sn NMR (CDCl3): δ = −20.6 ppm. MS (EI, 70 eV): m/z
(%) = 407 (3%, [M-CH3]+.); 283 (100%, [M- (C10H19)]+); 139 (2%,
[C10H19]+). Anal. Calc. for C22H38Sn: C, 62.72; H, 9.09. Found: C,
62.68; H, 9.02%
formed over silica gel 60 (70–230 mesh) doped with 10% of potas-
sium fluoride. 1H-, 13C-, and 119 Sn NMR spectra were recorded in
CDCl3, except those of the dihydrides which were run in benzene-
d6, on a Bruker Avance 300 Multinuclear instrument (300.1 MHz
for 1H, 75.5 MHz for 13C and 111.9 MHz for 119 Sn) at 23 °C and
calibrated by using signals from solvents referenced to Me4Si (1H,
13C NMR) and with respect to Me4Sn in the case of 119 Sn NMR
spectra. Chemical shifts (δ) are reported in ppm and coupling con-
stants (J) are in Hz. IR spectra were recorded on a Nicolet Nexus
FT spectrophotometer instrument. Mass spectra (EI, 70 eV) were
obtained using a HP-5890 CG/EM instrument equipped with a se-
lective mass detector and a column INNOWAX, and the quantita-
tive analysis of the mixtures of products obtained in the reductions
was carried out with an Agilent CG-78,903 instrument equipped
with a selective mass detector MS-5977A MSD and a column HP-
5MS (30 m x 0.25 mm x 0.25 m). Specific rotations were measured
with a Polar l-μP, IBZ Messtechnik instrument. Elemental analyses
(C, H) were performed in Exeter Analytical instruments, model CE-
440 at Universidad Nacional del Sur and at UMYMFOR (Universi-
dad de Buenos Aires. Compounds 1–3, 5, 6, and 10 were obtained
following known procedures [7,9,10]. The (S)-(-)-mandelic acid and
(-)-menthone were commercially available.
3.3. Synthesis of (-)-menthylalkyltin dibromides 8, 9, and 11
All the reactions were carried out following the same proce-
dure. One experiment is described in detail in order to illustrate
the methods used. The dibromides could not be purified neither
by fractional distillation nor by column chromatography. So, these
compounds were used without further purification. It is to men-
tion that dibromide 3 has already been reported [9].
3.3.1. Synthesis of (-)-menthyl-n-butyltin dibromide (8)
To a solution of 4 (2.19 g, 6.35 mmol) in methanol (10 mL)
under a nitrogen atmosphere and in the dark, was added drop-
wise and with vigorous stirring a solution of bromine (2.54 g,
15.9 mmol) in methanol (10 mL) at 0 °C. The reaction mix-
ture was stirred for 12 h at room temperature. Then, the solvent
was removed under reduced pressure leading to (-)-menthyln-
butyltin dibromide (8) (3.02 g, 6.36 mmol, 99%) as an orange liq-
3.2. Synthesis of the new (-)-menthyldimethyl alkyltin compounds 4
and 7
All the reactions were carried out following the same proce-
dure. One experiment is described in detail in order to illustrate
the methods used.
uid. [α]20 –24.5 (c. 3.65, benzene). 1H NMR (CDCl3): δ = 0.85 (d,
D
3
3H, JH,H = 6.8 Hz); 0.89–1.18 (m, 11H, from the multiplet emerge
3.2.1. Synthesis of (-)-menthyl-n-butyldimethyltin (4)
three doublets at 0.92 (3JH,H = 5.8 Hz), 0.95 (3JH,H = 7.2 Hz), and
(3JH,H = 6.6 Hz); 1.20–1.56 (m, 5H); 1.59–2.00 (m, 7H); 2.08–2.24
(m, 1H).; 2.26–2.46 (m, 1H). 13C NMR (CDCl3): δ (in ppm) (nJSn,C, in
Hz) = 7.27 (353.6); 15.63; 22.17; 22.72; 26.89 (65.2); 27.35 (58.1);
31.12 (23.7); 31.89 (416.9); 34.04 (21.0); 35.85 (7.3); 35.68 (71.4);
43.13 (18.3); 47.89 (17.1). 119 Sn NMR (CDCl3): δ = 96.23 ppm.
To a stirred solution of (-)-menthyldimethyltin bromide (2)
(4.00 g, 10.9 mmol) in dry diethyl ether (30 mL) under nitrogen,
and at 0 °C, was added dropwise a solution of n-butylmagnesium
bromide (1.6 M, 10 mL, 16 mmol) in dry diethyl ether. The re-
action mixture was further stirred for 12 h at rt. The progress
of the reaction was monitored by TLC and GC–MS. The reaction
was quenched by slow addition of water (6.6 mL) at 0 °C. The
resulting mixture was left under stirring at rt for 1 h. The or-
ganic layer was separated, dried over anhydrous sodium sulfate,
and the solvent was removed under reduced pressure. The crude
product was purified by column chromatography (silica gel 60).
The (-)-Menthyl-n-butyldimethyltin (4) was eluted with hexane
3.3.2. Synthesis of (-)-menthyl i-propyltin dibromide (9)
Following the same procedure, the reaction of (-)-menthyl-
i-propyldimethyltin (5) (1.55 g, 3.68 mmol) with Br2 (2.64
g
(16.5 mmol) in methanol led to (-)-menthyl-i-propyl tin dibromide
(9) (3.05 g, 6.62 mmol, 99%) as an orange liquid. [α]20 –25.7 (c.
D
2.03, benzene). 1H NMR (CDCl3): δ = 0.79 (d, 3H, JH,H = 6.9 Hz);
3
(3.20 g, 9.27 mmol, 85%) as a colorless liquid. [α]20 = –26.6°
D
3
3
(c. 4.71, benzene). 1H NMR (300 MHz, CDCl3): δ = −0.01 (s, 6H,
0.86 (d, 3H, JH,H
=
6.1 Hz); 0.95 (d, 3H, JH,H
=
6.6 Hz);
3
2JSn,H 47.3 Hz,); 0.74 (d, 3H, JH,H
6.8 Hz); 0.77–1.15[m, 13H,
1.00–1.46 (m, superimposed peaks, 10H): two doublets arising
at 1.37 (JH,H 2.5 Hz) and 1.40 (JH,H 2.5 Hz); 2.00–2.40 (m, 3H).
13C NMR (CDCl3): δ = 15.83; 20.46 (15.1); 20.48 (20.1); 21.95;
22.38 (7.2); 26.61 (100.2); 33.71 (371.9); 34.71 (12.6); 35.43 (92.2);
36.29 (34.2); 39.88 (37.3); 46.05 (16.4); 50.42 (361.2). 119 Sn NMR
(CDCl3): δ = 101.5 ppm.
=
superimposed peaks from which clearly emerge three doublets: 0.85
(3JH,H
(3JH,H
6.6 Hz), 0.91 (3JH,H
6.8 Hz)]; 1.16–1.78 (m, 11H); 1.81–1.92 (m, 1H). 13C NMR
7.2 Hz); 0.93 (3JH,H
6.8 Hz), 0.96
=
=
=
=
(75 MHz, CDCl3): δ = −11.49 (283.6); −11.56 (283.6); 10.13 (328.2);
13.91; 15.76; 22.25; 22.79; 26.74 (60.2); 27.46 (55.1); 29.36 (20.7);
31.98 (390.3); 33.54 (19.7); 35.44 (64.3); 35.79 (6.6); 41.13 (17.3);
46.81 (15.0). 119 Sn NMR (CDCl3): δ = 7.7 ppm. . MS (EI, 70 eV):
m/z (%) = 346 (1%, [M]+); 331 (4%, [M-CH3]+); 289 (44%, [M-
(C4H11 )]+); 207 (43%, [M-C10H19 ]+); 151(100%, [Me2SnH]+); 139
(6%, [C10H19 ]+).Anal. Calc. for C16 H34Sn: C, 55.68; H, 9.93. Found:
C, 55.58; H, 9.89%.
3.3.3. Synthesis of (-)-menthylneophyltin dibromide (11)
The reaction of (-)-menthylneophyldimethyltin (7) (2.19 g,
6.61 mmol) with Br2 (1.47 g, 9.20 mmol) in methanol led to (-)-
menthylneophyltin dibromide (11) (2.03 g, 3.68 mmol, 6.62 mmol,
99%)) as an orange oil. [α]20 –22.5 (c. 1.61, benzene). 1H NMR
D
(CDCl3): δ = 0.58–0.95 (m, superimposed peaks, 12H), three dou-
blets emerging at 0.65 (JH,H 6.8 Hz), 0.75 (JH,H 6.6 Hz), and 0.83
(JH,H 6.6 Hz); 1.00–2.00 (m, superimposed peaks, 13H), two sin-
glets emerging at 1.49 and 1.50 ppm; 2.25–2.65 (m, 2H); 7.12–7.23
(m, 1H); 7.25–7.34 (m, 2H); 7.35–7.44 (m, 2H). 13C NMR (CDCl3):
δ = 15.91; 21.74; 22.33 (9.5); 26.63 (111.9): 32.25 (51.2); 32.51
(55.9); 34.47 (13.0); 34.73 (32.0); 35.11; 38.98 (16.7); 39.21 (31.4);
45.75 (23.3); 50.12 (322.9); 50.52 (429.8); 129.22; 125.16; 126.88;
149.81 (35.1). 119 Sn NMR (CDCl3): δ = 49.9 ppm.
3.2.2. Synthesis of (-)-menthylneophyldimethyltin (7)
Following the same procedure, the reaction between (-)-
menthyldimethyltin bromide (2) (5.00 g, 13.6 mmol) and neophyl-
magnesium chloride (0.17 mL, 0.29 mmol, 2.00 M sol. in diethyl
ether), gave compound 7 (2.40 g, 5.70 mmol, 41.9%) as a colorless
oil. [α]20 –25.6° (c. 2.23, benzene). 1H NMR (300 MHz, CDCl3):
D
δ = 0.00 [s, 6H, (2JSnH 46.7 Hz,)]; 0.91 [d, 3H (3JHH 6.6 Hz)]; 0.98–
1.27 (m, 9H, from which emerge two doublets at 1.03 (3JHH 6.6 Hz)
7

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
3
4.6 Hz, JSnH 37.4 Hz). MS (EI, 70 eV): m/z (%) = 316(1%, [M-2]+.);
261(17%, [M- (C4H9)]+); 177 [t-BuSnH]+, 139 (15%, [C10H17 ]+); 119
(64%, [Sn]+), 83(100%, [C6H11 ]+). Anal. Calc. for C14 H30Sn: C, 53.03;
H, 9.53. Found: C, 53.28; H, 9.58%.
3.4. Synthesis of (-)-menthylalkyltin dihydrides 12–16
All the reactions were carried out following the same proce-
dure. One experiment is described in detail in order to illustrate
the methods used. All the manipulations involving the preparation
of the dihydrides were carried out under an argon atmosphere.
3.4.5. Synthesis of (-)-menthylneophyltin dihydride (16)
Following the previous procedure, the reduction of dibromide
11 (1.30 g, 2.36 mmol) with LiAlH4 (0.107 g, 2.83 mmol) led to
(-)-menthyl neophyltin dihydride (16) (0.722 g, 1.83 mmol, 78%)
3.4.1. Synthesis of (-)-menthylmethyltin dihydride (12)
To a solution of LiAlH4 (0.160 g, 4.16 mmol) in dry Et2O (4 mL)
at 0 °C, was added dropwise a solution of 3 (1.50 g, 3.57 mmol)
in dry Et2O (4 mL). Then, the solution was further stirred at rt for
5 h. After cooling, the mixture was decomposed by the addition of
a saturated solution of ammonium chloride (15 mL). The organic
layer was dried over anhydrous sodium sulfate, and the solvent
was removed under reduced pressure. The (-)-Menthylmethyltin
as a colorless liquid. [α]20 –29.8° (c. 6.36, benzene). FT-IR (film):
D
νSn-H = 1826 cm−1
.
1H NMR (C6D6): δ = 0.77 (d, 3H, JHH 6.4 Hz);
3
0.81–1.00 (m, 7H, two doublets emerging at 0.90 (3JH,H 6.1 Hz)
and 0.94 (3JH,H 6.7 Hz); 1.04–1.38 (m, 4H); 1.45 (s, 6H); 1.50–
1
1.58 (m, 5H); 1.59–1.86 (m, 2H); 4.81 (s, 2H, JSnH 1653.9 Hz);
7.05–7.15 (m, 1H); 7.19–7.30 (m, 2H); 7.32–7.41 (m, 2H). MS (EI,
70 eV): m/z (%) = 392 (1%, [M-2]+.); 255 (100%i-propyltin dibro-
mide, [M- (C10H19 )]+); 197 (73%, [C6H6Sn]+); 119 (61%, [Sn]+); 139
(6%, [C10H19 ]+); 91 (96%, [(C7H7)]+); 55(%, [(C4H7)]+). Anal. Calc.
for C20H34Sn: C, 61.09; H, 8.72. Found: C, 61.25; H, 8.82%.
dihydride (12) (0.805 g, 82%) was obtained as a clear liquid. [α]20
D
–32.5° (c, 2.78, benzene). FT-IR (film): νSn-H = 1832 cm−1
.
1H NMR
3
2
(C6D6): δ = 0.14 (t, 3H, JHH 2.7 Hz; JSnH 55.1 Hz); 0.73 (d, 3H,
3JHH 6.9 Hz); 0.78–1.00 [m, 7H; from the multiplet emerge two
doublets at 0.84 (3JHH = 6.1 Hz) and 0.89 (3JHH 6.8 Hz)]; 1.00–
1.48 (m, 4H); 1.50–1.75 (m,2H); 1.76–1.95 (m, 1H); 4.79 (br, 2H,
1JSnH =1677.3 Hz).). MS (EI, 70 eV): m/z (%) = 276(2%, [M-2]+);
261(5%, [M- (CH3)]+); 231(35%,[C8H16 Sn]+), (22%, [C10H19]+); 134
(60%, [CH2Sn]+), 119 (23%, [Sn]+), 83(100%, [C6H11 ]+). Anal. Calc.
for C11 H24Sn: C, 48.04; H, 8.79. Found: C, 48.46; H, 8.92%.
3.5. Reduction of (-)-menthone with (-)-menthylalkyltin dihydrides
12–16
3.5.1. General method
A mixture of (-)-menthone (0.187 g, 1.21 mmol) and dihydride
(1.82 mmol, 1.5 equiv) in an argon atmosphere, was stirred at rt
until the IR spectrum showed that de band corresponding to νC=O
had disappeared. The reaction mixture was diluted with ethanol
(10 ml) for 2hs. The solid was filtered and the solution concen-
trated by removal of the solvent under reduced pressure. The crude
product mixture was analyzed by GC–MS.
3.4.2. Synthesis of (-)-menthyl-n-butyltin dihydride (13)
Following the previous procedure, the reduction of 8 (1.73 g,
3.64 mmol) with LiAlH4 (0.166 g, 4.37 mmol) in ether, led to
(-)-menthyl-n-butyltin dihydride (13) (0.923 g, 2.91 mmol, 76%)
as
a
colorless liquid. [α]20 –29.5° (c. 4.71, benzene). FT-IR
D
(film): νSn-H = 1818 cm−1
.
1H NMR (C6D6): δ = 0.76 (d, 3H,
3JHH = 6.9 Hz); 0.79–1.06 [m, 13H, three doublets emerge at
3.6. Reduction of acetophenone (27) and 2-acetylnaphthalene (28)
using (-)-menthylalkyltin dihydrides 12 and 14, and lialh4. synthesis
of alcohols (29+30) and (31+32)
3
3
0.85 (d, JHH = 6.4 Hz), 0.90 (d, JHH = 7.2 Hz), and 0.91 (d,
3JHH = 6.7 Hz)]; 1.08–1.41 (m, 5H); 1.44–1.80 (m, 6H); 1.84–
1
2.00 (m, 1H); 4.92 (br, 2H, JSnH 1628.6 Hz). MS (EI, 70 eV):
m/z (%) = 346 (1%, [M]+); 331 (4%, [M-CH3]+); 289 (44%, [M-
(C4H11 )]+); 207 (43%, [M-C10H19 ]+); 151(100%, [Me2SnH]+); 139
(6%, [C10H19 ]+). Anal. Calc. for C14 H30Sn: C, 53.03; H, 9.53. Found:
C, 53.33; H, 9.60%.
All the reactions were carried out following the same proce-
dure. One experiment is described in detail in order to illustrate
the methods used.
3.6.1. General method
3.4.3. Synthesis of (-)-menthyl-i-propyltin dihydride (14)
A mixture of acetophenone (0.050 g, 0.42 mmol) and dihydride
(0.62 mmol, 1.5 equiv) was stirred at rt until the νC=O band in
the IR spectrum disappeared (aprox. 3 h), The reaction mixture
was then diluted with ethanol (10 ml) for 2hs. The solid was fil-
tered and the solution concentrated by removal of the solvent un-
der reduced pressure. The crude product mixture was transferred
to a Kugelrohr system, and the distillation under reduced pressure
(150 °C/30 mmHg) gave 1-phenylethanol (0.045 g, 0.37 mmol, 72%)
as a colorless liquid.
Following the previous procedure, the reaction of dibromide 9
(0.600 g, 1.30 mmol) with LiAlH4 (0.059 g, 1.56 mmol) in ether
gave (-)-menthyl-i-propyltin dihydride (14) (0.307 g, 1.01 mmol,
78%) as
a
clear liquid. [α]20 –31.5° (c. 7.73, benzene). FT-IR
D
(film): νSn-H = 1825 cm−1
.
1H NMR (C6D6): δ = 0.51 (d, 3H,
3JHH = 6.5 Hz); 0.55–0.85 [m, 11H, two doublets emerge two
doublets at 0.61 (3JHH = 6.0 Hz), and 0.68 (3JHH = 7.1 Hz)];
0.86–1.60 [m, 13H one doublet emerge at 1.10 (3JHH = 7.1 Hz)];
1
1.61–1.81 (m, 1H); 4.78 [s, 1H, JSnH = 1585.3 Hz)]; 4.83 [s, 1H,
Similarly, the reduction of 2-acetylnaphthalene (0.050 g,
0.29 mmol) with (-)-menthylalkyltin dihydrides (1.5 equiv), after
column chromatography using silica gel 60, led to 1-(naphthalen-
2-yl)ethan-1-ol (0.038 g, 0.22 mmol, 75%) as a white solid, mp 74–
78 °C (Lit. Beilstein, 72–75 °C).
1JSnH = 1582.3 Hz)]. MS (EI, 70 eV): m/z (%) = 302(1%, [M-
2]+.); 261 (17%, [M- (C3H7)]+); 165 (15%, [C10H19 ]+); 137(100%,
[C10H17 ]+); 119(48%, [Sn]+). Anal. Calc. for: C, 51.52; H, 9.31. Found:
C, 51.82; H, 9.27%.
3.4.4. Synthesis of (-)-menthyl-t-butyltin dihydride (15)
3.7. Synthesis of the mixtures of mandelates (33 + 34) and (35+36)
Following the previous procedure, the reaction between t–
butyl(-)-menthyltin dibromide (10) (0.507 g, 1.07 mmol) and
LiAlH4 (0.049 g, 1.28 mmol) in ether gave t–butyl(-)-menthyltin di-
To a solution of 1-phenylethan-1-ol (0.024 g, 0.2 mmol) in
dichloromethane (2 mL), was added 1-dicyclohexylcarbodiimide
(DCC) (0.083 g, 0.4 mmol), (S)-(-)-O-acetyl mandelic acid (0.077 g,
0.4 mmol), and 4-dimethylaminopyridin (DMAP) (0.048 g,
0.04 mmol). After 15 min of stirring at room temperature,
the stirring bar was removed and add an additional 2 ml of
dichloromethane were added. The solution was washed with HCl
10% (1 mL), then a with saturated solution of NaCl (brine, 1 mL), a
hydride (15) (0.400 g, 1.26 mmol, 70%) as a colorless liquid. [α]20
D
.
1H
–23.8° (c. 2.30, benzene). FT-IR (film): νSn-H = 181,815 cm−1
3
NMR (C6D6): δ = 0.77 (d, 3H, JHH 6.4 Hz); 0.82–1.05 (m, 8H, two
doublets emerging at 0.85 (3JH,H 6.4 Hz) and 0.92 (3JH,H 6.7 Hz);
1.07–1.50 (m, 11H, one singlet emerge at 1.29 (3JSnH 69.3 Hz); 1.55–
1
2
1.90 (m, 4H); 1.96–2.10 (m, 2H); 5.27 (d, 2H, JSnH 1550.3 Hz, JHH
8

V.F. Terraza, D.C. Gerbino and J.C. Podestá
Journal of Organometallic Chemistry 935 (2021) 121680
5% NaOH (1,5 mL), and with brine (1.5 mL). The dichloromethane
was dried on anhydrous sodium sulfate, and then filtered and
concentrated at reduced pressure.
[3] (a) A. Davies, Organotin Chemistry, VCH Verlagsgesellschaft, Weinheim, Ger-
many, 2004; (b) P.G. Harrison (Ed.), Chemistry of Tin Blackie and Son, Glasgow,
1999.
[4] (a) T.N. Mitchell, Organotin Reagents in Cross-coupling, Chapter 4, in: Armin
de Meijere, François Diederich (Eds.), Metal-catalyzed Cross-coupling Reac-
tions, Wiley-VCH, Weinheim, 2004 Eds.; (b) “Tin Chemistry, A.G. Davies,
M. Gielen, K.H. Pannell, E.R.T. Tiekink (Eds.), John Wiley & Sons, Chichester,
2008.
The same procedure was used to prepare the mixture of the
mandelates corresponding to 1-(naphthalen-2-yl)ethan-1-ol.
Declaration of Competing Interest
[5] (a) D.C. Gerbino, L.C. Koll, S.D. Mandolesi, J.C. Podestá, Organometallics
27 (2008) 660–665; (b) D.C. Gerbino, J. Scoccia, L.C. Koll, S.D. Mandolesi,
J.C. Podestá, Organometallics (31) (2012) 662–671.
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared to
influence the work reported in this paper.
[6] H.G. Kuivila, O.F.J. Beumel Jr, J. Am. Chem. Soc. 83 (1961) 1246–1250 and ref-
erences therein cited.
[7] H. Schumann, B.C. Wassermann, J. Organomet. Chem. 365 (1989) Cl–C5.
[8] (a) M.H. Abraham, Elsevier, Amsterdam, 1973, p. 70. and references therein
cited; (b) M. Gielen, 1973 Acc. Chem. Res.,
6 198–202; (c) R.K. Ingham,
Acknowledgments
S.D. Rosenmberg, H. Gilman, 1960 Chem. Rev., 60 459–539.
[9] H. Schumann, B.C. Wassermann, J. Pickardt Organometallics 12 (1993)
3051–3063.
[10] H. Schumann, B.C. Wassermann, F.E. Hahn, Organometallics 11 (1992)
2803–2811.
[11] V.F. Terraza, D.C. Gerbino, J.C. Podestá, in: Proceedings of the 19th Int. Electron.
Conf. Synth. Org. Chem., 1–30 November 2015; Sciforum Electronic Conference
Series, 19, 2015, p. a043, doi:10.3390/ecsoc-19- a043.
This work was supported by grants from CONICET, Buenos Aires,
Argentina, PIP project N° 112–201501–00574), and Universidad Na-
cional del Sur (Bahía Blanca, Argentina, PGI 24/Q069). A fellowship
from CIC-PBA to VFT is gratefully acknowledged.
[12] (a) D. Doddrell, I. Burfitt, W. Kitching, C.-.H. Lee, R.J. Mynott, J.L. Consi-
dine, H.G. Kuivila, R.H. Sanna, J. Am. Chem. Soc. 96 (1974) 1640–1642; (b)
T.N. Mitchell, J.C. Podestá, A.D. Ayala, A.B. Chopa, Mag. Reson. Chem. 26 (1988)
497–500.
[13] M.B. Faraoni, V.I. Dodero, L.C. Koll, A.E. Zúñiga, T.N. Mitchell, J.C. Podestá, J.
Organomet. Chem. 691 (2006) 1085–1091.
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.2021.
121680.
[14] J.C. Podestá, A.B. Chopa, G.E. Radivoy, C.A. Vitale, C.A. J., Organomet. Chem. 494
(1995) 11.
[15] S.A. Haut, J. Agric. Food Chem. 33 (1985) 278.
References
[16] Burkhard König, http://www.oc-praktikum.de march 2006.
[17] E.C. Ashby, J.T. Laemmle, J. T., Chem. Rev. 75 (1975) 521–546.
[18] W.G. Dauben, G. Fonken, D.S. Noyce, J. Am. Chem. Soc. 92 (1970) 2579–2582.
[19] I. Chataigner, J. Lebreton, D. Durand, A. Guingant, J. Villiéras, Tetrahedron Lett
39 (1998) 1759–1762.
[1] (a) Á. Raya-Barón, P. Oña-Burgos, I. Fernández, ACS Catal. 9 (2019) 5400–5417;
(b) T. Inagaki, L.T. Phong, A. Furuta, J. Ito, H. Nishiyama, Chem. – A Eur. J. 16
(2010) 3090–3096; (c) Z. Zuo, L. Zhang, X. Leng, Z. Huang Chem. Commun. 51
(2015) 5073–5076.
[20] J.A. Faraldos, J.-.L. Giner, D.H. Smith, M. Wilson, K. Ronhovde, E. Wilson,
D. Clevette, A.E. Holmes, K.J. Rouhier, J. Chem. Ed. 88 (2011) 334–336.
[2] (a) K. Riener, M.P. Högerl, P. Gigler, F.E. Kühn, ACS Catal 2 (2012) 613–621; (b)
T. Imamoto, T. Itoh, Y. Yamanoi, R. Narui, K. Yoshida, Tetrahedron Asymm 17
(2006) 560–565.
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