Carbonyl propargylation and allenylation with 2-propynyl mesylates, tin(IV) iodide, and tetrabutylammonium iodide controlled by either a steric effect or coordination effect

Article abstract of DOI:10.1055/s-2006-944222

A combination of tin(IV) iodide and tetrabutylammonium iodide can be used for propargylation or allenylation of aldehydes with 2-propynyl mesylates in dichloromethane. 1-Methyl-2-propynyl mesylate or 2-butynyl mesylate results in propargylation or allenyl

Full text of DOI:10.1055/s-2006-944222

LETTER
1750
Carbonyl Propargylation and Allenylation with 2-Propynyl Mesylates,
Tin(IV) Iodide, and Tetrabutylammonium Iodide Controlled by Either a
Steric Effect or Coordination Effect
C
arbonyl Propargy
o
lation and
A
s
llenylatio
h
n with
S
nI
a
4 ind TB
A
r
I
o Masuyama,* Ryouichi Yamazuki, Masaru Ohtsuka, Yasuhiko Kurusu
Department of Chemistry, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
Fax +81(3)32383361; E-mail: y-masuya@sophia.ac.jp
Received 22 March 2006
1- or 3-methyl group and the coordination effect of the 3-
Abstract: A combination of tin(IV) iodide and tetrabutylammoni-
trimethylsilyl group.
um iodide can be used for propargylation or allenylation of alde-
hydes with 2-propynyl mesylates in dichloromethane. 1-Methyl-2-
propynyl mesylate or 2-butynyl mesylate results in propargylation
or allenylation controlled by the steric effect of the 1- or 3-methyl
group, and 3-trimethylsilyl-2-propynyl mesylate results in propar-
gylation controlled by the coordination of triiodostannate to silane.
The allenylation and propargylation of benzaldehyde by
2-propynyl mesylate (1a) with tin(IV) iodide and TBAI
were investigated under various conditions. Some repre-
sentative results are summarized in Table 1. Optimal reac-
tion conditions involved the addition of 1a (1.5 mmol) and
benzaldehyde (1 mmol) to a solution of TBAI (3 mmol)
and tin(IV) iodide (1.5 mmol) in dichloromethane (3 mL);
the solution was stirred at room temperature for three
hours; after the usual work-up and purification by column
chromatography and HPLC, a mixture of 1-phenyl-2,3-
butadien-1-ol (2; R1, R2 = H, R3 = Ph) and 1-phenyl-3-bu-
tyn-1-ol (3; R1, R2 = H, R3 = Ph) was obtained in 90%
yield (2/3, 73:27). The reaction of 3-chloro-1-propyne in-
stead of 1a under the conditions described above afforded
a mixture of 2 and 3 in 50% yield (2/3, 72:28). The reac-
tion at 0 °C for 70 hours lowered the yield (82%) of prod-
ucts 2 and 3 without enhancing the selectivity of either the
allenylation or propargylation reaction (Table 1, entry 2).
Dichloromethane is superior to THF as a solvent (Table 1,
entries 1 and 3). Carbonyl allenylations and propargyl-
ations by 2-propynyl mesylates 1a–c were carried out
with various aldehydes under the optimum conditions
(Table 1, entries 4–20). The selectivity between allenyl-
ation and propargylation can be controlled by the bulki-
ness of the 1- or 3-methyl group of 2-propynyl mesylates;
2-butynyl mesylate (1b) causes the allenylation of alde-
hydes, while 1-methyl-2-propynyl mesylate (1c) causes
the propargylation of aldehydes.
Key words: nucleophilic addition, propargylation, allenylation,
tin(IV) iodide, tetrabutylammonium iodide
Since alkynes and allenes are attractive synthetic tools due
to their high reactivities towards metal complexes or
reagents, the preparation of alkynes and allenes is an
important theme.1 Barbier-type carbonyl propargylation
or allenylation with propargylic halides is one of the most
convenient methods for the introduction of propargyl or
allenyl functions.2 The selectivity between propargylation
and allenylation will depend on the equilibrium between
the allenyltin and propargyltin intermediate.2–4 The equi-
librium is usually influenced by the bulkiness of the sub-
stituents (steric effect) and will rarely be determined by
the coordination of the metal moiety to substituents.2k,3f,5
We have found that the selectivity between carbonyl
propargylations and allenylations by 3-halo-1-propynes
or 2-propynyl mesylates with a tin(II) species (trihalostan-
nate), prepared in situ from tin(IV) chloride and tetra-
butylammonium iodide (TBAI) in dichloromethane, is
attributable to the equilibrium controlled by the bulkiness
of the substituents (steric effect),6 which is similar to that
observed with tin(II) halides and tetrabutylammonium ha-
lides in 1,3-dimethylimidazolidin-2-one (DMI).7 The use
of tin(IV) chloride in dichloromethane avoided the trou-
blesome treatment of tin(II) halides after their reaction
with DMI. However, tin(IV) chloride is intractable be-
cause of its instability in water, and furthermore the reduc-
tion of tin(IV) chloride to the tin(II) species needs three
equivalents of TBAI. Thus, we planned (1) the prepara-
tion of a tin(II) species, namely triiodostannate from trac-
table tin(IV) iodide,8 which included a reduction in the
amount of TBAI by two equivalents and (2) the regio-
selective nucleophilic substitution of the triiodostannate
to 2-propynyl mesylates based on the steric effect of the
Both the carbonyl allenylation and propargylation are
outlined in Scheme 1, it is presumed that the carbonyl
allenylation and propargylation are effected by a SnCl4–
TBAI reagent.7 The iodide ion probably serves as a reduc-
–
ing agent for the preparation of triiodostannate ion SnI3
from SnI4 via the formation of pentacoordinate stannate
–
ion SnI5 , followed by the reductive elimination of iodine.
The triiodostannate ion may cause nucleophilic substitu-
tion to propargyl substrates 1 to afford equilibrium mix-
tures of propargyltin and allenyltin intermediates.
Sterically favorable propargyltin (R1 = H, R2 = Me) or
allenyltin (R1 = Me, R2 = H) will function as an active
nucleophile for carbonyl allenylation or propargylation,
respectively. Iodine may react with an equimolar amount
of TBAI to produce tetrabutylammonium triiodide
(TBAI3).
SYNLETT 2006, No. 11, pp 1750–1752
1
2
.0
7
.2
0
0
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Advanced online publication: 04.07.2006
DOI: 10.1055/s-2006-944222; Art ID: U03006ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
Carbonyl Propargylation and Allenylation with SnI4 and TBAI
1751
Table 1 Carbonyl Allenylations and Propargylations with 1a
R1
R2
SnI4 + TBAI
OMs
R3
OH
R2
R1
·
1
R1
SnI4
2
I2
2TBAI
TBAI
Bu4NI3
Bu4NSnI3
– Bu4NOMs
R3CHO
+
+
OMs
R1
CH2Cl2
r.t.
R2
R3
OH
1a: R1, R2 = H
1b: R1 = H, R2 = Me
1c: R1 = Me, R2 = H
R1
R2
R2
SnI3
R1
SnI3
3
R2
·
Entry
1
R3
Time
(h)
Yield 2+3 2/3
(%)b
90
82
74
92
81
89
82
60
31
90
91
76
63
76
55
57
47
47
73
66
(3, syn/anti)c
R1 = H
1) R3CHO
R1 = Me 1) R3CHO
R2 = Me 2) H3O+
R2 = H
2) H3O+
1
2d
3e
4
1a
1a
1a
1a
1a
1a
1a
1a
1a
1b
1b
1b
1b
1b
1c
1c
1c
1c
1c
1c
Ph
Ph
Ph
3
73:27
γ-addition
70
23
3
74:26
R3
R3
55:45
·
OH
OH
4-ClC6H4
4-MeC6H4
PhCH2CH2
Ph(Me)CH
C6H13
67:33
2
3
Scheme 1 A plausible outline for carbonyl allenylation and
5
7
69:31
propargylation
6
18
24
21
17
48
48
48
72
72
48
48
48
64
72
72
62:38
7
67:33
propargylation by 4 with SnI2, TBAI, and NaI in DMI
afforded the same propargylated products as those with
SnI4 and TBAI (Table 2, Method B).7b Thus, on the basis
of the 1H NMR spectral analysis of the reaction of 4 with
SnI2 and NaI in DMF-d7,9 a plausible mechanism is dem-
onstrated as shown in Scheme 2. SnI3– will first attack at
the a-position of the mesyloxy group to prepare
8
66:34
9
c-C6H11
Ph
71:29
10
11
12
13
14
15
16
17
18
19
20
100:0
4-ClC6H4
4-MeC6H4
C6H13
100:0
–
propargyltin intermediate A. Next, excess SnI3 may
100:0
attack the silicon of A to form stannylsilicate B, and then
may slightly migrate from the Si-position to the g-position
to cause a SN2¢ reaction that affords allenyltin intermedi-
ate C.10 The active C will finally cause the usual nucleo-
philic addition at the g-position to aldehydes to produce 5.
No carbonyl allenylation by g-addition of A will occur
owing to the steric hindrance of the bulky trimethylsilyl
group. 3-Triisopropylsilyl-2-propynyl mesylate caused
neither carbonyl propargylation nor allenylation under the
same conditions as those of 4 with SnI4 and TBAI. The
bulkiness of the isopropyl group may disturb the
formation of stannylsilicate, which may induce the
isomerization of 3-triisopropylsilylpropargyltin to 1-tri-
isopropylsilylallenyltin.
100:0
c-C6H11
Ph
100:0
0:100 (54:46)
0:100 (51:49)
0:100 (57:43)
0:100 (33:67)
0:100 (26:74)
0:100 (14:86)
4-ClC6H4
4-MeC6H4
PhCH=CH
C6H13
c-C6H11
a The reactions of 1a–c (1.5 mmol) and aldehydes (1 mmol) with
TBAI (3 mmol) and SnI4 (1.5 mmol) were carried out in CH2Cl2
(3 mL) at r.t.
In conclusion, SnI4–2TBAI is a useful reagent for
Barbier-type carbonyl propargylation and allenylation
without reducing aldehydes. The SnI4–2TBAI reagent can
be applied to propargylation or allenylation based on the
steric effect of the 1- or 3-methyl group and to propargyl-
ation based on the coordination effect of the 3-trimethyl-
silyl group. The SnI4–2TBAI reagent is superior to the
SnI2–TBAI reagent for controlling the selectivity of both
allenylation by 1b and propargylation by 1c, and is also
superior to the SnCl4–3TBAI reagent from the viewpoint
of tractability of tin(IV) halides and resource saving of
TBAI.
b Isolated yields.
c The ratios were determined by 1H NMR analysis (JEOL L-500).
d The reaction was carried out at 0 °C.
e THF (3 mL) was used as the solvent.
3-Trimethylsilyl-2-propynyl mesylate (4) selectively
effected propargylation of aldehydes under the same con-
ditions as those described in Table 1, entry 1 to produce
the corresponding 1-substituted 4-trimethylsilyl-3-butyn-
1-ols 5 (Table 2, Method A). No allenylation was ob-
served with 4; 2-trimethylsilyl-2,3-butadien-1-ols and
their derivatives were not obtained at all. The carbonyl
Synlett 2006, No. 11, 1750–1752 © Thieme Stuttgart · New York

1752
Y. Masuyama et al.
LETTER
Synthesis; Wiley: New York, 1984. (d) Yamamoto, H. In
Table 2 Carbonyl Propargylation with 4
Comprehensive Organic Synthesis, Vol. 2; Trost, M. B.;
Fleming, I., Eds.; Pergamon: Oxford, 1991, 81. (e) Modern
Acetylene Chemistry; Stang, P. J.; Diederich, F., Eds.; VCH:
Weinheim, 1995.
R
RCHO (0.5 mmol)
OMs
Me3Si
4 (0.75 mmol)
solvent (1.5 mL)
r.t.
Me3Si
OH
5
(2) (a) Mukaiyama, T.; Harada, T. Chem. Lett. 1981, 621.
(b) Boldrini, G. P.; Tagliavini, E.; Trombini, C.; Umani-
Ronchi, A. J. Chem. Soc., Chem. Commun. 1986, 685.
(c) Tanaka, H.; Hamatani, T.; Yamashita, S.; Torii, S. Chem.
Lett. 1986, 1461. (d) Iyoda, M.; Kanao, Y.; Nishizaki, M.;
Oda, M. Bull. Chem. Soc. Jpn. 1989, 62, 3380. (e) Belyk,
K.; Rozema, M. J.; Knochel, P. J. Org. Chem. 1992, 57,
4074. (f) Yavari, I.; Riazi-Kermani, F. Synth. Commun.
1995, 25, 2938. (g) Houllemare, D.; Outurquin, F.;
Paulmier, C. J. Chem. Soc., Perkin Trans. 1 1997, 1629.
(h) Bieber, L. W.; da Silva, M. F.; da Costa, R. C.; Silva, L.
O. S. Tetrahedron Lett. 1998, 39, 3655. (i) Kundu, A.;
Prabhakar, S.; Vairamani, M.; Roy, S. Organometallics
1999, 18, 2782. (j) Banerjee, M.; Roy, S. Chem. Commun.
2003, 534. (k) Banerjee, M.; Roy, S. Org. Lett. 2004, 6,
2137.
Entry
R
Method Aa
Method Ba
Time
(h)
Yield 5
Time
(h)
Yield 5
(%)b
(%)b
1
2
3
4
5
6
7
Ph
44
44
45
48
70
72
72
59
44
44
45
48
75
68
72
57
43
51
34
38
44
20
4-ClC6H4
4-MeC6H4
PhCH=CH
PhCH2CH2
C6H13
61
57
49
51
48
c-C6H11
44
(3) For representative non-Barbier-type selective carbonyl
allenylations and propargylations, see: (a) Nokami, J.;
Tamaoka, T.; Koguchi, T.; Okawara, R. Chem. Lett. 1984,
1939. (b) Suzuki, M.; Morita, Y.; Noyori, R. J. Org. Chem.
1990, 55, 441. (c) Brown, H. C.; Khire, U. R.; Narla, G.;
Racherla, U. S. J. Org. Chem. 1995, 60, 544.
a Method A: SnI4 (0.75 mmol), TBAI (1.5 mmol) in CH2Cl2 (1.5 mL)
at r.t. Method B: SnI2 (1.0 mmol), TBAI (0.10 mmol), NaI (1.0 mmol)
in DMI (1.5 mL) at r.t.
b Isolated yields.
(d) Kobayashi, S.; Nishio, K. J. Am. Chem. Soc. 1995, 117,
6392. (e) Marshall, J. A.; Yu, R. H.; Perkins, J. F. J. Org.
Chem. 1995, 60, 5550. (f) Marshall, J. A.; Grant, C. M. J.
Org. Chem. 1999, 64, 8214. (g) Nakajima, M.; Saito, M.;
Hashimoto, S. Tetrahedron: Asymmetry 2002, 13, 2449; and
references cited therein.
OMs
Me3Si
4
–
(4) For the preparation of allenyltin and propargyltin
compounds, see: (a) Guillemin, J.-C.; Malagu, K.
Organometallics 1999, 18, 5259. (b) Kjellgren, J.; Sunden,
H.; Szabo, K. J. J. Am. Chem. Soc. 2005, 127, 1787.
(5) Lin, M. J.; Loh, T. P. J. Am. Chem. Soc. 2003, 125, 13042.
(6) Masuyama, Y.; Watabe, A.; Kurusu, Y. Synlett 2003, 1713.
(7) (a) Masuyama, Y.; Ito, A.; Fukuzawa, M.; Terada, K.;
Kurusu, Y. Chem. Commun. 1998, 2025. (b) Masuyama,
Y.; Watabe, A.; Ito, A.; Kurusu, Y. Chem. Commun. 2000,
2009.
SnI3
–
SnI3
SnI3
SnI3
I3Sn
–
Me Si
Me Me
Me3Si
A
B
–
–
SnI3
I3Sn
(8) For carbonyl allylation with SnI4 and TBAI, see: Masuyama,
Y.; Takeuchi, K.; Kurusu, Y. Tetrahedron Lett. 2005, 46,
2861.
·
Me3Si
C
(9) It was confirmed by 1H NMR analysis (JEOL L-500) that
the reaction of 4 (0.03 mmol) with SnI2 (0.04 mmol) and NaI
(0.04 mmol) in DMF-d7 (0.5 mL) at 25 °C first produced
propargyltin A, d = 4.06 ppm (CH2, s), and then produced a
small yield of allenyltin C, d = 4.90 ppm (C = CH2, s).
(10) (a) Since 1b caused no carbonyl propargylation, 3-
methylpropargyltriiodotin would scarcely isomerize to 1-
methylallenyltriiodotin on account of the steric hindrance of
the methyl group. Thus, the bulkier trimethylsilyl group
should give an unusual effect for the isomerization of A to
C. It is presumed that the formation of a higher coordinated
silicon intermediate causes regioselective ring-opening
reactions of a-silylepoxides at the a-carbon near to the silyl
group: Eisch, J. J.; Galle, J. E. J. Org. Chem. 1976, 41, 2615.
(b) Soderquist, J. A.; Santiago, B. Tetrahedron Lett. 1989,
30, 5693. Following the ring-opening reactions of a-silyl-
epoxides, we propose stannylsilicate B as a plausible
intermediate for the isomerization of A to C.
1) RCHO
2) H3O+
γ-addition
R
Me3Si
OH
5
Scheme 2 A plausible mechanism for the propargylation with 4
References and Notes
(1) (a) Klein, J. In The Chemistry of the Carbon-Carbon Triple
Bond; Patai, S., Ed.; Wiley: New York, 1978, 343.
(b) Moreau, J.-L. In The Chemistry of Ketenes, Allenes, and
Related Compounds; Patai, S., Ed.; Wiley: New York, 1980,
363. (c) Schuster, H. F.; Coppola, G. M. Allenes in Organic
Synlett 2006, No. 11, 1750–1752 © Thieme Stuttgart · New York