Reaction of allylic-type diindium compounds with electrophiles

Article abstract of DOI:10.1246/cl.2006.314

Allylic-type diindium reagents were prepared from 3-bromo-1-iodopropene (1a), 3-bromo-1-iodo-1-phenylpropene (1b), or 2,4-diiodobut-2-en-1-ol (1c) with metallic indium, and their successive coupling with electrophiles was examined. The coupling behavior o

Full text of DOI:10.1246/cl.2006.314

314
Chemistry Letters Vol.35, No.3 (2006)
Reaction of Allylic-type Diindium Compounds with Electrophiles
Tsunehisa Hirashita,Ã Shun Arai, Kazuma Mitsui, Hajime Makino, and Shuki Araki
Omohi College, Graduate School of Engineering, Nagoya Institute of Technology,
Gokiso-cho, Showa-ku, Nagoya 466-8555
(Received January 5, 2006; CL-060009; E-mail: hirasita@nitech.ac.jp)
Allylic-type diindium reagents were prepared from 3-
In order to estimate the difference in reactivity between diin-
diopropene Ia (I0a) and allylindium sesquiiodide (III) toward
electrophiles, competitive reactions were performed by using
benzaldehyde (5a), sulfonimine 5b, and acetophenone (5c) as
electrophiles (Table 1). It was found that the chemoselectivity
of Ia (I0a) is higher than that of III. In the competitive reaction
of 5a and 5b, allylindium III gave a mixture of 2a and 2b,
whereas 2a was selectively obtained with diindium Ia (I0a) (En-
try 1, Table 1). The results of 5b/5c indicate that diindiopropene
Ia (I0a) reacts with 5b approximately seven times faster than 5c,
but only twice as fast in the case of III (Entries 2 and 3).
Next, a diastereoselective allylation of imines 5d derived
from (S)-valine with Ia (I0a) and III was examined (Table 2).
The reaction with 1a afforded the allylated product with much
higher selectivity (Table 2, Entry 1) than that with III (Entry
2). This reaction behavior of diindiopropene Ia (I0a) opens up
a possibility for higher chemo- and stereoselective allylation
than that with conventional allylindium reagent (III). Presuma-
bly, the difference between I and III may be explained by the
Lewis acidity and/or the bulkiness arising from the two indium
atoms on the diindiopropene.
bromo-1-iodopropene (1a), 3-bromo-1-iodo-1-phenylpropene
(1b), or 2,4-diiodobut-2-en-1-ol (1c) with metallic indium, and
their successive coupling with electrophiles was examined.
The coupling behavior of the diindium reagents was found to de-
pend on the electrophiles and the substituent on the diindium
compounds.
Organodimetallic compounds, which contain two metal–
carbon bonds in one molecule, are attractive molecules from
the standpoint of synthetic reagents.1 We have reported that
the oxidative addition of indium to 3-bromo-1-iodopropene
(1a) generates diindiopropene Ia (I0a). This compound couples
with carbonyl compounds and imines, and the resulting vinylin-
dium compounds react further with aryl, alkenyl, or allyl halide
in the presence of Pd(PPh3)4 to give linear homoallylic alcohols
or amines.2 The reaction courses of allylic-type diindium
reagents with two electrophiles can be classified into three types,
A–C (Scheme 1). We previously showed that the reaction of Ia
(I0a) proceeds via type A course leading to 2.2
Table 1. Chemoselectivity of Ia (I0a) and III toward electro-
R
philesa
3
In
1
X1
X2
2
Ia (I'a)
Y
1a: R = H, X1= I, X2= Br, 1b: R = Ph, X1= I, X2= Br,
1c: R = CH2OH, X1= X2= I
Y
or
I
+
H
THF
R
Ph
Ph
R
I
In
In
5a: R = H, Y = O
5b: R = H, Y = NSO2Ph
5c: R = Me, Y = O
2a-c
R
R
I
L2In
L2In
3
1
III
3
1
L2In
InL2
2
2
Ratio of Products/%b
Ia-c
I'a-c
Diindiopropene Ia (I0a) Allylindium sesquiiodide (III)
Entry Solvent
E1
R
Attack at C1
Attack at C3
2a
2b
2c
2a
2b
2c
1
2
3
THF
THF
DMA
100
—
0
87
87
—
13
13
63
—
—
37
63
68
—
37
32
R
InL2
L2In
R
—
L2In
E1
1
1
E1
E1
aAll reactions were carried out with a half amount of the allylating agent
to a 1:1 mixture of two electropliles (each 0.5 mmol) at room temperature
for 17 h. bThe ratio was determined on the basis of 1H NMR analysis of a
mixture of two products.
3
3
2
2
II'a-c
IIa-c
Attack at C1
E2
E2
Attack at C3
Table 2. Diastereoselective allylation of 5d derived from (S)-
valine
Type A
Type B
Type C
R
R
R
E1
E2
E1
E2
E2
E1
Ia (I'a)
or
+
2
3
4
THF
Ph
N
5d
CO2Me
Ph
N
H
CO2Me
SS:RS
III
Type
nucleophilic attack
product
first
second
Entry
Allylindium
Ia (I0a)
III
Conditions
Yield/%
1a
2b
rt, 44 h
rt, 36 h
54
100
98:2
75:25
C3
C1
C1
C1
C1
C3
A
B
C
2
3
4
aThe reaction was carried out with In (1.5 mmol), 1a (0.75 mmol),
and 5d (0.50 mmol). bFrom Ref. 3.
Scheme 1. Reaction course of allylic-type diindium.
Copyright Ó 2006 The Chemical Society of Japan

Chemistry Letters Vol.35, No.3 (2006)
315
Table 3. In-mediated reaction of 1b with aldehydes and iminea
Ph
L2In
O
H+
H
Ph
H+
H
Ph
N
Type A
Type C
Y
In
Ph
Ph
+
1b
PhO2S
DMI
R
H
Ph
R
OH
+
+
R
R
+
InL2
InL2
L2In
OH
OH
2
4
5e: R = H, Y = O
5f: R = Et, Y = O
5g: R = n-C6H13, Y = O
5h: R =c-C6H11, Y = O
5i: R = Me2CH, Y = O
Figure 1.
Table 4. In-mediated reaction of 1c with benzaldehydea
Ph
Type B
Ph
R
HO
R
R
OH
YH
30 (%)
3
3'
Type A
OH
Type B
HO
Ph
OH
Entry
5 (mol %)
2 (%)
3 (%)
4 (%)
OH
In
30e: 23
30f: 5b
30g: 9b
30h: 18e
30i: 42b
30a: 77e
30b: 90g
0
PhCHO
1c
1
2
3
4
5
6
7
5e (200)
5f (200)
5g (200)
5h (200)
5i (50)
0
3e: 77
3f: 15b
+
+
Ph
0
4f: 30c
2'h
3'h
6
H(D)
OH
4g: 30b
Ph
0
0
0
0
0
0
2h: 36d
0
0
0
0
Yield/%
20h (E:Z)
72 (30:70)
20 (80:20)
45 (50:50) (D 64%)c
2i: 44f
Entry
Solvent
30h
6
10b
45b
trace
5a (50)
5b (50)
0
0
1
2
3
DMI
THF–H2O (1:1)
THF
15
15
22
aAll reactions were carried out with In (1.0 mmol), 1b (0.50 mmol), and 5
in DMI (1,3-dimethyl-2-imidazolidinone, 1.5 mL) at room temperature
for 4 h. bDiastereomeric ratio was not determined. cTwo diastereomers
(9:1) were found by 1H and 13C NMR. dE:Z = 40:60. eSyn:anti =
<1:>99. fE:Z = 33:67. gSyn:anti = >99:<1.
aAll reactions were carried out with In (1.0 mmol), 1c (0.50 mmol), and
PhCHO (0.25 mmol) in solvent (1.0 mL) at room temperature for 2 h.
bE:Z ratio was not determined. cQuenched by 1 M DCl.
To disclose further the reaction behavior of diindiopropene,
new allylic-type diindium reagents bearing a phenyl (1b) or a hy-
droxymethyl group (1c) on the C1 position were prepared. Prior
to the reaction of 1b with aldehydes, the existence of diindium Ib
(I0b) was confirmed by the following reaction: A mixture of 1b
(0.50 mmol) and indium (1.0 mmol) in THF was stirred for 2 h.
The reaction mixture was quenched with 1 M hydrochloric acid
and the product was extracted with ether. The product was ana-
lyzed by GC, showing that allylbenzene was formed in 60%
yield. This fact clearly indicates the formation of the diindium
reagent Ib (I0b) and the protonolysis of Ib (I0b) proceeds via
type B course.
A) was obtained as a main product together with diol 30h (type
B) and diene 6 (Entry 1, Table 4). In an aqueous medium, the
yield of 6 was increased (Entry 2), whereas in THF 20h was
obtained in 45% yield and 6 was scarcely observed (Entry 3).
Diene 6 may come from the C1 attack of benzaldehyde, followed
by the elimination of InOInL2 from II0c prior to protonolysis.
In summary, the reaction behavior of the allylic-type diindi-
um reagents toward electrophiles was found to differ considera-
bly depending on both the electrophiles and the substituent on
the diindiopropene. The coupling of Ib (I0b) proceeded via type
B with small electrophiles, such as proton and formaldehyde,
whereas the reaction course turned to type A and C with increas-
ing the bulkiness of electrophiles. The diindiopropene Ic (I0c)
bearing a hydroxymethyl group was prone to react with benzal-
dehyde via type A leading to the corresponding linear diol.
Next, the diindium reagent Ib (I0b) was subjected to the re-
action of aldehydes and it is found that the reaction courses are
distinct depending on aldehydes (Table 3).
With formaldehyde (5e), diol 3e was obtained in 77% yield
together with 30e in 23% yield (Entry 1, Table 3). Propionalde-
hyde (5f) gave a regioisomer mixture of 3f and 4f along with a
small amount of 30f (Entry 2). Hexanal (5g) gave diol 4g and ho-
moallylic alcohol 30g (Entry 3), whereas bulky aldehydes 5h and
5i gave no diol product but yielded homoallylic alcohols 2 and 30
(Entries 4 and 5). With benzaldehyde (5a), homoallylic alcohol
30a was solely obtained in high yield with anti-selectivity (Entry
6), whereas sulfonimine 5b gave 30b with syn-selectivity (Entry
7). As allylic indium compounds are known to be protonated at
the ꢀ-position, the anti- and syn-stereochemistry of 30a and 30b
can be rationalized by the attack of the proton toward the result-
ing allylic indium compounds IIb from the less hindered direc-
tion with regio- and stereoselectivity (Figure 1).4
This work was partially supported by a Grant-in-Aid for Sci-
entific Research (No. 14340195) from the Ministry of Education,
Culture, Sports, Science and Technology, Japan.
References
1
a) I. Marek, L.-F. Normant, Chem. Rev. 1996, 96, 3241.
b) E. M. Flamme, W. R. Roush, J. Am. Chem. Soc. 2002,
124, 13644.
2
a) T. Hirashita, H. Yamamura, M. Kawai, S. Araki, Chem.
Commun. 2001, 387. b) T. Hirashita, Y. Hayashi, K. Mitsui,
S. Araki, J. Org. Chem. 2003, 68, 1309.
3
4
T. Basile, A. Bocoum, D. Savoia, A. Umani-Ronchi, J. Org.
Chem. 1994, 59, 7766.
M. N. Paddon-Row, N. G. Rondan, K. N. Houk, J. Am.
Chem. Soc. 1982, 104, 7162.
Finally, the reaction of 1c with benzaldehyde was studied
and the results are shown in Table 4. In DMI, diol 20h (type
Published on the web (Advance View) March 5, 2006; DOI 10.1246/cl.2006.314