Either g-syn- or g-anti-selective palladium-catalysed carbonyl allylation by
mixed (E)- and (Z)-1,3-dichloropropene with tin(ii) halides
Yoshiro Masuyama,* Akihiro Ito and Yasuhiko Kurusu
Department of Chemistry, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102, Japan
Table 1 Allylation of benzaldehyde by 1,3-dichloropropene (1)
Palladium-catalysed carbonyl allylations by mixed (E)- and
(Z)-1,3-dichloropropene with SnI2–Bu4NI and SnCl2 dia-
Yielda of 2
stereoselectively produce syn and anti 1-substituted
(R = Ph)
(%)
2-chlorobut-3-en-1-ols, respectively. These are transformed
X
XA
t/h
24
65
130
125
121
122
70
2s:2ab
into cis and trans 1-substituted 2-vinyl epoxides.
Clc
Cle
Br
Br
I
88
70
22
87
66
63
65
65
41:59
22:78
46:54
85:15
90:10
92:8
d
d
Barbier-type carbonyl allylations by (E)-g-substituted allylic
metal reagents, derived from (E)-g-substituted allylic halides
with metals or metal halides, usually add anti-diastereoselec-
tively at the g-position of the allylic metal reagents to
aldehydes; g-anti-selective carbonyl allylation.1 g-syn-Selec-
tion is difficult for the Barbier-type carbonyl allylations by
(E)-g-substituted allylic metal reagents. We have found that
halogens on the tin of but-2-enyltin reagents, prepared from
(E)-rich 1-bromobut-2-ene and tin(ii) halides, affect the dia-
stereoselectivity in the g-regioselective carbonyl allylation in
THF–H2O at room temperature; anti-selection with tin(ii)
chloride and syn-selection with tin(ii) iodide–tetrabutylammo-
nium bromide (or iodide).2 We thus hoped that palladium-
catalysed carbonyl allylation3 by (E)-rich 3-chloroprop-2-
enyltin reagents, derived from (E)- and (Z)-mixed 1,3-dichlo-
ropropene (1)† with SnCl2 or SnI2–Bu4NI via the formation of
1-chloro-syn-p-allylpalladium complex, could lead to halogen-
coordination controlled diastereoselectivity to produce dias-
tereo-defined 1-substituted 2-chlorobut-3-en-1-ols, which could
be transformed into the corresponding 1-substituted 2-vinyl
epoxides (Scheme 1).5
Br
I
Br
I
I
If
I
Ic
91:9
92:8
Ic
71
a
b
Isolated yields. The ratio was determined by 1H NMR spectroscopy
c
d
(JEOL GX-270).§ PdCl2(PhCN)2 as a catalyst was added. No TBAXA
was used. e The reaction was carried out without H2O at 0 °C. f TBAI (0.2
mmol) and NaI (2.0 mmol) were used.
PdCl2(PhCN)2 accelerated the carbonyl allylation with SnI2 and
TBAI without lowering the syn-selectivity. The reaction with
NaI accompanied by a catalytic amount of TBAI exhibited the
same reactivity and selectivity as those of the reaction with an
equimolar amount of TBAI to 1.
Either syn- or anti-selective palladium-catalysed allylations
of various aldehydes by 1 were carried out with SnI2–TBAI–
Table 2 Diastereoselective carbonyl allylation by 1a
Diastereoselectivity in the allylation of benzaldehyde by (E)-
and (Z)-mixed 1,3-dichloropropene (1) in 1,3-dimethyl-
imidazolidin-2-one (DMI)–H2O‡ was investigated with tin(ii)
halides (SnX2) and tetrabutylammonium halides (TBAXA). To a
solution of SnX2 (2.0 mmol) and TBAXA (2.0 mmol) in DMI (3
ml)–H2O (0.1 ml) in the presence or absence of a catalytic
amount of PdCl2(PhCN)2 (0.02 mmol) was added 1 (2.0 mmol),
and the solution was stirred at room temperature for 24 h.
Benzaldehyde (1.0 mmol) was added to the solution, which was
then stirred at room temperature. After the usual work-up,
2-chloro-1-phenylbut-3-en-1-ol (2, RNPh) was obtained. The
results are summarized in Table 1. The palladium-catalysed
carbonyl allylation with SnCl2 in DMI without H2O led to usual
anti-selectivity.3 For addition of TBAXA, the carbonyl allylation
with SnBr2 or SnI2 proceeded without any palladium catalyst.
Use of either iodide (SnI2 or TBAI) enhanced both the yield and
A: (1) Pd/SnCl2, DMI,
OH
OH
room temp., 24 h
(2) RCHO, 0 °C
R
Cl
Cl
+
R
Cl
Cl
B: (1) Pd/SnI2, DMI–H2O,
room temp., 24 h
1
2s, syn
2a, anti
(2) TBA–Nal, room temp., 3 h
(3) RCHO
Yieldb of 2
R
Method
t/h
(%)
2s:2ac
4-ClC6H4
4-ClC6H4
4-NCC6H4
4-NCC6H4
4-H3CC6H4
4-H3CC6H4
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
70
71
71
68
62
72
78
97
72
96
71
96
93
95
70
94
74
80
71
72
58
49
56
24
78
53
58
64
48
48
62
63
14:86
93:7
15:85
91:9
20:80
91:9
24:76
93:7
15:85a
77:23d
32:68
76:24
36:64
84:16
26:74
78:22
the syn-selectivity. Addition of
a
catalytic amount of
3,4-(CH2O2)C6H3
3,4-(CH2O2)C6H3
(E)-C6H5CHNCH
(E)-C6H5CHNCH
C6H5CH2CH2
C6H5CH2CH2
CH3(CH2)5
OH
R
R
O
SnCl2
Cl
2a, anti
3t, trans
Cl
Cl
CH3(CH2)5
RCHO
base
CH2NCH(CH2)8
CH2NCH(CH2)8
1
OH
Snl2
TBAl
R
a The allylation of aldehydes (1.0 mmol) by 1 (2.0 mmol) was carried out
R
O
with PdCl2(PhCN)2 (0.02 mmol), SnX2 (2.0 mmol), TBAI (0.2 mmol) and
Cl
2s, syn
b
c
NaI (2.0 mmol) in DMI (3 ml) and H2O (0.1 ml). Isolated yields. The
3c, cis
ratio was determined by 1H NMR spectroscopy (JEOL GX-270).§ The
d
Scheme 1
ratios (cis:trans) refer to the corresponding vinyl epoxides.
Chem. Commun., 1998
315