INTRAMOLECULAR Sm2+ AND Sm3+ PROMOTED REACTION OF γ-OXY-δ-KETOALDEHYDE; STEREOCONTROLLED FORMATION OF PINACOL AND LACTONE

Article abstract of DOI:10.1016/S0040-4039(00)93437-3

Samarium promoted intramolecular pinacol coupling and Tishchenko oxidoreduction of γ-oxy-δ-ketoaldehyde proceeded stereospecifically.Newly forming hydroxy group is oriented anti to γ-silyloxy group in both reactions.

Full text of DOI:10.1016/S0040-4039(00)93437-3

Te~ahedron Letters, Vol.32, No.38, pp 5097-5100, 1991
Printed in Great Britain
0040-4039/91 $3.00 + .00
Pergamon Press plc
INTRAMOLECULAR Sm 2+ AND Sm 3+ PROMOTED R E A C T I O N OF X-OXY-6-KETOALDEHYDE;
STEREOCONTROLLED FORMATION OF PINACOL AND L A C T O N E
Jun'ichi Uenishi, *
Department of Chemistry, O k a y a m a University of Science
R i d a i c h o Okayama, 700 J a p a n
Souichiro Masuda and Shoji Wakabayashi
Summary: S a m a r i u m p r o m o t e d intramolecular p i n a c o l c o u p l i n g and Tishchenko
oxidoreduction of y-oxy-6-ketoaldehyde proceeded stereospecifically.
N e w l y forming h y d r o x y g r o u p is o r i e n t e d anti to T - s i l y o x y g r o u p in both
reactions.
Synthesis of cyclic polyoxo natural product is currently important
task in organic chemistry. I) D u r i n g the course of synthetic studies for
h i g h l y oxidized terpenoids, we n e e d e d to prepare polyols consecutively
e x i s t i n g on five or six m e m b e r e d r i n g . To date t h e r e have been some
s t r a t e g i e s to b u i l d up such f u n c t i o n a l s y s t e m s , e.g. o s m y l a t i o n of
h y d r o x y o l e f i n la) or 1, 4-addition of singlet oxygene. Ib) On the o t h e r
hand,
b e c a u s e it p r o v i d e s
A l t h o u g h number of intramolecular pinacol coupling mediated with low
intramolecular pinacol coupling is attractive for such purpose,
a
new ring and v i c i n a l d i o l s at the same t i m e .
a
v a l e n t metals, particularly SmI2, have been reported, 2) stereochemistry
of face selection to neighbouring substituents has not been elucidated
well. 3)
H e r e i n we wish to r e p o r t stereochemistry of intramolecular pinacol
coupling and Tishchenko oxidoreduction promoted by Sm 2+ and Sm 3+ species
in the case of 7-oxy-~-ketoaldehyde. Treatment of e-benzyloxy-8-dimethyl-
X-(tert-butyldimethylsilyloxy)-6-ketoaldehyde
room temperature gave pinacol in 80 y i e l d as
aldehyde and also afforded the corresponding d i o l s
and 71 yields respectively. Structures of the d i o l s including relative
stereochemistry to a -benzyloxy g r o u p and/or to y - s i l y l o x y g r o u p were
(I) with SmI 2 in THF 4) at
sole product. Keto-
and in 76 %
2
%
a
4
7
5
8
%
confirmed by deriving them to the corresponding 5-membered acetonides. 5)
The results, s h o w n in T a b l e I, c l e a r l y indicated that ci8 vicinal diols
were produced in tran8 form to the adjacent
X-silyloxy group.
formations of 6-1actone were
In some cases of the a b o v e reactions,
o b s e r v e d , but a l w a y s the y i e l d s were f o u n d l a r g e l y d e p e n d e n t on the
5097

5098
T a b l e l
E n t r y
S a m a r i u m Promoted Reactions of 6-Ketoaldehyde
P r o d u c t (yield %)
Substrate
R e a g e n t
Pinacol
Me OBn
6-Lactone
Bn
OBn
M e ~ CHO
.~s,o- -.~o 1
..~Si O" ~'e"OH2 .~siO'~M2~ 3
80
18
0
0
65
89
Smi2 a)
Smi2 b)
Smi2OBut c)
oBn
OBn
OBn
4
. ~ S i 0~'" ~M'~eOH
5
..~"SiO¢'Y
Me
I~
9
Smi2 a)
76
21
0
0
62
75
Smi2 b)
Smi 20But c)
CHO
~L~-"'OH
..~ SiO" "~M'e"OH 8
.
.,,0
--~ si0~° 7
~ 5i0
Me
Me
Smi2 a)
71
35
0
0
41
75
Smi2 b)
Smi 20But c)
CHO
Me°10
~..,,-,,oH
~ ' ~ 1 2
OH11
Me
Me
68
0
i0
ii
SmI 2 a) t
S m I 2 0 Bu
0
--i0 d)
c)
OBn
~Bn
Me"lkI~'"D/Hj._u
Me., /[. /D
Me j~Bn
Me T "C~0
Mo~ -~o
~. siOW'~O
-
-
5i0"
"',,
q ' ' O H
2
~
O
~
°
'
Me
1
-s,. Mie..~
3
Me
~
D
67
20
12
13
Smi2 e)
Smi2 e)
OBn
Me.
#OBn
Sn
Me, JL. /D
Me
0
Me--ix/ "C~O
4'
6'
Me
" ~
Me' D
16
62
(a)THF, r.t. One eq. of SmI 2 p r e p a r e d freshly in THF (0.1 M) was used
(b)THF:hexane (i:i), r.t. T~F solution of SmI 2 (0.i M) was premixed
with m e t h a n o l in
a r a t i o of 99:1 b e f o r e the addition. (c)THF, r.t.
(d)This reaction was m e s s y and a l d o l products were isolated.
(e)Older SmI 2 was used.

•
5099
quality of the reagent. 6) The lactones were resulted by intramolecular
Tishchenko oxidoreduction 7) between aldehYdes and methyl ketones. These
results imply that Sm 3+ species,
presumably present in SmI 2 reagent,
instead
m i g h t mediate the reaction. In fact when SmI2OBut8) was employed
of SmI2, lactones ware produced exclusively and none of the pinacol was
obtained (entries 3, and 9). Addition of small amount of methanol also
promoted lactone formation (entries 2, and 8) in w h i c h SmI2OMe m i g h t be
formed in 8itu from methanol and Sm 3+ species. In this reaction, somehow
y-silyloxy g r o u p is required essentially. Although the reason is not
clear at present, simple 6-ketoaldehyde 10 provided lactone 12 very
6
5
a
poorly even by the use of SmI2OBut (entry 11). However it gave pinacol 11
by the reaction with SmI 2 in good yield (entry 10).
The obtained lactones
3
and
6
were consisted of
a single stereoisomer
and the structures were shown in T a b l e I.
The stereochemistry of the
n e w l y produced secondary hydroxy center was found to be anti in relation
to the a j a c e n t s i l y l o x y g r o u p a l o n g the z i g - z a g c a r b o n c h a i n in all
c a s e s . The s t e r e o c h e m i s t r y was d e t e r m i n e d by t r a n s f o r m a t i o n of the
lactones
3
and
6
to tran8 epoxides (both, J=2.2 Hz) respectively by
3
steps conversion (cis epoxides both, J = 4 . 4 Hz). 9)
A
source of proton used
in r e d u c t i o n was f o u n d to come from a l d e h y d e by an e x p e r i m e n t u s i n g
deuterated aldehyde in w h i c h the produced lactone possessed quantitative
incorporation of deuterium in the NMR spectrum (entries 12
and 13).
The reaction mechanism c o u l d be explained as follow (shown in the next
s c h e m e ) .
A d d i t i o n of Sm 3+ (e.g. S m I 2 O B u t ) to a l d e h y d e f o l l o w e d by
cordination with methyl ketone formed cyclic intermediate. Then hydrogen
s h i f t e d to the k e t o n e ,
e l i m i n a t i o n
p o s s i b l e configurations, such as the form
may undergo through the form and non-chelation type of face selection
to Y - s i l y l o x y methyl ketone (in F i g . ) was postulated by considering the
s t e r e o c h e m i c a l a n a l y s i s of the p r o d u c t . Same s t e r e o c h e m i c a l face
and s u c c e s s i v e l y l a c t o n e was
of S m I 2 O B u t . I n t e r m e d i a r y s a m a r i u m c o m p l e x may take two
and the form II. The reaction
f o r m e d a f t e r
I
I
selection was observed in the former pinacol coupling process (in the
Fig.).
F
Mo
0But
F i g u r e
Tishchenko Reaction
c
eme
Sm/2OBut
~ 0
,,,, /-
Ox@,,,O
s i ° / ~ [ ' °
9
0
Me
H~
s
M~
O\
~
, R (\
7
SmI 2OBut~
I/5~Im
|
1/5~?
1x / I
5m
Ix /I
Sm
smI2oBut
n
,0
~ "s i O ~6
o
S ~
"
",
( 3
"~
,
Me
H
~ ~ OSu~
x"
Me
Pinacol Coupling
II

5100
In conclusion in both the pinacol coupling and the lactone formation
recation, hydroxy g r o u p forming at the new stereogenic center orients
anti to the silyloxy g r o u p in both cases. The novel lactone formation
a
reported here is the first intramolecular Tishchenko oxidoreduction and
is perfectly stereocontrolled. These results will be useful for polyoxo
natural product synthesis.
Aknowledgement: A u t h o r s are appreciate to Prof. J. Inanaga for v a l u a b l e
discussions and technical advice.
References and N o t e s
i, For example; F o r s k o l i n syntheses, a)S.Hashimoto, S.Sakata,
M . S o n e g a w a and S.Ikegami, J.Am.Chem. Soc., ii0, 3670 (1988).
b)E.J.Corey, P.D.S.Jardine and J.C.Rohloff, ibid., ii0, 3672 (1988).
2, G.A.Molander and C.Kenny, J.Am.Chem. Soc., iii, 8236 (1989) and
references c i t e d therein.
3, J.L.Chiana, W . C a b r i and S.Hanessian, Tetrahedron Lett., 32, 1125
(1991).
4, T.Inamoto and M.Ono, Chem.Lett., 501 (1986).
5, The pinacols
2 and 5 were transformed to acetonide monoacetate
respectively, s h o w n in the following scheme.
~
OAc
i
~
~ 0
I)Pd/C, H 2
2) Me2C (OMe) 2,
+
~
l)Pd/C, H 2
2) Me2C (OMe) 2' H+
H
•
3-..0
-
2
~
Me
J
3)Ac20,pyridine ~S,0
~
OAc
3) Ac20, p y r i d i n e ~ ~ siO~'~l'~.,,O ~
5
6, When o l d e r SmI 2, p r e s u m a b l y containing some Sm 3+ species by the
r e s u l t of air oxidation, was used,
a r a t i o of lactone/diol was
increased.
7, R e c e n t intermolecular Tishchenko oxidoreduction, see D.A.Evans and
A.H.Haveyda, J.Am. Chem. Soc., 112, 6447 (1990).
8, J.Collin, J . - N . N a m y and H.Kagan, Nouv.J.Chem., 10, 229 (1986).
9, Transformations of the 6-1actones
3 and 6 to tran8 epoxyesters and
synthesis of o t h e r possible stereoisomeric 6-1actones and ci8
epoxyesters are d e s c r i b e d below.
OBn
i0) a,b
o
d,e,f
~.,,,n c ~
OBn
/
~
I
~
3
~
" H ~ H J=2.2 HZ
~
s
s%
o ~ O~°o e, ~, f _~cooM~~....y
SiO"
T
~
Me
~
Me
~
J=4.4 Hz
OSn
OBn 10)
oBn
Ne
OBn
~ H ~ N e H I
~
OEt
~
H
J = 2 . 2 Hz
J = 4 . 4 Hz
a ) C F 3 C O O H, b)NCS,AgNO3, a)SmI2OBut , d)Bun4NF, e)MsOl,pyridine,
f)K2CO3,MeOH , g)DIBAL, h)Jones O x i d a t i o n
i0, J.uenishi, Y . K a w a c h i and S.Wakabayashi, J.Chem. Soc., Chem.Commun.,
1033 (1990).
(Received in Japan 10 June 1991)