a,b-不饱和醛酮的还原
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mun1970:213 [5] S.SAITO, H.YAMAMOTO ,.chem. 61:2928(1996)
To state: for the detail of the
mechanism of the reaction is still uncertain ,so we could only offer some
1,4-Reduction
The combined use of ATPH and diisobutylaumium Hydride-n-butyl lithium [5]
Ph
(
O )3 Al O
Ph ATPH
ATPH acts as a
Cover!
Part three
Kinds of the hydride donors
1,2-reduction
NaBH4 in combination with cerium chloride [2]
Dialkylborane 9-BBN [3] Diisobutylalumium hydride [4]
Ce O
BH4
Al OH
DIBAL
In each case ,the reactivity of the carbonyl group is enhanced by a Lewis acid complexed at oxygen
• Both NaBH4 and LiAlH4 have been observed to give both types of product , although the extent of reduction to saturated alcohol is usually greater with NaBH4
23
attention the effect
O
of solution!!
NaBH4 i-PrOH
H O
H A
H
O
H
O
O
+
+
H
HB
HC
Substrates1to 9 refer to page 4
Summery:NaBH4 reduction with i-PrOH
BH4O C C C BH4-
i-PrOH i-PrO-
C C C OB(OR)4- fast i-PrOH
C C C OH + B-(Oi-Pr)4
H O
C C C OB(OR)4- i-PrOH C C C
H
19
OH
+ 19 BH4- C C C
H
H
O
OH
CCC
BH4- C C C
+ 19
O
O
H
20
Summery of part one
Classes of the hydride
• A: LiAlH4 NaBH4 • B: 9－BBN DIBAL
• C: (i-PrO)3Al(see
Meerwein H-
ponndorf W reaction)
t-Bu-MgBr (see
Text10.12)
O
HO
9-BBN
Al H
DIBAL
References:
[1] M. R. Johnson and B.R. Rickborn ,.chem.35:1041(1970) [2] J.-L. Luche ,J.am.chem.soc.,100:2226(1978) [3] K.Krishnamurthy and H.C.Brown ,.chem. 42:1197(1977) [4] K.E.Wilson, R.T.Sejdner and S.masamune ,J.chem.soc.,
experiment data to illustrate it .
! THANKS
O CC C
OH
HO
CC C H
+ HCCC
HH
A
B
Other way to illustrate
O
CH3 O
(CH3)2C CHCCH3 + 2HC C CH2CHCH2
3
21
OH
OH
(CH3)2C CHCHCH2 + (CH3)2CHCH2CHCH2
12
22
+ H2C
CH3 OH C CH2CHCH2
• Solution can lead to other product
See part two to further research
Part two
Several reagents have been developed which lead to exclusive
1,2- or 1,4-reduction
Reduction of a,b unsaturated carbonyl
compounds
Edited by Chen Peng , Gao Dong
Part one
Chemoselective Reductions or not?[1]
By NaBH4 or LiAlH4 A is obtained or B ???
To state: for the detail of the
mechanism of the reaction is still uncertain ,so we could only offer some
1,4-Reduction
The combined use of ATPH and diisobutylaumium Hydride-n-butyl lithium [5]
Ph
(
O )3 Al O
Ph ATPH
ATPH acts as a
Cover!
Part three
Kinds of the hydride donors
1,2-reduction
NaBH4 in combination with cerium chloride [2]
Dialkylborane 9-BBN [3] Diisobutylalumium hydride [4]
Ce O
BH4
Al OH
DIBAL
In each case ,the reactivity of the carbonyl group is enhanced by a Lewis acid complexed at oxygen
• Both NaBH4 and LiAlH4 have been observed to give both types of product , although the extent of reduction to saturated alcohol is usually greater with NaBH4
23
attention the effect
O
of solution!!
NaBH4 i-PrOH
H O
H A
H
O
H
O
O
+
+
H
HB
HC
Substrates1to 9 refer to page 4
Summery:NaBH4 reduction with i-PrOH
BH4O C C C BH4-
i-PrOH i-PrO-
C C C OB(OR)4- fast i-PrOH
C C C OH + B-(Oi-Pr)4
H O
C C C OB(OR)4- i-PrOH C C C
H
19
OH
+ 19 BH4- C C C
H
H
O
OH
CCC
BH4- C C C
+ 19
O
O
H
20
Summery of part one
Classes of the hydride
• A: LiAlH4 NaBH4 • B: 9－BBN DIBAL
• C: (i-PrO)3Al(see
Meerwein H-
ponndorf W reaction)
t-Bu-MgBr (see
Text10.12)
O
HO
9-BBN
Al H
DIBAL
References:
[1] M. R. Johnson and B.R. Rickborn ,.chem.35:1041(1970) [2] J.-L. Luche ,J.am.chem.soc.,100:2226(1978) [3] K.Krishnamurthy and H.C.Brown ,.chem. 42:1197(1977) [4] K.E.Wilson, R.T.Sejdner and S.masamune ,J.chem.soc.,
experiment data to illustrate it .
! THANKS
O CC C
OH
HO
CC C H
+ HCCC
HH
A
B
Other way to illustrate
O
CH3 O
(CH3)2C CHCCH3 + 2HC C CH2CHCH2
3
21
OH
OH
(CH3)2C CHCHCH2 + (CH3)2CHCH2CHCH2
12
22
+ H2C
CH3 OH C CH2CHCH2
• Solution can lead to other product
See part two to further research
Part two
Several reagents have been developed which lead to exclusive
1,2- or 1,4-reduction
Reduction of a,b unsaturated carbonyl
compounds
Edited by Chen Peng , Gao Dong
Part one
Chemoselective Reductions or not?[1]
By NaBH4 or LiAlH4 A is obtained or B ???