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©Kevin Burgess, March 27, 2017 1
AdditionOfGrignardReagentsToAldehydesAndKetonesfrom chapter(s) _____ in the recommended text
A. Introduction .
©Kevin Burgess, March 27, 2017 2
B. Grignard Reagents: A Type Of Carbanion Equivalents magnesium; strong base cannot be formed from compounds liberating ethyne.
ClMg
Grignard
equivalentto
carbanion
MgCl -
H2O
-HOMgCl
hydrocarbon
Br Mg
Grignard
equivalentto
carbanion
MgBr -
H2O
-HOMgCl
hydrocarbon
©Kevin Burgess, March 27, 2017 3
I Mg
Grignard
equivalentto
carbanion
MgI -
H2O
-HOMgCl
hydrocarbon
Cl Mg
Grignard
equivalentto
carbanion
MgCl -
H2O
-HOMgCl
hydrocarbon
©Kevin Burgess, March 27, 2017 4
1,2-dichloroethane bromobenzene benzyl bromide butane
allyl chloride 2-chloropropane 1,2-diiodopropane 2-chloroethanol
diethyl ether fluoroethane bromoethanal 3-iodopropanol
chloro(methoxy)methane 1-bromo-3-methoxy-ethanal bromoethane
Br Mg
Grignard
equivalentto
carbanion
MgBr -
H2O
-HOMgCl
hydrocarbon
©Kevin Burgess, March 27, 2017 5
C. Reactions Of Methanal With Grignard Reagents
HCOH H H
O O
OH OH+-
GrignardHCOH
OH
GrignardHCOH
OH+-
OH OH
GrignardHCOH
OH+-
GrignardHCOH
OH+-
OH
OH
OH
GrignardHCOH
-
-
OH+
OH+
GrignardHCOH
OH+-
©Kevin Burgess, March 27, 2017 6
primary alcohols one more
MgBr + O+H2O
-HOMgBrOMgBr OH
+ O+H2O
-HOMgBr
MgBrOMgBr OH
O +H2O
-HOMgBr
excess
BrMg MgBr OMgBrBrMgO OHHO
©Kevin Burgess, March 27, 2017 7
primary
O +H2O
-HOMgBrMgBr
OMe OMeOMgBr
OMeOH
O +H2O
-HOMgBrMgBr
OMe OMeOMgBr
OMeOH
OH OHMgBr MgBr
MeO OH HO OH( )3 ( )3
a di-Grignard
MeO MgBr( )3BrMg MgBr( )2
©Kevin Burgess, March 27, 2017 8
more basic than compounds irreversibly. primary because methanal has two secondary alcohols. is unique
Ph OH
a di-Grignard
OH
HO
Ph MgBr
MgBr
MgBr
CD3CH2OH
OMe
OHCD3MgBr
OMe
MgBr
OHOH MgBr
MgBr
OHOHMgBr
MgBr
©Kevin Burgess, March 27, 2017 9
D. Reactions Of Other Aldehydes With Grignards
give secondary alcohols with the same
MeMgBr +O
+H2O
-HOMgBrOMgBr OH
MgBr +O
MeMgBr + EtCOHOH
OH
MgBr + PhCHOPh
OH
©Kevin Burgess, March 27, 2017 10
secondary alcohols
O O
excessMeMgI
OHHO
MgBr OPh+
OHPh
orOH O
+ MeMgBr MgBr +O
OH
MgBr +O
©Kevin Burgess, March 27, 2017 11
OH OHMgBr +BrMg
Oor MeMgBr + OO
Ph
OHMgBr +
O
Ph orO
+ BrMg Ph
OH O
+ BrMg or
O
+MgBr
OH
OH
MgBr + OO
OH
OH+ O
OMeMgBr
©Kevin Burgess, March 27, 2017 12
E. Reactions Of Ketones With Grignards
tertiary alcohols. the same must be the
MeMgCl +O
+H2O
-HOMgClOMgCl OH
MgBr +O HO
MeMgBr + EtCOEtEt Et
HO
OO+ 2PhMgI
HO Ph Ph OH
©Kevin Burgess, March 27, 2017 13
BrMg MgBr2 PhCOMe OH
PhMe
OHPh
Me
O MgBr OH
MeCOEt + PhMgCl Me Et
HOPh
MeCOPh + EtMgBrMe Ph
HOEt
©Kevin Burgess, March 27, 2017 14
is is not possible
HO CD3 or orO
+ CD3MgBr D3C
O+ MeMgBr Me
O
CD3+ EtMgBr
OHor
O
+ MeMgBrO
MgBr
PhHO Ph
Ph
O+ PhMgBr or
Ph
O
Ph + BrMg
HO5 + MeMgBr or + BrMg
O O
©Kevin Burgess, March 27, 2017 15
F. Complimentary Grignard and Hydride Reductions
HO O+ MeMgBr or
O+ BrMg
a Grignard route hydride route
Ph
OH
Ph
O
Ph
O
+ MeMgBr
orO
+ PhMgBr + NaBH4
Ph OH Ph OPh MgBr +H
O
H+ NaBH4
OH OH OH OOH O+ MeMgBr
+ NaBH4
©Kevin Burgess, March 27, 2017 16
HO OO
or
+ MeMgBr
O
+ MgBr
+ NaBH4
OH OO
+ MeMgBr
or
O
+
MgBr+ NaBH4
©Kevin Burgess, March 27, 2017 17
G. Reactions Of Carbon Dioxide With Grignards
carboxylic acid. one more carbon than the Grignard.
MgBr O
O
H2O
-HOMgBr
O
OMgBr
O
OH
MgBr
OMe (i) CO2
(ii) H2O
OMe
O
OH
MgBr (i) CO2
(ii) H2O
COOH
©Kevin Burgess, March 27, 2017 18
(i) CO2
(ii) H2OMgBr COOH
(i) CO2
(ii) H2OBrMg
MgBr
HOOC
COOH
©Kevin Burgess, March 27, 2017 19
almost always
OH
OMgBr
OH
O
HO
OBrMg MgBr
OH
OMgBr
CO2H MgBr
