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Fulton- Organic
lecture 4
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Cards (7)
NaBH4-
1,4 addition-
-nucleophilic electrons in
B-H
bonds
diffuse
-makes it a
soft
nucleophile
NaBH4/CeCl3-
1,2 addition
CeCl3
is a
lewis acid
it coordinates to the
carbonyl carbon
activating it to
nucleophilic
attack
BH3-
reduction
reagent
-Good reagent for
unreactive
carbonyls
-exists as
gaseous
B2H6
-Can be made into liquid by complexation with Et2O, THF
DIBAL-H
(reduction)
-Structural similarities to LiAlH4 and BH3
-Milder reducing agent than LiAlH4, reduces nitriles to aldehydes
DIBAL-H
most useful reaction
esters
to
aldehydes
-possible because the
tetrahedral
intermediate
formed is
stable
at low temperatures
-followed by higher temp collapsing intermediate and 2nd addition of hydride
Ester
to
aldehyde
difficulty(reduction)
-requires two steps
-aldehydes are more reactive than esters
LiAlH4 followed by PDC
LiBH4
Reduction
-Reduces
esters
to
alcohols
-not as powerful as
LiAlH4-
wont reduce
carboxylic
acids
to
alcohols
-different selectivity to BH3