Handbook of Functionalized Organometallics Applications in S

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13 Manganese Organometallics for the Chemoselective Synthesis of Polyfunctional Compounds
13.3
1,2-Addition to Aldehydes and Ketones
13.3.1
Chemoselective 1,2-Addition of Organomanganese Reagents to Carbonyl
Compounds
In ether, organomanganese halides readily add to aldehydes and ketones at 0 C,
affording the corresponding alcohols in high yields. However, they react neither
with nitriles nor with less reactive carbonyl compounds such as amides and
esters, except with formates [11] (Scheme 13.5).
BuMnBr +
BuMnBr +
Scheme 13.5
O
CO 2Et
Et 2O
20ºC
Bu
OH
NC CHO Et2O NC
20ºC
91%
Bu
95%
OH
CO 2Et
Contrary to organolithium or organomagnesium compounds, organomanganese
halides add chemoselectively to aldehydes in the presence of ketones
(Scheme 13.6) [12]. The scope of the reaction is very large since n- or s-alkyl, alkenyl,
aryl and alkynylmanganese halides are always completely aldehyde-selective
at room temperature, in ether as in THF.
RMnBr
HexCHO + PrCOPr HexCHOHR + PrCOPr
Et2O Scheme 13.6
R Yield (%)*
Bu 93
Ph 94
Me2C=CH 98
Bu C C
80
* PrCOPr is quantitatively recovered
On the other hand, aliphatic (n-, s- or t-alkyl), ethylenic and aromatic aldehydes
have been selectively converted in high yields into the corresponding secondary
alcohols in the presence of aliphatic, ethylenic or aromatic ketones.