Organic Reactions Volume 4 - Sciencemadness Dot Org

264 ORGANIC REACTIONS
ACYLOINS FROM ACID CHLORIDES
Acyloins may be obtained by the saponification of the esters of enediols
which result from the reaction of sodium and the acyl chlorides. This
latter reaction is carried out in ether solution. No yields of the diesters
are reported in the earlier work 4 in which butyryl, isobutyryl, and isovaleryl
chlorides were used. Yields of 60-70% of the diesters are reported
from lauroyl, myristoyl, palmitoyl, and stearoyl chlorides. 16
The highly branched trimethylacetyl chloride reacts with sodium to give
hexamethylbiacetyl as the chief product and the monoacyl derivative of
the acyloin as the secondary product. 7
From the data thus far published there appears to be no reason to use
acid chlorides in place of esters for the preparation of acyloins.
ACYLOINS FROM ^-HYDROXY NITRJLES, NICKEL CARBONYL, AND
a-HALO KETONES
A general method for the preparation of both simple and mixed
acyloins involves the reaction of an ^-hydroxy nitrile (from an aldehyde
and hydrogen cyanide) and a Grignard reagent. 16
TlCHOHCN + 2R 7 MgX -» R'H + RCH CR' - ^ RCHOHCOR'
I Il
OMgX NMgX
By this procedure methylpropionylcarbinol, isopropylpropionylcarbinol,
and isobutyroin have been prepared in 60-70% yields/ 6 and
S2/m-diphenylacetoin has been obtained in 45% yield. 17
The preparation of benzoin, butyroin, isobutyroin, and valeroin in
70, 50, 35, and 50% yields respectively from the reaction of nickel
carbonyl with the appropriate Grignard reagent has been reported. 18
The hydrolysis of a-bromo ketones to the corresponding hydroxy
ketones has been used to determine the structure of a variety of brominated
ketones. 19 In this work the acyloins, acetoin and methyltrimethylacetylcarbinol,
as well as a number of dialkylacylcarbinols, R2-
COHCOR', were obtained in 60-75% yields by hydrolysis of the
corresponding bromo ketones in the presence of potassium or barium
15 Ralston and Selby, 'J. Am. Chem. Soc, 61, 1019 (1939).
16 Gauthier, Compt. rend, 152, 1100 (1911).
17 Ruggli and Hegedus, HeIv. Chim. Acta, 25, 1285 (1942).
18 Benton, Voss, and McCusker, J. Am. Chem. Soc, 67, 82 (1945).
19 Faworsky, J. prakt. Chem., [2] 88, 675 (1913).