Organic Reactions Volume 4 - Sciencemadness Dot Org

262 ORGANIC REACTIONS
10-hendecenoate and methyl 9-hendecynoate give the respective
acyloins, l,21-docosadien-ll-one-12~ol and 2,20-docosadiyn~ll-one-12-ol
in 50% yields/ 3 together with 1-2% of the corresponding diketones.
In all the conversions of esters to acyloins, the methyl or ethyl esters
have been used. No data are available concerning esters derived from
alcohols of higher molecular weight. With the exception of the abovementioned
unsaturated esters, the formation of acyloins from esters of
acids containing other functional groups has not been reported. No
mixed acyloins from simultaneous reduction of two different esters are
described. Esters of alicyclic or heterocyclic acids do not appear to
have been studied in this reaction.
Acyloins, when completely free from the yellow diketones, are colorless.
The lower members are liquids, but those that contain sixteen
or more carbon atoms are waxy, white, readily crystallized solids. 12
They are scarcely affected by sodium ethoxide. They form osazones 4 - 6 ' I2
with phenylhydrazine, and monoacetates 12 with acetic anhydride, and
the lower members reduce Fehling's solution. Reduction with hydrogen
and platinum at room temperature or with nickel at 125-150° results
in the formation of glycols. 12 Oxidation with Wijs solution 12 (iodine
monochloride in glacial acetic acid) or with nitric acid 14 has been used
to convert acyloins to the corresponding diketones.
Cyclic Acyloins from Esters of Aliphatic Dibasic Acids. The intramolecular
condensation of esters of dibasic acids, R02C(CH2)nC02R,
in which n is 7 or more, to cyclic acyloins, (CH2) nCHOHCO, was re-
j—. 1
ported 14a in the patent literature in 1941. The reaction was carried out
in xylene using sodium that had been finely dispersed in a colloid mill
More recently this cyclization has been used with remarkable success
by two groups of Swiss investigators uh > c > d to prepare macrocyclic acyloins
containing 9-20 carbons in the cycle. These cyclic acyloins were
obtained in yields of 29-96% without the use of the high dilutions that
have been employed for this Ua and other ue cyclizations of bifunctional
open-chain compounds into large-membered rings, and without using
sodium prepared in a colloid mill; dispersion of the metal by rapid stirring
in hot xylene was quite sufficient.
The success of these cyclizations proved to be primarily dependent
13 Ruzicka, Plattner and Widmer, HeIv. Chim. Acta, 25, 604, 1086 (1942).
14 Fuson, Gray, and Gouza, /. Am. Chem. Soc, 61, 1937 (1939).
Ua Hansley, U. S. pat. 2,228,268 [C. A., 35, 2534 (1941)].
146 Prelog, Frenkiel, Kobelt, and Barman, HeIv. Chim. Acta, 30, 1741 (1947).
14c Stoll and Hulstkamp, HeIv. Chim. Acta, 30, 1815 (1947).
Ud Stoll and Rouve, HeIv. Chim. Acta, 30, 1822 (1947).
14e Ziegler et al., Ann., 504, 94 (1933); 513, 43 (1934); Hunsdiecker, Ber., 75, 1100
(1942).