Ut. Muellerwesterhoff et M. Zhou, SYNTHESIS OF SYMMETRICALLY AND UNSYMMETRICALLY SUBSTITUTED ALPHA-DIONES FROM ORGANOMETALLIC REAGENTS AND 1,4-DIALKYLPIPERAZINE-2,3-DIONES, Journal of organic chemistry, 59(17), 1994, pp. 4988-4992
The reaction of an equimolar mixture of N,N'-dialkylethylenediamines a
nd diethyl oxalate in diethyl ether or 2-propanol leads to 1,4-dialkyl
piperazine-2,3-diones. As cyclic and nearly planar tetraalkyl oxamides
, these compounds are able to react with 2 equiv of organolithium or G
rignard compounds to form, after hydrolysis, symmetrically substituted
alpha-diones in excellent yields. The sequential addition of 1 equiv
each of two different organolithium compounds affords unsymmetrically
substitute alpha-diones when the more soluble longer chain dialkyl der
ivatives of piperazine-2,3-dione are employed. The dialkylethylenediam
ines can conveniently be recovered and recycled to the 1,4-dialkylpipe
razine-2,3-diones in good yields.