Addition to Carbon-Carbon Double Bonds(XLII)Me.Cx5
\CH COjEt
EOEI |
CH,(CO,Et), > CO,Et
(XLIII)CH,O^0
/
CH=C
/ \
Me,C CH,
\
CHCO,Et
CO,Et
(XLIV)
ETOHo
CH,—C CH,—C
/ \ ©OET / \
Me,C £°CH, < Me,C CH,
^CH C CHCO,Et
I !IX> • I
CO,Et O OEt CO,Et (XLVI) (XLV)o
CH,—C
/ \
Me,C CH,
\ /
CH—C
CO,Et O
(XLVII)CH,—C
(i) Hydrolysis
* > Me,C CH,
(ii) Decarboxylation /
Clf,—c
\
o
(XLI)and aliphatic nitro-compounds, e.g..CH 3 NOg. Thus in the formation
of dimedone (XLI) from diethyl malonate and mesityl oxide (XLII)
the carbanion (XLIII) derived from diethyl malonate attacks the
/3-carbon atom of mesityl oxide to yield the ion (XLIV), which is
converted, via its enol, to the ketone (XLV). This constitutes the
Michael reaction proper, i.e. the carbanion addition to an «j8-un-
saturated carbonyl compound. In this case, however, the reaction
proceeds further for (XLV) is converted by eOEt to the carbanion
(XLVI) which cyclises by expelling eOEt from the ester group (cf. the
Dieckmann reaction, p. 178) to yield (XLVII). Hydrolyai* and decar
boxylation of the j3-keto-ester then yields dimedone (XLI):