Handbook of Functionalized Organometallics Applications in S

8.2 gem-Dizincio Compounds
(Scheme 8.31). Although palladium catalyst helps the formation of 1,3-diketones
from acyl chloride and 4, an activation of 4 with tetrahydrothiophene (THT) shows
the better effect (Scheme 8.33) [19a].
R
O
CN
CH2(ZnI) 2
4
R
CN
R CH2ZnI O R R
O
O O
Ph CN n-C8H17 CN
O
C2H5OC(CH2) 2 CN
O (90%) O (85%)
O (85%)
Scheme 8.31 1,3-Diketone synthesis from acyl cyanide and 4.
O
+ PhCOCl
ZnI 2
25 ºC
O
Ph O
Scheme 8.32 Ring opening of tetrahydrofuran.
R
O
Cl
CH2(ZnI) 2
4
THF/THT
Ph Cl
O
Cl
O (98%) O (96%)
O
Cl
(71%)
Ph
R
22 99 %
Cl
R CH2ZnI O R R
O
O O
O
Cl
(58%)
CH3
S
I
O
O
Cl
Cl
(82%)
(52%)
Scheme 8.33 Preparation of 1,3-diketones from acyl chloride and 4 in THF/THT.
8.2.7
1,4-Addition of bis(iodozincio)methane to a,b-unsaturated ketones
Aconjugated addition of organozinc reagents to a,b-unsaturated carbonyl compound
has been well studied in the presence of various catalysts. If this reaction is
possible with bis(iodozincio)methane, the transformation gives c-zinc substituted
enolate. As shown in Scheme 8.34, bis(iodozincio)methane reacts with s-cis
a,b-unsaturated ketone in the presence of chlorotrimethylsilane to afford a silyl
365