Chemistry Reference
In-Depth Information
5 mol% Pd(OAc)
2
2.5 equiv. NaHCO
3
0.2 equiv. HCO
2
Na
1.2 equiv. TBAC
NaCl
PBM
800 min
-1
, 1 h
R
4
I
R
4
CO
2
CH
3
CO
2
CH
3
+
R
3
R
1
NHBoc
NHBoc
R
3
R
1
R
2
R
2
R
1
= H, NH
2
,
CH
3
,
OH
R
2
= H, NH
2
,
CH
3
R
3
= H, NH
2
,
CF
3
,
OH
R
4
= H, NH
2
,
CN, F, CO
2
CH
3
Scheme 2.8 Mizoroki-Heck reaction of iodoanilines.
5 mol% Pd(OAc)
2
3 equiv. K
2
CO
3
0.2 equiv. HCOONa
PEG
MBM
30 s
-1
,
1 h
I
+
CO
2
tBu
CO
2
tBu
Scheme 2.9 Mizoroki-Heck reaction using ball milling in poly(ethylene glycol)
(PEG).
0.5 mol% Pd(OAc)
2
1 equiv. TBAB
2.4 equiv. K
2
CO
3
silica gel
PBM
1290 min
-1
,
45-60 min
X
+
R
2
R
1
R
2
R
1
X = Br, Cl
R
1
= H, 4-CO
2
C
2
H
5
,
4-CH
3
,
4-OCH
3
,
3-F, 3,4,5-(F)
3
,
3-NO
2
,
4-NO
2
,
3-Ac, 4-CHO
R
2
= H, 3,4-(OCH
3
)
2
, 3,5-(OCH
3
)
2
, 3-OCH
3
, 4-Cl
Scheme 2.10 Mizoroki-Heck reaction with silica gel as milling auxiliary in a planet-
ary ball mill (PBM).
Su and co-workers have described the Mizoroki-Heck coupling using
tetra-n-butylammonium bromide (TBAB), K
2
CO
3
as base and silica gel as
milling auxiliary in a planetary-centrifugal mill AGO-2 to synthesize (E)-
stilbenes (Scheme 2.10).
24
Moderate to very good isolated yields (67-92%)
were achieved after 45-60 min milling with a 5 min pause every 15 min.
Without milling auxiliary only 19% yield of
the desired stilbene was
obtained.
2.3 Homo-coupling Reactions
2.3.1 Homo-coupling of Phenols
Binaphthols have a wide range of application. They are used in processes for
dyes, pigments, fluorescent whiteners or as antioxidants or antiseptics.
25
Furthermore they are useful as chiral auxiliaries or catalysts.
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