Chemistry Reference
In-Depth Information
OH
1) ZnEt
2
, THF, rt, 5 h
t
Bu-P4 base (30 mol%)
Ph
2) PhCHO, -40 ˚C to rt, 17 h
CO
2
Et
78%
CO
2
Et
1) ZnEt
2
, THF, rt, 5 h
t
Bu-P4 base (30 mol%)
I
O
2)
O
CO
2
Et
Ph
Ph
Ph
Ph
71%
0 ˚C to rt , 10 h
1) ZnEt
2
, DMF, rt, 5 h
t
Bu-P4 base (5 mol%)
CO
2
Et
2) allyl bromide, rt, 20 h
98%
Scheme 5.38
Functionalization of arylzinc derivatives
1) ZnEt
2
, DMF, rt, 5 h
t
Bu-P4 base (5 mol%)
I
Ph
2) PhI, Pd(Ph
3
P)
4
, rt, 7 h
EtO
2
C
EtO
2
C
53%
Scheme 5.39
Negishi coupling of arylzinc compound
2-fluoronitrobenzene using Et
3
SiH/cat.
t
Bu-P4 at 80
C for 1 h, and the arylation was found
to proceed smoothly to give the arylmalonate in 99% yield (Table 5.11, run 1). The reaction
with diethyl malonate was found to be slower and the arylmalonate was obtained in 56%
yield after reacting for 22 h (run 2). Other
-substituted malonates also reacted with
2-fluoronitrobenzene to give arylmalonates (runs 3, 4).
a
a
-Substituted cyanoacetate and
a
-substituted malononitrile were also found to be excellent C-nucleophiles (runs 5, 6).
4-Fluoronitrobenzene reacted with methylmalonate to give the arylmalonate in 97% yield
(run 7). The less reactive 2-fluoro- and 4-fluorobenzonitrile also reacted with methylma-
lonate to give the corresponding arylmalonates in 46% and 66% yield, respectively (runs
8, 9). Conventionally, aryl fluorides with weak electron-withdrawing groups have not been
used for S
N
Ar reaction with these C-nucleophiles, and the method provides a new and
highly effective S
N
Ar reaction protocol [55].
