Chemistry Reference
In-Depth Information
Table 3.11 Reaction of p-nitroanisole and bismuth shots under different
conditions.
Product ratio
a
(a/b, Scheme 3.18)
Condition
Conversion (%)
Under air
78/22
B
100
Under air
b
100/0
7
Under N
2
17/83
B
100
Under O
2
100/0
B
100
1 Drop of hexane added
100/0
91
1 Drop of benzene added
100/0
B
100
a
Determined by
1
HNMR.
b
Powdery bismuth (
B
100 mesh) was used.
Bi
Bi
O
B
i
Bi
Bi
Bi
Ar
N
O
N
Ar
Ar
N
O
ArN
O
O
O
Bi
Bi
Bi
Bi
Bi
Bi
O
B
i
Bi
O
ArNNAr
O
Ar
N
NAr
Ar
N
N
Bi
Bi
Ar
O
Scheme 3.19 Proposed pathway for the deoxygenative dimerization of nitroarenes.
1) m.m. (14.6 Hz)
r.t.; > 4 h
2) acidic quenching
O
HO
OH
R
Ph/R
R
R/Ph
Ph
R
Ph
Ph/R
Ph
R/Ph
R = Ph, Me
Scheme 3.20 Mechanochemical reactions of benzophenone and acetophenone
with Mg.
species and further reduction is suppressed. Otherwise, the reaction pro-
ceeded further to produce azoarenes (Scheme 3.19).
23
The direct mechan-
ochemical reactions of benzophenone and acetophenone with Mg (4 eq.) have
been explored by Harrowfield et al., who found that the reaction included
coupling products to give pinacol, alkene and alkane species, as well as
simple reduced species.
24
After acid quenching, benzophenone provided
1,1,2,2-tetraphenylethanediol, tetraphenylethene and 1,1,2,2-tetraphenyl-
ethane as the main products, along with small quantities of diphenyl-
methanol and diphenylmethane. Acetophenone principally gave cis-and
trans-2,3-diphenylbut-2-ene plus meso-andrac-2,3-diphenylbutane-2,3-diol, as
well as some 1-phenylethanol (Scheme 3.20). Moreover, the replacement
of Mg with other metals (Al, Fe, Ti and Zn) led to much slower reactions and
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