6
K. Khosravi, S. Naserifar / Tetrahedron xxx (2018) 1e9
Table 6
1.6. Bayer-Villiger reaction (Scheme 2, entry 7)
Bayer-Villiger oxidation of ketones by THPDPE.a
Bayer-Villiger reaction of cyclic ketones producing esters [52] or
optically active lactones [53] has a large applicability in organic
synthetic chemistry to afford steroids, antibiotics, pheromones and
monomers for polymerization reactions [54]. Hydrogen peroxide in
presence of various catalysts including selenium (IV) oxide, aryl
seleninic acids [55,56] and peroxy acids [52] has undergone the
reaction. Yet, to overcome the weaknesses namely harsh reaction
conditions, low yields, expensive catalysts and products isolation
difficulties, more investigations are required to be conducted.
Consequently, we aimed to evaluate the oxidative potential of
THPDPE in Bayer-Villiger reaction oxidation of ketones and aro-
matic aldehydes in absence of any metals.
Entry
7a
Substrate
Product
Time (h)
2.5
Yield (%)b
81
7b
2
90
First, cyclohexanone was chosen as the substrate and after
assessing a number of solvents, bases, different amounts of oxi-
dants at different temperatures the following conditions were
finally selected as the optimized reaction conditions via which
oxepane-2-one was afforded rapidly: ketone (1 mmol), KHCO3
(1 mmol), THPDPE (1 mmol), MeCN (4 mL), 40 ꢀC.
7c
0.5
1.6
93
94
7d
Second, in an attempt to evaluate the oxidative potential of
THPDPE, Baye-Villiger oxidations of different ketones were per-
formed under the optimized reaction conditions. As the result,
corresponding lactones were produced in high yields. The gathered
results demonstrated that in more alkyl substituted cyclic ketones,
alkyl groups were able to migrate easier than other functionalities.
Besides, the presented strain in cyclobutanone, its reaction pro-
ceeded in a short time and dihydrofurane-2(3H)-one was yielded
(see Table 6).
7e
7f
1.3
9
91
86
1.7. Bromination of anilines and phenol derivatives (Scheme 2,
entry 8)
7g
7h
12
12
85
80
Aryl halides are chemicals with a wide range of applications
since they are present in numerous natural products [57,58]. Aryl
bromides can be synthesised using a number of methods such as
sandmeyer reaction [59], elemental bromination [60] and regio-
selective nuclear bromination applying NBS with tetrabuty-
lammonium or dioxane dibromide [61]. Though, due to the
limitations reported in the previous approaches have yet to be
discovered.
In our present approach, the investigation started with opti-
mizing the reaction conditions. To our delight, the best result was
achieved when using substrate (1 mmol), oxidant (0.5 mmol;
1 mmol for entry 5a, 5m and 5n), MeCN (4 mL) at room
temperature.
Next, the scope of the reaction was studied applying a series of
substituted anilines under the optimized reaction conditions. The
summarized data in Table 7 demonstrated that short reaction times
and higher yields were obtained in case anilines with electron-
donating groups underwent the reactions (Table 7, entries 8g and
8h), while electron-withdrawing substituted substrates performed
the reaction in longer times (Table 7, entries 8i, 8j, 8k and 8q). The
mentioned directory effect was obvious in all of the substrates in
Table 7. Furthermore, p-brominated aniline was yielded due to the
steric effect of nitrogen atom (Table 7, entry 8i). Eventually our
interesting finding was that the current procedure was chemo-
selective since Me, NO2, CHO and CN groups did not involve in the
reaction (Table 7, 8g-8k and 8q).
a
Conditions: ketone: 1 mmol, KHCO3 (1 mmol), peroxide (1 mmol), MeCN (4 mL),
40 ꢀC.
b
Isolated yields.
auxiliary agents, protecting groups, ligands in metal complexes and
catalysts and oxidants [63]. They are used in the synthesis of ag-
rochemicals and pharmaceuticals [62]. The previous reported
methodologies involved several drawbacks such as corrosive
agents, excessive solvents and by-products production. Conse-
quently, much more effort is required to be carried in order to
introduce new routes.
In 2015 Azarifar et al. [64], evaluated the oxidative potency of
THPDPE in oxidation of pyridines to N-Oxides under mild, catalyst-
free and solvent-free conditions at room temperature.
1.9. Oxidative esterification (Scheme 2, entry 10)
Ester functionality can be found in fragrances, pharmaceuticals,
polymers, agrochemicals and dyes [65]. They are also used as
building blocks in organic synthetic strategies and natural products
[66]. The direct transformation of aldehydes to esters has been a
convenient method and a lot of effort has been directed toward its
synthesis [67].
1.8. Oxidation of pyridines to N-Oxides (Scheme 2, entry 9)
Pyridine N-oxides possessing a dominant application as syn-
thetic intermediates and biological synthetic significance are clas-
sified as fine chemicals [62]. In addition, heterocyclic PNOs serve as
In the present work, evaluation of THPDPE started with exam-
ination through several parameters which led to the choice of
Please cite this article in press as: K. Khosravi, S. Naserifar, 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane: An efficient and high oxygen content