1052
Chemistry Letters Vol.37, No.10 (2008)
Highly Selective Production of 2-Adamantanone by Photocatalytic Oxidation of Adamantane
Sun-Jung Song,1 Kyoung Seok Kim,1;2 Kyung Hwan Kim,1;2 Jong Beom Kim,3 Jong-Ho Kim,1;2;3
Keun-Sik Kim,4 Honghyun Shin,5 and Dong Lyun Choꢀ1;2
1Center for Functional Nano Fine Chemicals, Chonnam National University, Gwangju 500-757, Korea
2Center for Photonic Materials and Devices, Chonnam National University, Gwangju 500-757, Korea
3Photo & Environmental Technology Co., Ltd., Gwangju 500-460, Korea
4KS Laboratories, Sunchon 540-856, Korea
5Daelim Chemical Co., Ltd., Jinju, Korea
(Received July 9, 2008; CL-080678; E-mail: dlcho@chonnam.ac.kr)
2-Adamantanone was selectively produced by photocatalyt-
ic oxidation of adamantane in acetic acid using TiO2 powders.
The reactions were carried out at ambient and acetic acid reflux
temperatures with and without an oxidant. Adding oxidant in
refluxing acetic acid under irradiation remarkably increased
conversion and selectivity. Rutile TiO2 powders showed better
conversion and selectivity in the presence of H2O2. The total
conversion was 67% and the highest selectivity of 2-adamanta-
none was 89%.
& Environmental Technology Co.). The ratio of anatase:rutile
in PC-100, P-25, and RT-1 was 100:0, 75:25, and 0:100, respec-
tively. 30% H2O2 or O3 was used as an oxidant.
O
TiO2/H2O2/h
ν
ð1Þ
acetic acid
(ADH)
(2-ADO)
The reactions were carried out in a 500-mL three-neck photo-
chemical reactor equipped with a reflux condenser. After ADH
(10.0 g, 0.07 mol) was dissolved in acetic acid (150 mL,
2.50 mol), TiO2 powders (1.0 g/10.0 g of ADH), and 30% H2O2
(40.0 mL) were added. The solution was then irradiated with a
150-W Hg-lamp for 10 h at ambient temperature or refluxing
acetic acid. After irradiation, the solution was kept at room tem-
perature in acetic acid for 10 additional hours to raise selectivity
for 2-ADO through further oxidation and disproportionation.
Compounds in the product were identified by comparing
with the GC chromatograms (Agilent 5890 series 2) of authentic
compounds. Conversion and selectivity of the reaction were
calculated based on the GC chromatograms.
It was observed that conversion of ADH and selectivity
for 2-ADO in the TiO2-photocatalyzed oxidation reactions were
dependent on the type of TiO2 powders. Figure 1 shows the con-
versions and selectivities for 3 different types of TiO2 powders.
Reactions were carried out at acetic acid reflux with 30% H2O2
as an oxidant. RT-1 shows the highest conversion and selectivity
and PC-100 the lowest, indicating that the rutile structure has a
higher photocatalytic activity than the anatase structure in this
reaction. This result is consistent with previously reported results
on the oxidation reactions of ADH in the presence of TiO2
2-Adamantanone (2-ADO) and 2-adamantanol (2-ADOH)
are useful oxidative derivatives of adamantane (ADH). In partic-
ular, 2-ADO is an important intermediate used for various phar-
maceuticals such as neurological disorder drugs and therapeutic
drugs for influenza.1,2 Recently, the demand for 2-ADO has
increased given its application in optical materials such as pho-
toresists and functional materials for heat resistant plastics.1,2
However, selective production of 2-ADO is difficult since it
can only be obtained by oxidation of one of the most stable hy-
drocarbon compounds, ADH. In addition, several complicated
steps are required to separate it from other oxidized products
produced together with 2-ADO from this oxidation process,
including 1-adamantanol, 2-adamantanol, 1,3-adamantanediol,
and 1-hydroxy-4-adamantanone.3,4 Among various developed
processes for the selective production of 2-ADO, only one proc-
ess in which ADH reacts with concentrated sulfuric acid at an
elevated temperature was adapted as a commercial process.
However, conversion is not high enough (ꢁ50%) to be an eco-
nomical process and separation and refinement of the products
is still required. This is coupled with the various environmental
and safety problems caused by the use of large amounts of 98%
H2SO4 at high temperatures. As a consequence, improvement of
the oxidation process has been attempted by using heterogene-
ous oxidative catalysts instead of concentrated sulfuric acid.5–7
Recently, it was reported that TiO2 photocatalytic oxidation of
C–H bonds in alkanes and cyclic alkanes could produce alcohols
or ketones,8 with TiO2-photocatalyzed oxidation of adamantane
attempted to confirm potential of photo-oxidation capability of
TiO2.9,10 However, the selectivity for 2-ADO was poor, as low
as 10%, because other oxidized mixtures were obtained together
with 2-ADO, however, TiO2 showed photo-oxidation capability.
In this study, the photocatalytic oxidation reaction of ADH with
TiO2 powders was attempted to selectively produce 2-ADO
(eq 1). Photocatalytic oxidations of ADH (Wako Pure Chemical
Industry Co.) were carried out with three types of TiO2 powders:
PC-500 (Millennium Co.); P-25 (Degussa Co.); and RT-1 (Photo
100
Conversion
Selectivity for 2-ADO
80
60
40
20
0
PC-500
P-25
RT-1
Figure 1. Conversions and selectivities of 2-ADO for 3 differ-
ent types of TiO2 powders by photocatalytic oxidation of ADH.
Copyright Ó 2008 The Chemical Society of Japan