3,4-Dihydroisoquinolinium trichloroacetatochromate: A mild and effective new reagent for oxidation of alcohols to carbonyl compounds and arenes to their quinones

Article abstract of DOI:10.14233/ajchem.2014.16695

A new chromium(VI) reagent, 3,4-dihydroisoqinolinium trichloroacetatochromate was prepared by reacting trichloroacetic acid with CrO₃in water. This reagent is suitable to oxidize various primary and secondary alcohols to the corresponding carbonyl compounds and anthracene to antraquinone in a good yields.

Full text of DOI:10.14233/ajchem.2014.16695

Asian Journal of Chemistry; Vol. 26, No. 18 (2014), 6081-6083
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16695
3
,4-Dihydroisoquinolinium Trichloroacetatochromate: A Mild and Effective New Reagent for
Oxidation of Alcohols to Carbonyl Compounds and Arenes to Their Quinones
RECEP OZEN
Department of Chemistry, Faculty of Science, Mersin University, 33342, Mersin, Turkey
Corresponding author: Tel: +90 324 3610001; Fax: +90 324 36100046; E-mail: rozen@mersin.edu.tr
Received: 14 November 2013;
Accepted: 30 December 2013;
Published online: 1 September 2014;
AJC-15858
A new chromium(VI) reagent, 3,4-dihydroisoqinolinium trichloroacetatochromate was prepared by reacting trichloroacetic acid with
CrO in water. This reagent is suitable to oxidize various primary and secondary alcohols to the corresponding carbonyl compounds and
3
anthracene to antraquinone in a good yields.
Keywords: 3,4-Dihydroisoqinolinium trichloroacetatochromate, Oxidation, Alcohols.
INTRODUCTION
EXPERIMENTAL
The oxidation of organic substrates in aprotic solvents,
under mild and neutral contitions, is important in modern
organic synthesis. Therefore, the search for new oxidizing
Melting points were determined on Electrothermal 9100®
apparatus. IR spectra were recorded on a Win First Satellite®
model spectrophotometer. H NMR spectra were obtained
1
1
-7
agents is of interest to synthetic organic chemists . The
representative chromium-based reagents play a vital role in
using a 400 MHz Bruker DPX® instrument. Chromium
analyses were performed using UV-1601 Shimadzu® All
products are known compounds; they were identified by
comparision of their physical and spectral data with those of
authentic samples. All reagent and solvents are of reagent
grade. 3,4-Dihydroisoquinoiline was prepared according to
8
organic chemistry as oxidants for alcohols . For instance, the
9
10
Collins reagent , pyridinium chlorochromate , pyridinium
1
1
12
bromochromate , cerium(III) bromate , quinolinium fluoro-
13
chromate have been devoloped for this purpose. There are
several examples using supported organic molecules on solid
support as a oxidizing agents such as silica gel, montmorillonite
K10 .
Recently, we have introduced 3,4-dihydroisoquinolinium
16
literature .
Preparation of 3,4-dihydroisoqunolinium trichloro-
acetatochromate: A solution of CrO (5 g, 0.05 mol) in water
14
3
10 mL cooled to °C was added trichloroacetic acid (8.15 g,
0.05 mol) in 50 mL glass beaker. The mixture was stirred to
give an red-orange solution for 2-3 min. The solution was then
cooled in an ice bath (0-5 °C) for 5 min and 3,4-dihydroiso-
quinoline (6.58 g, 0.05 mol) was added portion wise and the
mixture was stirred at 0 °C for 1 h. The cold mixture was
filtered on a sintered glass funnel and the red-orange solids
were collected. The product was dried in vacuum desicator
chlorochromate (DIQCC).As an efficient reagent for oxidation
of alcohols to carbonyl compounds and arenes to their respec-
15
tive quinones .
In continuation of our study, we wish to report 3,4-dihydro-
isoquinolinium trichloroacetatochromate, a facile oxidation
reagent primary, secondary and benzylic alcohols to their
corresponding carbonyl compounds. At the same time, this
reagent was used for oxidizing various arenes such as indane,
tetraline, antracene, pheneanthrene compounds.
Some of the reported reagents suffer from disadvantages
such as instability, hygroscopicity, low selectivity, long reaction
time, difficulty of preparation and need for a large excess of
the reagent. Thus, a mild, a more selective and inexpensive
reagent is still in demand.
over P O
2 5
to give 3,4-dihydroisoquinolinium chlorochromate
in 90 % yield. The reagent decompeses at 100 °C. IR (KBr
-1
pellet) cm 3442, 3055, 1678, 1238, 962, 883. Anal. Calcd.
Cl Cr: C, 33.49; H, 2.55; N, 3.55. Found: C,
For C11
H10NO
5
3
33.20; H, 2.50; N, 3.60. The acidity of 3,4-dihydroiso-
quinolinium chlorochromate is at pH. 2.4 in 0.01 M aqua
solution.

6
082 Ozen
Asian J. Chem.
Oxidation of alcohols to carbonyl compounds:A solution
compound is diamagnetic tested by means of magnetic suscep-
tibility mesurement. The compound decomposes at 100 °C.
The molar conductance of 3,4-dihydroisoquinolinium chloro-
of the organic compounds (Table-1, 10 mmol) in 10 mL of
dichloromethane was added to 3,4-dihydroisoquinolinium
chlorochromate (Table-1, 1:1 ratio; 3.94 g, 10 mmol and 1:3
ratio; 11.83 g, 30 mmol). The mixture was stirred magneti-
cally at room temperature until the complete consumption of
the substrate. The progress of the reaction was monitored by
TLC analysis.After completion of the reaction, 50 mL of water
was added to the reaction mixture and extracted with ether
-1
2
-1
chromate in water at 25 °C is 140 Ω cm mol . The acidity of
3,4-dihydroisoquinolinium chlorochromate (pH of a 0.01 M,
solution 2.4) is less than that of PCC, (pH of a 0.01 M solution
11
14
1.75) and CPCC (pH of 0.01 M, solution 2.02) .
R1
R1
(
3 × 20 mL). The combined organic layer was dried over MgSO
4
and evaporated on a rotary evaporator under reduced pressure.
Then the product was chromatographed over silica gel using
ethyl acetate-hexane (1:4) as the eluent to separate the product.
After evaporation of the solvent, the fairly pure solid were
crytstallized out the liquid carbonyl compounds were deriva-
tized with 2,4-dinitrophenylhydrazine. The melting points of
solid compounds such as benzil, benzophenone, 3-oxocholes-
torol, 1-menthone, 1-indanone, tetralone, 10-anthraquinone
and phenanthrene-9,10-quinone were checked and these
DIQCAC, CH
2 2
Cl
CH
OH
C
O
Room temperature
2
2
R
R
1
2
R , R =alkyl,aryl, H
Scheme-I
This reagent can be stored as a solid for long periods
without decomposition in dry medium. The structure of 3,4-
dihydroisoquinolinium chlorochromate was determined by
infrared spectra and elemental analysis. The amount of
chromium(IV) was determined by colorimetric methods using
1
compounds were identified by spectral data like IR and H
NMR.
17
diphenylcarbazide solution .Anal. Calc. for C11
H
10NO
5
Cl Cr:
3
TABLE-1
OXIDATION OF ORGANIC SUBSTRATES WITH
Cr: 15.0 ; Calc. 15.01.
3
3
,4-DIHYDROISOQUINOLINIUM CHLOROCHROMATE
As can be seen from Table-1, various substrates were
tested with 3,4-dihydroisoquinolinium chlorochromate. 3,4-
Dihydroisoqinolinium trichloroace-tatochromate readily
oxidizes primary (entires 1 to 4) and secondary alcohols (entires
5 to 10) to their corresponding carbonyl compounds in an
excellent yield. 3,4-Dihydroisoqinolinium trichloroacetato-
chromate also oxidizes including benzylic carbon indan and
Substrate Time Yield
d
Entry
Substrate
n-Butanol
Product
/
Oxidant (h)
(%)
b
1
2
3
4
5
6
7
8
9
0
1
2
3
Butanal
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:3
1:3
1:3
0.5 98
0.5 90
0.5 85
0.5 90
0.5 93
b
Isoamylalcohol 3-Methylbutanal
1-Octanol Octanal
Benzyl Alcohol Benzaldehyde
b
b
b
2-Pentanol
Benzhydrol
2-Pentanone
18
tetralin (entires 11 to 12) those converted to ketones in a
c
Benzophenone
Cyclohexanol Cyclohexanone
Cyclopentanol Cyclopentanon
1
2
1
2
1
80
95
95
88
92
good yields. In order to ascertain the efficacy of the reagent
as an oxidant, it was treated with fused ring hydrocarbon
b
b
c
c
19
anthracene and phenanthrene (entires 13 to 14). Anthracene
and phenanthrene are oxidized to 9,10-anthraquinone and
phenanthrene-9,10-quinone, respectively in good to excellent
yields using substrate/oxidant ratio 1:3.
Cholesterol
1-Menthol
Indan
Tetralin
Anthracene
3-Oxocholesterol
1-Menthone
1-Indanone
1
1
1
1
c
c
c
2.5 85
2.5 75
1.5 85
Tetralone
9,10-
1
All products were characterized by H NMR and IR
Anthraquinone
spectroscopic data and their physical data compared with
c
1
4
Phenanthrene Phenanthrene-
,10-quinone
1:3
2.0 85
20
literature datas .
In conclusion, 3,4-dihydroisoquinolinium chlorochromate
9
Oxidations were carried out in dichloromethane at room temperature;
Yields refer 2,4-DNP derivatives identified by melting points; Yields
refer to isolated products melting points were taken directly and
comparison with authetic samples (IR, TLC and NMR)
c
is suitable, an inexpensive and stable solids. We have developed
a practical procedure for the oxidation of alcohols to corres-
ponding carbonyl compounds, of benzylic carbon to those
ketones and of arenes to their ketones. 3,4-Dihydroiso-
qinolinium trichloroacetatochromate can be easily prepared
and serves as an excellent oxidizing agent for various types of
alcohols, benzylic carbons and arenes under non-aqueous
condition at ambient temperature.After the oxidation reaction
by 3,4-dihydroisoquinolinium chlorochromate, working-up
such as filtration and extraction is fairly easy due to granula
reduces.
RESULTS AND DISCUSSION
This reagent was prepared by the addition of 3,4-
tetrahydroisoquinoline to a solution of an equimolar amount
of CrO and trichloroacetic acid at 0 °C and obtained in 90 %
16
3
yield as an orange solid. 3,4-Dihydroisoqinolinium trichloroac-
etatochromate was stable when kept at room temperature for
a long period of time. The infrared absorption frequencies for
the trichloroacetato group at 962, 883 and 722 cm . 3,4-
Dihydroisoqinolinium trichloroacetatochromate is soluble in
polar solvent such as water, dimethyl formamide, dimethyl
sulfoxide, acetone, ethylacetate, acetonitrile, but insoluble in
dichloromethane, benzene, carbon tetrachloride and ether. The
-
1
ACKNOWLEDGEMENTS
Author is greatful to Mersin University Research Council
and TUBITAK (The Scientific and Technical Council of Turkey
for the supporting this work (Grant No: TBAG-2235).

Vol. 26, No. 18 (2014)
Oxidation of Alcohols to Carbonyl Compounds and Arenes to Their Quinones 6083
1
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