CERIUM(IV) AMMONIUM SULFATE 1
Ph
Cerium(IV) Ammonium Sulfate1
CAS, 50 °C, 4 h
H2SO4, MeCN
O Ph O
Ce(NH4)4(SO4)4 · 2H2O
Ph
(2)
+
(·2H2O)
[7637-03-8] CeH16N4O16S4 (MW 596.52)
O O
InChI = 1/Ce.4H3N.4H2O4S/c;;;;;4*1-5(2,3)4/h;4*1H3;4*(H2,
24% 28%
1,2,3,4)/q+4;;;;;;;;/p-4/fCe.4H4N.4O4S/h;4*1H;;;;/qm;
4*+1;4*-2
Oxidation of 1,4-diphenylnaphthalene gives 2,3-diphenyl-
InChIKey = OKJMLYFJRFYBPS-PMNQXKOTCT
1,4-naphthoquinone or 4-hydroxy-2,4-diphenyl-1(4H)-naphtha-
[10378-47-9] H20CeN4O18S4 (MW 632.55)
lenone, depending upon the reaction conditions (eq 3).5
InChI = 1/Ce.4H3N.4H2O4S.2H2O/c;;;;;4*1-5(2,3)4;;/h;4*1H3;
4*(H2,1,2,3,4);2*1H2/q+4;;;;;;;;;;/p-4/fCe.4H4N.
O
4O4S.2H2O/h;4*1H;;;;;;/qm;4*+1;4*-2;;
Ph
CAS, 50 °C
InChIKey = VCNAMBGKEDPVGQ-LFZNXPSQCB
6M H2SO4, MeCN
Ph
68%
Ph
(convenient reagent for oxidation of aromatic rings,2 and
O
halophenols to quinones,6 for regioselective Baeyer Villiger
(3)
oxidation,11 and oxidative aromatization12)
O
Alternate Name: ceric ammonium sulfate; CAS.
Ph
Ph
ć%
Physical Data: mp 140 C (dec).
CAS, 50 °C
Solubility: sol water, dil. H2SO4, dil. H2SO4 MeCN.
0.5M H2SO4, MeCN
52%
Form Supplied in: orange solid, widely available.
HO Ph
Handling, Storage, and Precautions: cerium(IV) ammonium sul-
fate is a stable reagent and precautions required for handling
A process utilizing catalytic amounts of CeIV and AgII has also
strong oxidizing agents such as Potassium Permanganate will
been reported (eq 4).6
be sufficient. Cerium is reputed to be of low toxicity.
Unfortunately, this reagent system is not suitable for the oxi-
dation of substrates of higher ionization potential nor for oxygen-
substituted compounds.
Cerium(IV) ion is a potent one-electron oxidant.1 Cerium(IV)
Ce4+, Ag2+, SDS
Ammonium Nitrate (CAN), is the most widely utilized
cerium(IV) oxidizing agent, but cerium(IV) ammonium sulfate
S2O82 , 73%
O
O
(CAS) is a good substitute when complications due to the in-
volvement of nitrate ligands occur, resulting in side products such
+ (4)
as nitrate esters.1
O
O
Synthesis of Quinones by Oxidation of Aromatic Rings.
The most important application of CAS is in the oxidation of
aromatic rings. CAN oxidizes polycyclic aromatic hydrocarbons The major product isolated from the reaction of CAS with
only in moderate yields (20 60%),1 and these reactions are of- benzo[b]fluoranthene is a lactone (eq 5).7
ten complicated by the formation of nitrate esters.2 In contrast,
O O
CAS generally oxidizes aromatic hydrocarbons to quinones in
CAS, H2SO4
good yields. For example, naphthalene is oxidized to 1,4-naphtho-
MeCN, 3 h, rt
quinone in excellent yield by CAS in a dilute mixture of H2SO4
(5)
53%
and MeCN (eq 1).3
O
O
CAS, 25 °C, 6 h
(1)
Oxidation of Phenols to Quinones. Halophenols are conve-
H2SO4, MeCN
90 95% niently oxidized by CAS to haloquinones in good yields (eq 6).8
O
On oxidation with CAS, halonaphthols furnish 1,2-diones as
minor products in addition to 1,4-quinones.
Other polycyclic aromatic hydrocarbons such as phenanthrene,
anthracene, and fluoranthene are converted to the corresponding OH O
R1 Br R1 Br
quinones on oxidation with CAS. Whereas 1-methylnaphthalene
Ce4+, rt
(6)
gives 1-naphthaldehyde under the conditions,3 1-phenyl- and
H2SO4, MeCN
R2 R3 R2 R3
1-bromonaphthalene react to form some 2-substituted naphtho-
Br O
quinones through an interesting rearrangement (eq 2).4
Avoid Skin Contact with All Reagents
2 CERIUM(IV) AMMONIUM SULFATE
O OR
A direct and convenient route for the conversion of gentisic acid
to the corresponding quinone has been developed through the use
CAS, I2
+ ROH (9)
of CAS in CHCl3 (10% within 15 min) (eq 7).9
10 h, ", 51%
OH O
CO2H CO2H
CAS, CHCl3
(7)
1. (a) Ho, T. L. Synthesis 1973, 347. (b) Beletskaya, I. P.; Makhankov,
rt
R R
D. I. Russ. Chem. Rev. (Engl. Transl.) 1981, 50, 534.
OH O
2. Rindone, B.; Scolastico, C. J. Chem. Soc. (B) 1971, 2238.
3. Periasamy, M.; Bhatt, M. V. Synthesis 1977, 330.
4. Periasamy, M.; Bhatt, M. V. Tetrahedron Lett. 1977, 2357.
Baeyer Villiger Oxidation. Oxidation of 1,3-bishomocuba-
5. Bhatt, M. V.; Periasamy, M. Tetrahedron 1994, 50, 3575.
none with a slurry of CAS gives rise to the corresponding lactone
6. Sharzewski, J. Tetrahedron 1984, 40, 4997.
(eq 8),10 which is obtained only as a minor product in the peroxy
7. Balanikas, G.; Hussain, N.; Amin, S.; Hecht, S. S. J. Org. Chem. 1988,
acid Baeyer Villiger oxidation conditions.
53, 1007.
8. Gopinathan, M. B.; Bhatt, M. V. Indian J. Chem., Sect. B 1981, 20B, 71.
CAS, aq MeCN
(8)
9. Holmes, Jr., J. T.; Vennerstorm, J. J.; Choi, K. E. J. Org. Chem. 1984,
60 °C, 1 h, 78%
49, 4736.
O
O 10. Mehta, G.; Pandey, P. N.; Ho, T. L. J. Org. Chem. 1976, 41, 953.
O
11. Makhonkov, D. I.; Cheprakov, A. V.; Rodkin, M. A.; Beletskaya, I. P.;
Zh. Org. Khim. 1986, 22, 1117 (Chem. Abstr. 1988, 108, 5616p).
Oxidative Halogenation. The reaction of RPh (R = H, 12. Horiuchi, C. A.; Fukunishi, H.; Kajita, M.; Yamaguchi, A.; Kiyomiya,
H.; Kiji, S. Chem. Lett. 1991, 1921.
Cl, Br, I, Me) with Potassium Iodide in CF3CO2H containing
CAS gives a mixture of 2- and 4-RC6H4I. Oxidation of methyl
Mariappan Periasamy & Ukkiramapandian Radhakrishnan
4-methylbenzoate with CAS under the reaction conditions gives
University of Hyderabad, Hydrabad, India
exclusively methyl 3-iodo-4-methylbenzoate.11
Oxidative Aromatization. A new type of oxidative aromati-
zation of cyclohexenone with the CAS Iodine system has been
developed (eq 9).12
A list of General Abbreviations appears on the front Endpapers