Highly enantiomeric purity conversion of α-sulfinyl oximes and α-sulfinyl hydrazones to the corresponding β-keto sulfoxides with butyltriphenylphosphonium periodate (BUTPPPI)

Article abstract of DOI:10.1080/714040978

Butyltriphenylphosphonium periodate (Ph₃P₊BuIO ₄^-)1 is readily prepared as a white solid from butyltriphenylphosphonium chloride, performs conversion of α-sulfinyl oximes (2) and α-sulfinyl hydrazones (4) to the

Full text of DOI:10.1080/714040978

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Phosphorus, Sulfur, and Silicon and the Related
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Highly Enantiomeric Purity Conversion of α-Sulfinyl
Oximes and α-sulfinyl Hydrazones to the Corresponding
β-keto Sulfoxides with Butyltriphenylphosphonium
Periodate (BUTPPPI)
A. R. Hajipour a b & A. E. Ruoho b
a University of Wisconsin Medical School, Madison, Wisconsin, USA
b Isfahan University of Technology, Isfahan, Iran
Published online: 18 Jun 2010.
To cite this article: A. R. Hajipour & A. E. Ruoho (2003) Highly Enantiomeric Purity Conversion of α-Sulfinyl Oximes and α-
sulfinyl Hydrazones to the Corresponding β-keto Sulfoxides with Butyltriphenylphosphonium Periodate (BUTPPPI), Phosphorus,
Sulfur, and Silicon and the Related Elements, 178:12, 2653-2657, DOI: 10.1080/714040978
To link to this article: http://dx.doi.org/10.1080/714040978
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Phosphorus, Sulfur, and Silicon, 178:2653–2657, 2003
ꢀC
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500390248376
HIGHLY ENANTIOMERIC PURITY CONVERSION
OF α-SULFINYL OXIMES AND α-SULFINYL
HYDRAZONES TO THE CORRESPONDING
β-KETO SULFOXIDES WITH
BUTYLTRIPHENYLPHOSPHONIUM
PERIODATE (BUTPPPI)
A. R. Hajipoura,b and A. E. Ruohob
University of Wisconsin Medical School, Madison, Wisconsin,
USAa and Isfahan University of Technology, Isfahan, Iranb
Butyltriphenylphosphonium periodate (Ph3 P+ BuI O−) 1 is readily pre-
pared as a white solid from butyltriphenylphosphon4ium chloride, per-
forms conversion of α-sulfinyl oximes (2) and α-sulfinyl hydrazones (4)
to the corresponding β-keto sulfoxides (3) in high yields and high enan-
tiomeric purity.
Keywords: α-Sulfinyl hydrazones; α-sulfinyl oximes; β-keto sulfoxides;
chiral nonracemic synthesis; high enantiomeric purity
β-Keto sulfoxides are very important starting materials in asymmetric
synthesis,1,2 and can be synthesis by the cleavage of the C N bonds of α-
sulfinyl oximes and α-sulfinyl hydrazones. These compounds prepared
via the addition of aryl methyl sulfoxides to aryl N-oxides3 or the addi-
tion of lithiated N,N-dimethyl hydrazones to menthyl sulfinate esters4
respectively. The hydrolysis of C N double bond of α-sulfinyl oximes
(2) and α-sulfinyl hydrazones (4) by a classical method5 was attempted
but the optical purity and yield by this method were low (ee <35 and
yield <50%).
We gratefully acknowledge the funding support received for this project from the
Isfahan University of Technology (IUT), IR Iran (A.R.H.) and Grant GM 33138 (A.E.R.)
from the National Institutes of Health, USA. Further financial support from Center of
Excellency in Chemistry Research (IUT) is also acknowledged.
Address correspondence to A. R. Hajipour, Department of Pharmacology, University
of Wisconsin Medical School, 1300 University Ave., Madison, WI 53706-1532. E-mail:
arhajipour@facstaff.wisc.edu
2653

2654
A. R. Hajipour and A. E. Ruoho
RESULTS AND DISCUSSION
Butyltriphenylphosphonium periodate (Ph3P+BuIO−) is a mild, effi-
cient, stable, and inexpensive reagent, that has been4used for our stud-
ies under nonaqueous conditions. This reagent is a white powder, which
is prepared by the dropwise addition of an aqueous solution of NaIO4
to an aqueous solution of butyltriphenylphosphonium chloride at room
temperature. Filtration and drying of the precipitate produced a white
powder, which could be stored for months without losing its oxidation
ability. This reagent is quite soluble in polar solvents such as methylene
chloride, chloroform, acetone, and acetonitrile and insoluble in nonpo-
lar solvents such as carbon tetrachloride, n-hexane, and diethylether.
We found that the cleavage of C N double bond of α-sulfinyl oximes
(2) and α-sulfinyl hydrazones (4) by this reagent in acetonitrile under
reflux is rapid (50–70 min). The reaction is very fast and almost quan-
titative with high optical purity from 1H NMR analysis in the presence
of chemical shift reagent (>92) (Tables I and II). The general reac-
tion is detailed in Scheme 1. In all case, the crude product was judged
1
to be of >95% purity based on H NMR and TLC analysis. Because
of the mildness of the reagent, as shown in Tables I and II, the cor-
responding sulfones are not formed in these reactions. At this stage
the mechanism of the reaction is not clear to us. The enantiomeric pu-
rity of (3) was determined to be >92 from 1H NMR chiral shift studies
using (−)-(R)-N-(3,3-dinitrobenzoyl)-α-phenylethylamine (5) as a chi-
ral shift reagent6 and comparing the optical rotation of the products
TABLE I Conversion of (2) to the Corresponding Carbonyl
Compounds (3)
Starting material Product Reaction time/min Yield %a
e.e. %
2a
2b
2c
2d
2e
2f
2g
2h
2I
3a
3b
3c
3d
3e
3f
3g
3h
3I
50
55
60
55
65
65
55
55
70
96
95
98
95
99
97
99
96
96
92
95
98
100
100
99
96
97
97
aConfirmed by comparison with authentic samples (IR, TLC, and
1H-NMR).1−5
bSubstrate/reagent (1:1).
cYield of isolated pure product after purification.

Keto Sulfoxides
2655
SCHEME 1
with known compounds.1−5 To determine the enantiomeric purity of (3)
we mixed it with one equivalent of chiral shift reagent (5) in a NMR
tube.
In conclusion, we report here an efficient, rapid, mild, and inexpen-
sive method for the conversion of α-sulfinyl oximes (2) and α-sulfinyl
hydrazones (4) by butyltriphenylphosphonium periodate BuP+Ph3IO−
(1) in acetonitrile under refluxing conditions to the correspondin4g
β-keto sulfoxides (3).

2656
A. R. Hajipour and A. E. Ruoho
TABLE II Conversion of (4) to the Corresponding Carbonyl
Compounds (3)
Starting material Product Reaction time/min Yield %a
e.e. %
4a
4b
4c
4d
4e
4f
4g
4h
4I
3a
3b
3c
3d
3e
3f
3g
3h
3I
60
65
60
60
65
70
60
55
70
98
98
95
97
97
99
96
99
98
92
94
95
94
96
97
98
95
99
aConfirmed by comparison with authentic samples (IR, TLC, and
1H-NMR).1−5
bSubstrate/reagent (1:3).
cYield of isolated pure product after purification.
EXPERIMENTAL
General
All yields refer to isolated products after purification. Starting materi-
als were synthesis by known methods.1−5 Products were characterized
by comparison with authentic samples1−5 and by spectroscopy data
(IR, NMR spectrum, tin layer chromatography, melting and boiling
points). All reactions were carried out in acetonitrile. All m.p.s were
taken on a Gallenkamp melting apparatus and are uncorrected. Re-
search Institute of Petroleum Industry, Tehran, Iran performed ele-
mental analysis. 1H NMR spectra were recorded at 300 MHz. The spec-
tra were measured in CDCl3 unless otherwise stated, relative to TMS
(0.00 ppm). Optical rotations were recorded with a JASCO, DIP-370,
Digital Polarimeter.
Preparation of Butyltriphenylphosphonium
Periodate (1) (BTPPPI)
A solution of butyltriphenylphosphonium chloride (17.37 g, 49 mmol)
in 100 ml of water was prepared, then NaIO4 (10.49 g, 49 mmol) in
water (100 ml) was added dropwise to the above solution and stirred
for 30 min at room temperature. The resulting white precipitate was
filtered and washed with cooled distilled water (50 ml), and dried in a
desiccator under vacuum over calcium chloride to afford a white powder
(24.49 g, 98% yield), which decomposed at 150–153◦C to a dark brown
1
material. H-NMR: δ 7.89–7.72 (m, 15H), 3.23 (m, 2H), 1.68 (m, 4H),
0.92 (t, 3H). 13C NMR: δ 136.03, 136.00, 134.62, 134.54, 131.27, 131.17,

Keto Sulfoxides
2657
119.72, 119.04, 118.26, 24.92 (d, J = 298,5 Hz, C P). IR (KBr). Anal
Calcd for C22H24IO4P: C, 51.76; H 4.70%. Found: 52.00; H, 4.68%.
Oxidation of (2) or (4) to (3)
General Procedure
The α-sulfinyl oximes (2) or α-sulfinyl hydrazones (4) (1 mmol) was
added to a stirred solution of the oxidant (1) (1 mmol, 0.51 g) in ace-
tonitrile (20 ml). The mixture was heated at reflux until TLC showed
complete disappearance of starting material, which required 50–70 min
depending on substrate (Tables I and II). The mixture was cooled and
2 g of silica gel was added to the reaction mixture and the reaction
mixture was stirred for 5 min. The solid was then separated by suc-
tion filtration through Celite and washed with acetonitrile (2 × 10 ml).
Evaporation of the solvent gave the β-keto sulfoxides (3). The crude
products were purified by column chromatography on silica gel using a
mixture of ethyl acetate and hexane as eluent (90:10).
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[4] A. R. Hajipour and N. Mahboubkhah, J. Chem. Research (S), 122 (1998).
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