Dichloro (5,10,15,20-tetraphenylporphyrin) phosphorus(V) chloride as a new catalyst for conversion of 1,2-epoxyethanes to 2-hydroxyethyl thiocyanates with ammonium thiocyanate

Article abstract of DOI:10.1080/10426500490484995

A convenient and efficient procedure for the cleavage of the oxirane rings with ammonium thiocyanate in the presence of phosphorus(V)tetraphenylporphyrin is described. The ring-opening of 1,2-epoxyethanes is found to proceed regioselectively under mild reaction conditions. Thus, several 2-hydroxyethyl thiocyanates, useful intermediates toward biologically active molecules, are easily obtained in very good yields.

Full text of DOI:10.1080/10426500490484995

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DICHLORO (5,10,15,20-
TETRAPHENYLPORPHYRIN)
PHOSPHORUS(V) CHLORIDE
AS A NEW CATALYST FOR
CONVERSION OF 1,2-
EPOXYETHANES TO 2-
HYDROXYETHYL THIOCYANATES
WITH AMMONIUM THIOCYANATE
Hashem Sharghi a & Alireza Hassani Nejad a
a Department of Chemistry, College of Sciences,
Shiraz University, Shiraz, I. R. Iran
Published online: 16 Aug 2010.
To cite this article: Hashem Sharghi & Alireza Hassani Nejad (2004) DICHLORO
(5,10,15,20-TETRAPHENYLPORPHYRIN) PHOSPHORUS(V) CHLORIDE AS A NEW CATALYST
FOR CONVERSION OF 1,2-EPOXYETHANES TO 2-HYDROXYETHYL THIOCYANATES WITH
AMMONIUM THIOCYANATE, Phosphorus, Sulfur, and Silicon and the Related Elements,
179:11, 2297-2305, DOI: 10.1080/10426500490484995
To link to this article: http://dx.doi.org/10.1080/10426500490484995
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Phosphorus, Sulfur, and Silicon, 179:2297–2305, 2004
ꢀC
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490484995
DICHLORO (5,10,15,20-TETRAPHENYLPORPHYRIN)
PHOSPHORUS(V) CHLORIDE AS A NEW CATALYST
FOR CONVERSION OF 1,2-EPOXYETHANES
TO 2-HYDROXYETHYL THIOCYANATES
WITH AMMONIUM THIOCYANATE
Hashem Sharghi and Alireza Hassani Nejad
Department of Chemistry, College of Sciences,
Shiraz University, Shiraz, I. R. Iran
(Received February 25, 2004; accepted April 5, 2004)
A convenient and efficient procedure for the cleavage of the oxi-
rane rings with ammonium thiocyanate in the presence of phos-
phorus(V)tetraphenylporphyrin is described. The ring-opening of 1,2-
epoxyethanes is found to proceed regioselectively under mild reaction
conditions. Thus, several 2-hydroxyethyl thiocyanates, useful interme-
diates toward biologically active molecules, are easily obtained in very
good yields.
Keywords: Epoxide; porphyrin; thiocyanohydrine
INTRODUCTION
Epoxides or oxirans are versatile intermediates in organic synthesis,
and a large variety of reagents are known for the ring opening of these
compounds.1,2 The reaction of thiocyanate ion with epoxides has been
widely studied. Synthetic access by oxirane ring opening with thio-
cyanate ion has been limited by a further reaction to give thiiranes.3,4
There are two methods reported in the literature for the synthesis
of 2-hydroxyethyl thiocyanates. In one method, 2-hydroxyethyl thio-
cyanates are prepared by opening a cyclic sulfate with NH4SCN to form
the corresponding β-sulfate, which is hydrolyzed to the 2-hydroxyethyl
thiocyanates. A second method employs the addition of thiocyanic acid
We gratefully acknowledge the support of this work by the Shiraz University Research
Council and Dr. M. A. Nasseri, Dr. B. Hemmateenejad, and Dr. R. Ghavami for their
helpful comments.
Address correspondence to Hashem Sharghi, Department of Chemistry, College of
Sciences, Shiraz University, Shiraz 71454, I. R. Iran. E-mail: shashem@chem.susc.ac.ir
2297

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2298
H. Sharghi and A. H. Nejad
generated in situ at low temperature5 to the 1,2-epoxyethanes. For
these syntheses it has been reported that the presence of some hydro-
quinone or DDQ is required to stabilize the produced 2-hydroxyethyl
thiocyanates and inhibit its conversion to thiirane.6 Although the
reagents, such as Ph3P (SCN)2,7 Pd (PPh3)4,8 Ti (O-iPr)4,9 TMSNCS
(Cat. TBAF),10 and TiCl3 (or ZnCl2),11 are useful, they are limited to spe-
cific oxiranes and are not applicable as versatile reagents in preparation
of 2-hydroxyethyl thiocyanates.10
RESULT AND DISCUSSION
Although metalloporphyrins have been recognized as one of the most
promising catalysts for various reactions,12 a literature survey shows
that less attention has been paid to the use of nonmetal porphyrins
as new catalysts in organic synthesis. Phosphorus(V)porphyrin, with
a central six-coordinated phosphorus, is both a unique nonmetal
porphyrin13 and an unusual hypervalent compound with a large
π-electron system.14 The electrochemical behavior, redox chemistry,
photochemistry, and structure of phosphorus porphyrins have been
reported,15 and new conducting materials and chemotherapeutic agents
have been found.16
In conjunction with the ongoing work in our laboratory on the new
synthesis of meso-tetraarylporphyrins,17 complex formation of met-
alloporphyrins with different molecules,18 and anion-selective mem-
brane electrodes based on phosphorus(V)porphyrins,19 we found that
phosphorus (V) tetraphenylporphyrin ([P(TPP)Cl2]Cl) efficiently cat-
alyzed the addition of ammonium thiocyanate to oxiranes to form
2-hydroxyethyl thiocyanates with regioselectivity under mild reaction
conditions. The results of the reaction of styrene oxide with thiocyanate
ion in the presence of the [P(TPP)Cl2]Cl in various solvents are sum-
marized in Table I. The reaction product was 2-hydroxy-2-phenylethyl
thiocyanate, and the yield was determined by GLC and thin layer chro-
matography (TLC) analyses. We found out that the reaction appeared
to be largely dependent on the nature of solvent, and CH3CN was the
best solvent for this reaction. The optimum amount of the catalyst was
found to be 0.01 equiv versus epoxides.
As shown in Table I, yield of thiocyanation with this new methodology
is quite good and the reaction time is very short. However, the cleav-
age of the styrene oxide with ammonium thiocyanate in CH3CN in the
absence of catalyst was checked. Without the catalyst, the reaction re-
quired a much longer time. Moreover, undesirable thiirane-formation
predominated.20