Efficient conversion of tetrahydropyranyl (THP) ethers to their corresponding cyanides with triphenylphosphine/2,3-dichloro-5,6- dicyanobenzoquinone/n-Bu4 NCN

Article abstract of DOI:10.1080/10426500490466463

Tetrahydropyranyl ethers were converted to their corresponding alkyl cyanides efficiently by using the triphenylphosphine/ 2,3-dichloro-5,6- dicyanobenoquinone / n-Bu₄ NCN system in refluxing acetonitrile with good-to-excellent yields.

Full text of DOI:10.1080/10426500490466463

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Phosphorus, Sulfur, and Silicon and the Related
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EFFICIENT CONVERSION OF TETRAHYDROPYRANYL
(THP) ETHERS TO THEIR CORRESPONDING CYANIDES
WITH TRIPHENYLPHOSPHINE/2,3-DICHLORO- 5,6-
DICYANOBENZOQUINONE/n-Bu4 NCN
Batool Akhlaghinia a
a Department of Chemistry, Damghan University of Basic Sciences , Damghan, Iran
Published online: 16 Aug 2010.
To cite this article: Batool Akhlaghinia (2004) EFFICIENT CONVERSION OF TETRAHYDROPYRANYL (THP) ETHERS TO THEIR
CORRESPONDING CYANIDES WITH TRIPHENYLPHOSPHINE/2,3-DICHLORO- 5,6-DICYANOBENZOQUINONE/n-Bu4 NCN, Phosphorus,
Sulfur, and Silicon and the Related Elements, 179:9, 1783-1786, DOI: 10.1080/10426500490466463
To link to this article: http://dx.doi.org/10.1080/10426500490466463
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Phosphorus, Sulfur, and Silicon, 179:1783–1786, 2004
ꢀC
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490466463
EFFICIENT CONVERSION
OF TETRAHYDROPYRANYL (THP) ETHERS
TO THEIR CORRESPONDING CYANIDES
WITH TRIPHENYLPHOSPHINE/2,3-DICHLORO-
5,6-DICYANOBENZOQUINONE/n-Bu4 NCN
Batool Akhlaghinia
Department of Chemistry, Damghan University of
Basic Sciences, Damghan, Iran
(Received December 9, 2003; accepted January 8, 2004)
Tetrahydropyranyl ethers were converted to their corresponding alkyl
cyanides efficiently by using the triphenylphosphine/ 2,3-dichloro-5,6-
dicyanobenoquinone/n-Bu4 NCN system in refluxing acetonitrile with
good-to-excellent yields.
Keywords: 2,3-Dichloro-5,6-dicyanobenzoquinone(DDQ); alkyl
cyanide; cyanation; tetrahydrophenyl ether (ROTHP); triphenylphos-
phine (TPP)
INTRODUCTION
The nitrile functional group is widely used as a useful intermediate in
organic transformations.1,2 A variety of synthetic methods for the intro-
duction of a cyano group to organic compounds has been documented.3
A general procedure for the preparation of nitriles involves the nucle-
ophilic substitution of a leaving group with a metal cyanide.4 Organic
halogen compounds, aryl sulfonates, alcohols, esters, ethers, nitro or
amino compounds, and diazonium salts could be used as substrates
suitable for this type of reaction. In most cases the substitution reac-
tion follows an SN2 mechanism.
Tetrahydropyranylation (THP) is one of the most practical and pop-
ular ways of protecting hydroxyl groups of alcohols and phenols, espe-
cially in the synthesis of multifunctional organic molecules. THP ethers
The author acknowledges the partial support of this study by the Damghan University
Research Council.
Address correspondence to Batool Akhlaghinia, Department of Chemistry, Damghan
University of Basic Sciences, Damghan, Iran. E-mail: b-akhlaghinia@dubs.ac.ir
1783

1784
B. Akhlaghinia
show remarkable stability toward some reagents such as organometal-
lic reagents, hydrides, and reducing and oxidizing agents. Chemi-
cal transformation of protected functional groups to other functional
groups is an important step in organic synthesis.5 Aliterature search
reveals that only few reports are available for direct conversion of THP
ethers to other functional groups. The examples are conversion of THP
ethers to bromides,6,7 iodides,8 sulfides,9 acetates,10 and esters.11
In this study, a novel and simple method for efficient conversion of
tetrahydropyranyl ethers to alkyl cyanides is reported.
RESULTS AND DISCUSSION
Recently, Iranpoor et al.12 have reported the application of Ph3P/
DDQ/R4NX (X = Cl, Br, I, CN) for conversion of alcohols, thiols, and
selenols into their corresponding alkyl halide and cyanides. Due to the
wide applicability of tetrahydropyranyl ethers in multistep synthesis,
we decided to study the use of a similar system for the transformation
of this functional group to the nitrile group.
In this research, the conversion of tetrahydropyranyl ethers to the
corresponding alkyl cyanides by using Ph3P/DDQ/n-Bu4NCN system
was investigated. This method is very efficient and performs under neu-
tral and very mild reaction conditions (Scheme 1).
Ph3P/DDQ/n-Bu4NCN
ROTHP
−→ RCN
CH3CN, reflux
R = primary, secondary and tertiary alkyl
SCHEME 1
In order to optimize the reaction conditions, at first the effect of different
ratios of ROTHP/PPh3/DDQ/n-Bu4NCN, solvent, and temperature for
conversion of PhCH2OTHP to PhCH2CN were examined. Employing
the ratio of 1/2/2/2 in CH3CN at reflux gave the best result and produced
benzyl cyanide after 4 h in 96% yield. We then applied these optimized
conditions for conversion of structurally different tetrahydropyranyl
ethers into their corresponding alkyl cyanides. The results are shown
in Table I.
As shown in Table I, this method is very suitable for the conversion
of primary, secondary, and tertiary tetrahydropyranyl ethers to alkyl
cyanides in excellent yields.

Cyanation
1785
TABLE I Conversion of Tetrahydropyranyl Ethers into
Alkyl Cyanides in Dry Acetonitrile Under Reflux Condition
Time Conversion
(h)
Isolated
yield (%)
Entry
ROTHP
(%)a
1
2
4
5
100
100
95
97
3
7
100
90
4
5
6
7
8
24
4
100
100
100
100
100
90
94
93
96
95
4
4
3
9
4.5
100
100
95
94
10
6
11
6.5
100
90
aGC yield using internal standard.
In conclusion, the present investigation has demonstrated that the
use of Ph3P/DDQ/n-Bu4NCN offers a simple, novel, and convenient
method for the conversion of a wide varieties of tetrahydropyranyl
ethers to their corresponding alkyl cyanides.
EXPERIMENTAL
Chemicals were obtained from Merck and Fluka chemical compa-
nies. Fourier transform infrared (FTIR) spectra were recorded on a
Perkin Elmer RXI spectrometer. All tetrahydropyranyl ethers were

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B. Akhlaghinia
synthesized as described in the literature.13 The products were puri-
fied by column chromatography, and the purity determination of the
products was accomplished by GLC on a Shimadzu model GC 10-A
instrument using n-octane as internal standard or by thin layer chro-
matography on silica gel polygram on SIL G/UV 254 plates. NMR spec-
tra were recorded on a Bruker Advance DPX 250 MHz instrument.
Typical Procedure for Conversion of Benzyl
Tetrahydropyranyl Ether to Benzyl Cyanide
To a flask containing a mixture of DDQ (2 mmol, 0.454 g) and Ph3P
(2 mmol, 0.524 g) in dry CH3CN (5 ml), while stirring Bu4NCN (2 mmol,
0.537 g) was added. Benzyl tetrahydropyranyl ether (1 mmol, 0.192 g)
was then added to this mixture. The reaction mixture was refluxed. GC
analysis showed that the reaction was completed after 4 h. The solvent
was evaporated under reduced pressure. Column chromatography of
the crude product on silica gel using n-hexane as eluent gave benzyl
cyanide in 96% yield. The product was identified by comparison of its
physical constants and spectral data with those of an authentic sample.
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