Potassium exchanged zirconium hydrogen phosphate as heterogeneous catalyst in cyanosilylation of carbonyl compounds

Article abstract of DOI:10.1055/s-1999-2597

Layered zirconium hydrogen phosphate exchanged with potassium ion was found to be an efficient heterogeneous catalyst for cyanosilylation of carbonyl compounds.

Full text of DOI:10.1055/s-1999-2597

LETTER
315
Potassium Exchanged Zirconium Hydrogen Phosphate as Heterogeneous
Catalyst in Cyanosilylation of Carbonyl Compounds
Massimo Curini*, Francesco Epifano, Maria Carla Marcotullio, Ornelio Rosati, Monia Rossi
Istituto di Chimica Organica, Facoltà di Farmacia, Università di Perugia, Via del Liceo, I-06123 Perugia, Italy
FAX: +39-75-5855116; E-mail: Curini@unipg.it
Received 16 November 1999
Abstract: Layered zirconium hydrogen phosphate exchanged with
potassium ion was found to be an efficient heterogeneous catalyst
for cyanosilylation of carbonyl compounds.
Key words: zirconium hydrogen phosphate, heterogeneous cataly-
sis, cyanosilylation, carbonyl compound, cyanohydrins
It is now well established that many acidic and basic sol-
The reaction shows selectivity (entry 14) toward aliphatic
ids act as catalysts in liquid phase organic synthesis.1 We
have recently discovered that layered potassium ex-
changed zirconium hydrogen phosphate Zr(KPO4)2 is an
excellent heterogeneous basic catalyst for aldol-type reac-
tion.2,3 It seemed of interest to test the catalyst for cyano-
silylation of carbonyl compounds in order to obtain cy-
anohydrins as well as their trimethylsilyl ethers which are
important building blocks in organic synthesis.4 Usually
cyanosilylation of carbonyl compounds proceeds using
trimethylsilyl cyanide (TMSCN) in the presence of a
Lewis acid or base.5 Very recently, it was reported that
lanthanide triflate6,7 is also effective in this type of reac-
tions. Only a few examples of heterogeneous catalysis
have been reported using Montmorillonite K-10,8
Clayfen9 as acidic catalysts or HAp, CaO and MgO10 as
basic catalysts.
ketones compared to a,b-unsaturated ketones (e.g. 1→2).
The mechanism of the reaction probably involves the ac-
tivation of TMSCN by its coordination with the basic sites
of the catalyst and subsequent release of nucleophilic cy-
anide ion.10,13 In summary, Zr(KPO4)2 was found to be an
excellent heterogeneous catalyst for cyanosilylation of
carbonyl compounds under mild conditions. The use of
Zr(KPO4)2 is equally effective or better than any reagent
yet reported. The important features of this methodology
are: general application, mild reaction conditions, simple
work-up and recyclable catalyst, whose preparation does
not require any particular skill. Therefore, the present cat-
alytic method should be useful in synthetic organic chem-
istry.
In this comunication we present a convenient method for
the synthesis of cyanohydrin-trimethylsilyl ethers using
Zr(KPO4)2 as heterogeneous catalyst.
The cyano-trimethylsilylation reactions (Scheme 1) were
carried out by adding TMSCN to a mixture of carbonyl
compound and catalyst in dichloromethane at reflux.11
Scheme 1
The reaction takes from 10 minutes to 24 hours (see Ta-
ble) and after a simple work-up affords cyanohydrintri-
methylsilyl ether in excellent yields.12 Aliphatic, aromatic
as well as a,b-unsaturated aldehydes and ketones react
with TMSCN in a very short time in good yields. It is im-
portant to note that, in the case of a,b-unsaturated ketones
(entry 13), the reaction occurs without formation of 1,4
adduct.10
Synlett 1999, No. 3, 315–316 ISSN 0936-5214 © Thieme Stuttgart · New York

316
M. Curini et al.
LETTER
(6) Yang, Y.; Wang, D. Synlett 1997, 1379.
(7) Sanavan, P. R.; Vijaya, A.; Vinod, K. S. Tetrahedron Lett.
1998, 39, 3823.
(8) Somanathan, R.; Rivero, I. A.; Gama, A.; Ochoa, A.; Aguirre,
G. Synth. Commun. 1998, 28, 2043.
Acknowledgement
The authors wish to thank MURST “Progetto Chimica dei Compo-
sti Organici di interesse biologico” and CNR (Roma) for financial
support, and Prof. U. Costantino for helpful discussions.
(9) Onaka, M.; Higuchi, K.; Sugita, K.; Izumi, Y. Chem. Lett.
1989, 1393.
(10) Higuchi, K.; Onaka, M.; Izumi, Y. Bull. Chem. Soc. Jpn. 1993,
66, 2016.
References and Notes
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(11) General procedure. To a stirred mixture of carbonyl com-
pound (2 mmol) and catalyst2 (200 mg) in dichloromethane (2
ml) at reflux was added TMSCN (3 mmol) and the progress of
the reaction monitored by GC-MS. The reaction mixture was
then filtered and the residue washed with dichloromethane.
The organic layer was washed with a saturated solution of
Na2CO3, dried over Na2SO4 and evaporated. The residue was
purified by flash chromatography on SiO2 (eluent CH2Cl2) af-
fording the corresponding trimethylsilyl cyanohydrin.
(12) When the residue of the reaction (see ref. 11) was treated with
HCl 1 N (2 ml) in acetonitrile (2 ml) at 0 °C for a few minutes
after usual work-up the trimethylsilyl ether was quantitatively
converted into corresponding cyanohydrins (see Scheme 1).
(13) Izumi, Y.; Namami, H.; Higuchi, K.; Onaka, M. Tetrahedron
Lett. 1991, 32, 4741.
Synlett 1999, No. 3, 315–316 ISSN 0936-5214 © Thieme Stuttgart · New York