Abstract
Chemoselective deoxygenation of N -oxides was carried out under mild conditions with common phosphines in the presence
of dichlorodioxomolybdenum(VI).
Key words
N -oxides - azoxy compounds - molybdenum(VI) - nitrones - oxotransfer catalysis
References
<A NAME="RD02405ST-1A">1a </A>
Ochiai E. In
Aromatic Amine Oxides
Elsevier;
Amsterdam:
1967.
p.184
<A NAME="RD02405ST-1B">1b </A>
Gilchrist TL. In Comprehensive Organic Synthesis
Vol. 8:
Trost BM.
Fleming I.
Pergamon;
Oxford:
1991.
p.390
<A NAME="RD02405ST-2A">2a </A>
Emerson TR.
Ress CW.
J. Chem. Soc.
1962,
1917
<A NAME="RD02405ST-2B">2b </A>
Howard E.
Olszewski WF.
J. Am. Chem. Soc.
1959,
81:
1483
<A NAME="RD02405ST-3">3 </A>
Katritzky AR.
Monro AM.
J. Chem. Soc.
1958,
1263
<A NAME="RD02405ST-4">4 </A>
Essery JM.
Schofield K.
J. Chem. Soc.
1960,
4953
<A NAME="RD02405ST-5">5 </A>
Aoyagi Y.
Abe T.
Ohta A.
Synthesis
1997,
891
<A NAME="RD02405ST-6">6 </A>
Brown HC.
Subba Rao BC.
J. Am. Chem. Soc.
1956,
78:
2582
<A NAME="RD02405ST-7">7 </A>
Balicki R.
Synthesis
1989,
645
<A NAME="RD02405ST-8">8 </A>
McCall JM.
Tenbrink RE.
Synthesis
1975,
335
<A NAME="RD02405ST-9">9 </A>
Konwar D.
Boruah RC.
Sandhu JS.
Synthesis
1990,
337
For recent reports, see for instance:
<A NAME="RD02405ST-10A">10a </A>
Yadav JS.
Reddy BVS.
Reddy MM.
Tetrahedron Lett.
2000,
41:
2663
<A NAME="RD02405ST-10B">10b </A>
Nicolaou KC.
Koumbis AE.
Snyder SA.
Simonsen KB.
Angew. Chem. Int. Ed.
2000,
39:
2529
<A NAME="RD02405ST-10C">10c </A>
Chandrashekar S.
Reddy CR.
Rao RJ.
Rao JM.
Synlett
2002,
349
<A NAME="RD02405ST-11">11 </A>
PPh3 only deoxygenates pyridine N -oxides at temperatures over 250 °C.
[2b ]
<A NAME="RD02405ST-12">12 </A>
Wang Y.
Espenson JH.
Org. Lett.
2000,
2:
3525
<A NAME="RD02405ST-13A">13a </A>
Arnáiz FJ.
Aguado R.
Pedrosa MR.
de Cian R.
Fischer J.
Polyhedron
2000,
19:
2141
<A NAME="RD02405ST-13B">13b </A>
Arnáiz FJ.
Aguado R.
Pedrosa MR.
Mahía J.
Maestro MA.
Polyhedron
2001,
20:
2781
<A NAME="RD02405ST-13C">13c </A>
Arnáiz FJ.
Aguado R.
Pedrosa MR.
de Cian R.
Inorg. Chim. Acta
2003,
347:
33
<A NAME="RD02405ST-14">14 </A>
Sanz R.
Aguado R.
Pedrosa MR.
Arnáiz FJ.
Synthesis
2002,
856
<A NAME="RD02405ST-15">15 </A>
Sanz R.
Escribano J.
Aguado R.
Pedrosa MR.
Arnáiz FJ.
Synthesis
2004,
1629
<A NAME="RD02405ST-16">16 </A> Aromatic N -oxides were commercially available or prepared by treatment of the corresponding
pyridine with H2 O2 -AcOH:
Taylor EC.
Crovetti AJ.
Org. Synth. Coll. Vol. IV
Wiley;
New York:
1963.
p.654
<A NAME="RD02405ST-17">17 </A> Nitrones 3 were prepared according to:
Mitsui H.
Zenki S.
Shiota T.
Murahashi S.
J. Chem. Soc., Chem. Commun.
1984,
874
<A NAME="RD02405ST-18">18 </A>
We have found that in general alkylamines react with dioxomolybdenum chlorides leading
to decomposition products some of them have been characterized as alkylammonium polymolybdates:
Arnáiz, F. J.; Pedrosa, M. R.; Aguado, R. unpublished results.
<A NAME="RD02405ST-19">19 </A>
The complete reduction of 5 required about 15 h.
See for instance:
<A NAME="RD02405ST-20A">20a </A>
Holm RH.
Chem. Rev.
1987,
87:
1401
<A NAME="RD02405ST-20B">20b </A>
Holm RH.
Chem. Rev.
1990,
100:
183
<A NAME="RD02405ST-21">21 </A>
Butcher RJ.
Gunz HP.
Maclagan RGAR.
Kipton H.
Powell J.
Wilkins CJ.
Hian YS.
J. Chem. Soc., Dalton Trans.
1975,
1223