Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Patent
1998-06-01
2000-05-16
Shah, Mukund J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
C07D22314
Patent
active
060639202
DESCRIPTION:
BRIEF SUMMARY
This invention relates to novel compounds and the use of such compounds as catalysts in oxygen transfer reactions.
The catalytic asymmetric epoxidation of alkenes using chiral catalysts, in particular the salen manganese complexes of Jacobsen et al (International Patent Application, Publication Number WO/91/14694), is now well established methodology in asymmetric synthesis. The importance of these catalytic systems stems in the main from the versatility of application of the asymmetric epoxidation reaction itself. This versatility is due to the many and varied nucleophiles which can be used to open the substrate epoxide providing a concomitantly varied range of enantiomerically enriched products which are increasingly required for use for the manufacture of biologically important compounds such as pesticides, herbicides and pharmaceuticals.
In addition to organo-transition metal based catalysts, such as the Jacobsen catalysts purely organic asymmetric catalysts are also known. Thus Hanquet et al (Tetrahedron Letters, Vol. 34, no.45, pp7271-7274) have demonstrated that the oxaziridinium salt (1S, 2R, 3R, 4S)-N-methyl-1,2-oxido-3-methyl-4-phenyl-1,2,3,4-tetrahyroisoquinolinium tetrafluoroborate catalyses the asymmetric epoxidation of trans-stilbene and the asymmetric oxidation of methyl p-tolyl sulphide to the corresponding sulphoxide. The oxaziridinium salts are prepared in situ from a catalytic amount of an iminium salt and oxone (Hanquet et al C.R.Acad Sci., Paris, 1991, 313,SII, pp625-628).
Unlike the salen manganese complexes and other organo-transition metal based catalysts, the oxaziridinium catalysts do not function by means of radical intermediates. They may therefore be used with a wider range of alkene substrates as there is no requirement for .pi.-stabilising groups on the alkene (to stabilise incipient radicals). Also, the oxidation reactions of the oxaziridinium catalysts are stereospecific in the sense that cis alkenes give cis epoxides and trans alkenes give trans epoxides. To data however, despite these advantages, the oxaziridinium catalysts have not provided oxidation systems for use on an industrial scale.
It has now been discovered that a novel series of oxaziridium salts show much promise in the catalytic asymmetric epoxidation of alkenes. The catalytic reaction employed is simple and robust enabling the use of readily available and cheap reagents as well as environmentally safe solvents.
Accordingly, in a first aspect, the invention provides a compound of formula (Ia) or (Ib): ##STR2## wherein A and B each independently represents hydrogen or one, two or three naphthylidene substituents, which substituents are selected from C.sub.1-6 alkyl, C.sub.1-6 alkoxy, aryl, aryloxy, silyl and silyloxy; moiety of formula (a): ##STR3## wherein R.sup.2 represents C.sub.1-6 alkyl, phenyl or benzyl, R.sup.3 represents H or OR.sup.4 an integer 1 or 2; and
Suitably, A represents hydrogen.
Suitably, B represents hydrogen.
Examples of R.sup.1 when it represents C.sub.1-6 alkyl are methyl and ethyl groups.
An example of R.sub.1 benzyl.
Suitably, R.sup.2 represents C.sub.1-6 alkyl.
Suitably, R.sup.3 represents C.sub.1-6 alkyl.
Preferably, R.sup.1 represents C.sub.1-6 alkyl,
Values for the counter ion X.sup.- include BF.sub.4 .sup.-, Cl.sup.-, Br.sup.-, I.sup.-, ClO.sub.4.sup.- and PF.sub.6.sup.-.
A preferred value for the counter ion X.sup.- is BF.sub.4.sup.-.
A suitable aryl group is a phenyl group.
As used herein, alkyl groups, whether presents alone or as part of other groups such as alkoxy or aralkyl groups, are alkyl groups having straight or branched carbon chains, containing 1 or 6 carbon atoms, e.g. methyl, ethyl, n-propyl, iso-propyl, n-butyl, isobutyl or tert-butyl groups.
The compounds of formula (Ia) or (Ib) may be prepared by reacting, as appropriate, a compound of formula (IIa) or (IIb): ##STR4## wherein A and B are as defined in relation to formula (I), with an alkylating agent of formula (III): leaving group or atom; and thereafter salting the compound produced with a source of counter ion
REFERENCES:
patent: 5360568 (1994-11-01), Madison et al.
Bohe et al., The Stereospecific Synthesis of a New Chiral Oxaziridinium Salt, Tetrahedron Letters, vol. 34, No. 45, pp. 7271-7274, 1993.
Mazaleyrat, Methode Simple De Synthese D'Agents De Transfert Chiraux Par Action D'un Agent Alkylant a Squelette Binaphtyle-1,1', Tetrahedron Letters, vol. 24, No. 12, pp. 1243-1246, 1993.
Aggarwal et al., Catalytic Asymmetric Synthesis of Epoxides Mediated by Chiral Iminium Salts, Chemical Communications, No. 2, pp. 191-192, Jan. 1996.
Coleman Brenda
Kanagy James M.
Kinzig Charles M.
Shah Mukund J.
University of Sheffield, Western Bank
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