Oxo clusters of early transition metals in their highest oxidation state, polyoxometalates or POMs, are receiving much attention because of the great versatility of their molecular structures and properties. Among their numerous applications,1 catalysis surely occupies a prominent place2 and many papers have been published on the use of POMs as oxidation catalysts. However, transfer reactions of other groups like carbene catalysed by polyoxometalates3 are almost absent from the POMs literature. This drove our impetus to explore this still fallow domain, in line with the request for new sustainable methodologies to synthesise fine chemicals. Carbene transfer reactions to olefins yield cyclopropanes, an important class of building blocks in organic synthesis due to the high reactivity of the three membered ring. The scientific community currently devotes great effort in developing efficient and selective methodologies to afford cyclopropanes, because the extreme versatility of ring-opening and ring-expansion reactions allows the synthesis of biological and pharmaceutical species.4 Metalloporphyrin complexes are well known for catalysing cyclopropanations using diazoderivatives as carbene sources,5 but a practical application of porphyrin-based homogeneous catalytic cyclopropanations is hampered by the difficulty to recover and recycle the catalyst, an essential condition for an eco-compatible synthetic strategy. POMs are often presented as inorganic porphyrin-like species, therefore we decided to investigate their catalytic activity in cyclopropanations and our recent results are herewith reported. A wide class of cyclopropanes were obtained in yield up to 98% employing copper substituted polyoxometalates as catalysts and a mol ratio catalyst/EDA/olefin = 1:100.000:100.000. The use of an equi-molar ratio EDA/olefin and the formation of molecular nitrogen as a by-product confer to this methodology a very high atom-efficiency. Besides, the impressive TON observed circumvents problems connected to the catalyst recovery and it is promising for industrial applications of POMs as cyclopropanation catalysts. References: 1. Long, D.-L; Tsunashima, R.; Cronin, L. Angew. Chem. Int. Ed. 2010, 49, 1736. 2. Hill, C. L; Comprehensive Coord. Chem. II, J. A. McCleverty, T. J. Meyer, Eds, 2003. 3. a) Wei, Z. Y.; Dickman, M. H.; Pope, M. T. Inorg Chem, 1997, 36, 130. b) Yadav, J. S.; Reddy, B. S.; Purnima, K.; Nagaiah, K.; Lingaiah, N. J. Mol. Catal.: A, 2008, 285, 36. 4. Carson, C. A.; Kerr, M. A. Chem. Soc. Rev. 2009, 38, 3061. 5. a) Deng, Q.-H.; Chen, J.; Huang, J.-S.; Chui, S. S.-Y.; Zhu, N.; Li, G.-Y.; Che, C.-M. Chem. Eur. J. 2009, 15, 10707; b) Fantauzzi, S.; Gallo, E.; Rose, E.; Raoul, N.; Caselli, A.; Issa, S.; Ragaini, F. Cenini, S. Organometallics 2008, 27, 6143.

Polioxometalates : powerful catalysts for atom-efficient cyclopropanations / I. Boldini, A. Caselli, E. Gallo, G. Guillemot, A. Proust. ((Intervento presentato al 9. convegno Congresso del Gruppo Interdivisionale di Chimica Organometallica tenutosi a Firenze nel 2010.

Polioxometalates : powerful catalysts for atom-efficient cyclopropanations

A. Caselli
Secondo
;
E. Gallo;
2010

Abstract

Oxo clusters of early transition metals in their highest oxidation state, polyoxometalates or POMs, are receiving much attention because of the great versatility of their molecular structures and properties. Among their numerous applications,1 catalysis surely occupies a prominent place2 and many papers have been published on the use of POMs as oxidation catalysts. However, transfer reactions of other groups like carbene catalysed by polyoxometalates3 are almost absent from the POMs literature. This drove our impetus to explore this still fallow domain, in line with the request for new sustainable methodologies to synthesise fine chemicals. Carbene transfer reactions to olefins yield cyclopropanes, an important class of building blocks in organic synthesis due to the high reactivity of the three membered ring. The scientific community currently devotes great effort in developing efficient and selective methodologies to afford cyclopropanes, because the extreme versatility of ring-opening and ring-expansion reactions allows the synthesis of biological and pharmaceutical species.4 Metalloporphyrin complexes are well known for catalysing cyclopropanations using diazoderivatives as carbene sources,5 but a practical application of porphyrin-based homogeneous catalytic cyclopropanations is hampered by the difficulty to recover and recycle the catalyst, an essential condition for an eco-compatible synthetic strategy. POMs are often presented as inorganic porphyrin-like species, therefore we decided to investigate their catalytic activity in cyclopropanations and our recent results are herewith reported. A wide class of cyclopropanes were obtained in yield up to 98% employing copper substituted polyoxometalates as catalysts and a mol ratio catalyst/EDA/olefin = 1:100.000:100.000. The use of an equi-molar ratio EDA/olefin and the formation of molecular nitrogen as a by-product confer to this methodology a very high atom-efficiency. Besides, the impressive TON observed circumvents problems connected to the catalyst recovery and it is promising for industrial applications of POMs as cyclopropanation catalysts. References: 1. Long, D.-L; Tsunashima, R.; Cronin, L. Angew. Chem. Int. Ed. 2010, 49, 1736. 2. Hill, C. L; Comprehensive Coord. Chem. II, J. A. McCleverty, T. J. Meyer, Eds, 2003. 3. a) Wei, Z. Y.; Dickman, M. H.; Pope, M. T. Inorg Chem, 1997, 36, 130. b) Yadav, J. S.; Reddy, B. S.; Purnima, K.; Nagaiah, K.; Lingaiah, N. J. Mol. Catal.: A, 2008, 285, 36. 4. Carson, C. A.; Kerr, M. A. Chem. Soc. Rev. 2009, 38, 3061. 5. a) Deng, Q.-H.; Chen, J.; Huang, J.-S.; Chui, S. S.-Y.; Zhu, N.; Li, G.-Y.; Che, C.-M. Chem. Eur. J. 2009, 15, 10707; b) Fantauzzi, S.; Gallo, E.; Rose, E.; Raoul, N.; Caselli, A.; Issa, S.; Ragaini, F. Cenini, S. Organometallics 2008, 27, 6143.
giu-2010
Settore CHIM/03 - Chimica Generale e Inorganica
Società chimica italiana
Polioxometalates : powerful catalysts for atom-efficient cyclopropanations / I. Boldini, A. Caselli, E. Gallo, G. Guillemot, A. Proust. ((Intervento presentato al 9. convegno Congresso del Gruppo Interdivisionale di Chimica Organometallica tenutosi a Firenze nel 2010.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/165871
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