[4 + 2] cycloadditions of nitroalkenes in water. Highly asymmetric synthesis of functionalized nitronates.
The [4 + 2] cycloadditions of (E)-2-aryl-1-cyano-1-nitroalkenes 1 with achiral and enantiopure vinyl ethers 2 and 3 carried out in sole water are reported. These reactions occur in a heterogeneous phase under mild conditions and are fast and highly stereoselective. By using (-)-N,N-dicyclohexyl-(1S)-isoborneol-10-sulfonamide as a chiral auxiliary, the cycloadditions are totally asymmetric. The face selectivity is discussed in terms of the shape of the chiral auxiliary and the reactive conformation of vinyl ether.
Fringuelli
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Dipartimento di Chimica, Università di Perugia, Via Elce di Sotto, 8 I-06123 Perugia, Italy. frifra@unipg.it
Matteucci
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M
Piermatti
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O
Pizzo
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F
Burla
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MC