The unprecedented phospha-aza-Diels-Alder reaction between an activated electron-poor imine and 2H-phospholes yields 1-phospha-2-azanorbornenes in a highly chemoselective and moderately diastereoselective reaction. The intermediate 2H-phospholes, which act as dienes, are formed in situ from the corresponding 1H-phospholes. Theoretical calculations confirm that the phospha-aza-Diels-Alder reaction is of normal electron demand. The reactive P-N bond in 1-phospha-2-azanorbornenes can be cleaved by nucleophiles leading to the formation of 2,3-dihydrophospholes.
Keywords: cycloadditions; imines; nitrogen heterocycles; phospholes; phosphorus heterocycles.
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