Novel applications of N-sulfonyl-alkylamines in [2+4] cycloadditions

Abstract

N-Sulfonylamine 2c was generated from the corresponding sulfamoyl chloride 1c at - 78 °C by triethylamine-induced dehydrohalogenation or from the novel precursor 5 with a phthalimidyl leaving group at room temperature. Trapping of 2c from either source with 3-trimethylsiloxy-1,3-butadiene ( 3) gave the expected [2+4] cycloadduct 4. However, the reaction of N-sulfonyl-alkylamines 2 with 2-aza-1,3-dienes 7 depended on the size of the alkyl group in 2 and on the reaction conditions. Thus, use of the heterocumulenes 2a,b (alkyl residue = Me, Et) at − 78 °C gave rise to the cycloadducts 8a,b regioselectively. In contrast, the reaction of 7 with 2c,d carrying a bulky isopropyl or tert.-butyl group provided the bissulfamoylated 2-aza-1,3-dienes 10a-c. On the other hand, starting from precursor 5 at room temperature also 2c reacted with the dienes 7 to form the ring-closure products 8c,d.