An Efficient Highly Regioselective Synthesis of 2,3,4-Trisubstituted Pyrroles by Cycloaddition of Polarized Ketene <i>S</i>,<i>S-</i> and <i>N</i>,<i>S-</i>Acetals with Activated Methylene Isocyanides^†

An efficient route for regioselective synthesis of 2,3,4- substituted pyrroles allowing precise control over the introduction of a number of substituents and functionalities (tosyl, carbalkoxy, aryl, cyano, nitro, acetyl, benzoyl, cyclic amines, etc.) at the three positions of the pyrrole ring has been developed via 1,3-dipolar cycloaddition of readily accessible polarized ketene S,S- and N,S-acetals with carbanions derived from activated methylene isocyanides.本研究开发出一条区域选择性合成2,3,4-取代吡咯（pyrrole）的高效路径，该路径可精准控制在吡咯环的三个位置引入多种取代基与官能团，包括对甲苯磺酰基、烷氧羰基、芳基、氰基、硝基、乙酰基、苯甲酰基、环胺等；该合成路径通过易得的极化烯酮S,S-缩醛与N,S-缩醛，与活化亚甲基异氰化物衍生的碳负离子之间的1,3-偶极环加成反应实现。