Directed Lithiation of N-Benzenesulfonyl-3-bromopyrrole. Electrophile-Controlled Regioselective Functionalization via Dynamic Equilibrium between C-2 and C-5 Lithio Species
摘要:
Directed lithiation of N-benzenesulfonyl-3-bromopyrrole (1) with LDA in THF at -78 degrees C generated C-2 lithio species 3 selectively. Reactions of 3 with reactive electrophiles produced the corresponding 2-functionalized pyrroles 4. On the other hand, quenching with less reactive electrophiles generated the corresponding 5-substituted pyrroles 5. The latter unusual functionalization at C-5 could be rationalized by dynamic equilibrium between C-2 and C-5 lithio species,
Regiocontrolled halogen dance of 2,5-dibromopyrroles using equilibrium between dibromopyrrolyllithiums
作者:Tatsuki Okumi、Atsunori Mori、Kentaro Okano
DOI:10.1039/d2cc06373e
日期:——
A regiocontrolled halogendance reaction of 2,5-dibromopyrroles is described. An N,N-dimethylsulfamoyl group on the pyrrole nitrogen was especially effective for facilitating interconversion of the resulting 2,3- and 2,4-dibromopyrrolyllithiums, rendering the smooth halogendance reaction. This method was applicable to the formal synthesis of atorvastatin.