Recyclable copper(i)-catalyzed cascade C–S and C–N bond formation between 2-iodoanilines and 2-bromobenzenethiols towards functionalized phenothiazines

Abstract

A mesoporous SBA-15-immobilized L-proline-Cu(I) complex [L-proline-CuI-SBA-15] was prepared via immobilization of commercially readily available (4-(chloromethyl)phenyl)trimethoxysilane onto SBA-15, followed by a reaction with N-Boc-trans-4-hydroxy-L-proline, and then deprotection and coordination with CuI. With the use of 30 mol% of L-proline-CuI-SBA-15 as a catalyst, the cascade C–S/C–N coupling reaction between 2-iodoanilines and 2-bromothiophenols proceeded smoothly in 2-methoxyethanol at 90–110 °C with K₂CO₃ as a base to deliver a wide range of substituted phenothiazines in good to high yields with wide tolerance of functional groups. This heterogenized copper(I) catalyst could be easily recovered by centrifugation of the reaction mixture and recycled more than seven cycles without a significant loss of catalytic activity.