Rh(III)-Catalyzed [4 + 1] Annulation of Sulfoximines with Maleimides: Access to Benzoisothiazole Spiropyrrolidinediones

Abstract

Rh(III)-catalyzed synthesis of benzoisothiazole spiropyrrolidinediones using sulfoximine as a directing group under a C–H activation and [4 + 1] annulation strategy with maleimides as a coupling partner is reported. The cyclization reaction was compatible with various substituted sulfoximine and maleimides. The deuterium-labeling studies were performed to investigate the mechanism of the reaction.

A rhodium-catalyzed cascade C–H activation/annulation strategy for the expeditious assembly of pyrrolidinedione-fused 1,2-benzothiazines

“…The reaction hardly took place in the absence of an additive or oxidant (Table 1, entries 9 and 17). Subsequently, the loading of the catalyst, additive and oxidant was examined, and the reaction did not afford any favorable outcome (Table 1, entries [18][19][20][21][22]. Furthermore, the reaction time and temperature had some effect on the conversion.…”

“…Subsequently, the coordination of maleimide 2a with rhodacycle A formed intermediate B , followed by the migratory insertion of the double bond into the C–Rh bond to generate intermediate C , which would participate in the E 2 -elimination process to yield the corresponding Heck-type intermediate and subsequently afford the spirocyclic product in the presence of an acid additive, as proposed in previous literature. 18,21 In this protocol, intermediate C participated in a reductive elimination process to afford intermediate D by releasing the Rh( i ) species, which was oxidized by a copper salt to form the active Rh( iii )-catalyst to continue the catalytic cycle. Finally, the desired product 3a was formed through oxidative aromatization of intermediate D .…”

“…17 Very recently, Wei established a Rh( iii )-catalyzed C–H activation and [4 + 1] annulation strategy of sulfoximines with maleimides to give benzoisothiazole spiropyrrolidinediones (Scheme 1e). 18 In continuation of our interest in investigating fused heterocyclic systems, 19 we sought to adopt the transition-metal-catalyzed C–H activation and annulation between sulfoximines and maleimides for the modular assembly of pyrrolidinedione-fused 1,2-benzothiazines under mild conditions with good functional group compatibility (Scheme 1f).…”

Recent advances in spirocyclization of maleimides via transition-metal catalyzed C–H activation

“…Liu et al in 2023 reported the spirocyclization of sulfoximines 96 with maleimides 16 in the presence of a Rh-catalyst, AgSbF 6 , copper acetate, acetic acid, and nitrobenzene in trifluoroethanol (TFE) medium (Scheme 21). 23 During the study it was observed that in the absence of nitrobenzene, a low yield of the spirocycle was formed. Thus, nitrobenzene played a role in enhancing the product yield.…”