Rhodium(iii)-catalyzed intermolecular [3+3] annulation of benzoxazines with quinone compounds: access to spiro-heterocyclic scaffolds

Abstract

A rhodium(III)-catalyzed redox-neutral spiroannulation approach to access spiro[benzo[b][1,4]oxazine-benzo[c]chromene skeleton is described in this contribution. A variety of spiro[5.5]-heterocyclic scaffolds were obtained in moderate to excellent yields under mild conditions. Key...

C–H activation-initiated spiroannulation reactions and their applications in the synthesis of spirocyclic compounds

“…In addition, Yang's group developed a Rh( iii )-catalyzed [3 + 3] spiroannulation of benzoxazines with quinones to afford spiro[benzo[ b ][1,4]oxazine-benzo[ c ]chromene] skeletons (Scheme 51). 44 Moreover, a Ru( ii )-catalyzed spiroannulation between 3-aryl-2 H -benzoxazinones and benzoquinones to yield spiropyrans was reported by Yang et al (Scheme 52). 45…”

Annulations involving p-benzoquinones: stereoselective synthesis of fused, spiro and bridged molecules

“…95 Spirochromenes are frequently found in natural products and employed as useful synthons in synthetic organic chemistry. 97 98 In this transformation, the benzoquinone moiety served as an effective C3-synthon. The plausible mechanism is shown in Scheme 32.…”

“…97 In 2023, Yang et al devised the Rh( iii )-catalyzed [3+3] annulation of benzoxazine 109 and benzoquinone 108 to afford spirobenzo[ b ][1,4]oxazine-benzo[ c ]chromenes 110 under ambient conditions. 98 In this transformation, the benzoquinone moiety served as an effective C3-synthon. The plausible mechanism is shown in Scheme 32.…”

Three-Component Reaction for the Synthesis of Spiro-Heterocycles from Isatins, Substituted Ureas, and Cyclic Ketones

“…The spiroheterocycles are discovered in many natural alkaloids and pharmaceutical molecules with a broad range of biological activities . Consequently, tremendous efforts have been devoted to develop the exploration of the novel and efficient synthetic methods for the construction of structurally diversified spirocyclic compounds . Through an investigation of the literature, it can be found that isatins are one of the most ideal reagents for the synthesis of spirocyclic compounds because 3-carbonyl of them has high reactivity.…”