Efficient Oxidative Spirolactamization by μ-Oxo Bridged Heterocyclic Hypervalent Iodine Compound

Iodanes as multi-tools for the total synthesis of complex natural products

“…8 Undoubtedly, Professor Kita's group in Japan has set benchmarks for phenol dearomatizations. 9 They reported the first approach for the formation of C–O bonds, which was later widely extended to various nucleophiles. They have demonstrated that the use of perfluorinated alcohols, 10 such as trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP), are key solvents for such transformations and have enabled the development of valuable new applications.…”

“…As an alternative for the construction of the complex main core of tetrodotoxin, in 2021, Johnson and coworkers 19 proposed an elegant approach based on a Kita oxidative dearomatization process 9 leading to dienone 14 followed by an acyl nitroso Diels–Alder cycloaddition to generate functionalized species 15 with a good diastereoselectivity. Further elaborations enabled the formation of an advanced intermediate of tetrodotoxin 16 , Scheme 4.…”

“…21 The target C–N bond was produced by a Pictet–Spengler cyclization in tandem with a Kita oxidative dearomatization process. 9 First, oxindole 22 was produced through a dearomatization–Michael–rearomatization cascade mediated by PIDA from phenol 21 . Second, treatment of 22 with PIFA and then phosphoric acid led to the formation of the target tetracyclic system 23 .…”

“…27 Unfortunately, the [5+2] cycloaddition failed with electron-poor alkene 42 as the cyclo-adduct. Alternatively, a Kita oxidative dearomatization 9 in tandem with a Diels–Alder reaction mediated by PIDA in methanol led to the polycyclic structure 44 in 70% yield. The ring contraction was promoted with a Beckwith–Dowd rearrangement.…”

“…In 2019, Peixoto, Quideau et al published total syntheses of twelve natural molecules belonging to the Securinega alkaloid family, 37 and all of them were obtained from the key intermediate menisdaurilide 73 . This intermediate was obtained through a multi-step sequence performed in a single day that was based on a Kita oxidative phenol dearomatization 9 in the presence of PIDA, followed by an intramolecular 1,4-oxa-Michael cyclization under acidic conditions, Scheme 18.…”