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Updated: Jun 28, 2025

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Phenoxaphosphonium Mixed Ylides in Ring Expansion Reaction
Anton S Nenashev1, Dmitrii A Dospekhov1, Mikhail V Zavaruev1
1Department of Chemistry Lomonosov Moscow State University, Building 3, 1 Leninskie Gory, 119334 Moscow, Russian Federation.
Abstract:
Treatment of mixed phosphonium-iodonium ylides featuring a six-membered phenoxaphosphonium fragment with aqueous tetrafluoroboronic acid induces a rearrangement, resulting in expansion of the phosphacycle and oxidation of the phosphorus atom. The target difficult-to-access dibenzo[b,f][1,4]oxaphosphepine oxides (3 examples) were isolated in excellent yields (up to 95%) as mixtures of stereoisomers. Hydrolysis of a five-membered mixed ylide, a dibenzophosphole derivative, predominantly preserves the phosphole system with cycle expansion occurring as a side process.
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