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![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
An Isolable Base-Stabilized Diazosilenyl Cation
Shintaro Takahashi1, Aurora Rodríguez-Álvarez1, Antoine Baceiredo1
1Université de Toulouse, UPS, and CNRS, LHFA UMR 5069 188 route de Narbonne, 31062, Toulouse, France.
Abstract:
In contrast to the emerging chemistry of stable diazoalkenes, there are not yet any studies devoted to heavier silicon analogues, diazosilenes. Here, we report the synthesis of a base-stabilized diazosilenyl cation 2 by the reaction of base-stabilized C-phosphonio-silyne 1 with N2O. This silicon analog of diazoalkenes 2 exhibits a remarkable stability thanks to the coordination of phosphine and phosphine oxide ligands at the cationic silicon center. In addition, DFT calculations predict that, due to a particular stabilizing effect of the electropositive silicon atom, for diazosilenes (R2Si=C=N2), the presence of π-donor substituents is not essential to prevent N2 dissociation, contrary to carbon analogues. Interestingly, diazosilenyl cation 2 tends to isomerize into (silylene)(phosphonio)diazomethane 7 via a 1,2-phosphine ligand migration and thus exhibits dual reactivity as a diazoalkene and as a diazo-substituted silylene.
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