Blue LED Irradiation of Iodonium Ylides Gives Diradical Intermediates for Efficient Metal‐free Cyclopropanation with Alkenes

Abstract

Af acile and highly chemoselective synthesis of doubly activated cyclopropanes is reported where mixtures of alkenes and b-dicarbonyl-derived iodonium ylides are irradiated with light from blue LEDs.This metal-free synthesis gives cyclopropanes in yields up to 96 %, is operative with cyclic and acyclic ylides,a nd proceeds with av ariety of electronicallydiverse alkenes.C omputational analysis explains the high selectivity observed, which derives from exclusive HOMO to LUMO excitation, instead of free carbene generation. The procedure is operationally simple,u ses no photocatalyst, and provides access in one step to important building blocks for complex molecule synthesis. Scheme 1. Light-mediated reactions of iodonium ylides.

Synthesis and Properties of ortho-t-BuSO2C6H4-Substituted Iodonium Ylides

“…Based on these observations and recent related reports by other groups [7], the reaction seems to proceed via a T-shaped tri-coordinated intermediate, which is different from Based on these observations and recent related reports by other groups [7], the reaction seems to proceed via a T-shaped tri-coordinated intermediate, which is different from a free carbene species [32]. The T-shaped tricoordinated intermediate could be formed via a biradical species generated via photoirradiation [33]. The unexpected selectivity of the reductive elimination might be explained by the steric hindrance of the dimedone and Meldrum's acid moieties in 2f and 2g, although a detailed mechanism for this transformation, including the selectivity in the case of 2e, is not clear at this stage.…”

All‐Carbon Tetrasubstituted Olefins Synthesis from Diazo Compounds and Iodonium Ylides under Blue LED Irradiation

“…The reactions reported so far mainly relying on the use of high‐energy mercury (Hg) lamps which unavoidable caused the low chemoselectivity, side reactions, or limited substrate scopes. Until 2019, Murphy and co‐workers achieved the irradiating mixtures of iodonium ylides and alkenes with blue LEDs, providing a mild and highly efficient approach for the synthesis of cyclopropanes [9] . Recently, Sen et al .…”

Hypervalent iodine chemistry and light: photochemical reactions involving hypervalent iodine chemistry

“…Recently, a photochemical cyclopropanation of olefins was developed by the reaction with iodonium ylides without using any photoredox catalyst. 101 During these transformations, the reaction mixture of olefins 117 and -dicarbonyl-derived iodonium ylides 124-126 was irradiated with blue light obtained from blue LED and doubly activated cyclopropanes 128 were obtained in good to excellent yields (Scheme 41). The cyclopropanation reaction proceeded well with cyclic and acyclic iodonium ylides and showed versatility with different electronically diverse olefins.…”