Functionalized Cyclopentenes via the Formal [4+1] Cycloaddition of Photogenerated Siloxycarbenes from Acyl Silanes

Abstract

This work describes the first formal cycloaddition reaction of photogenerated nucleophilic carbenes derived from acylsilanes with electrophilic dienes. The resulting transient donor−acceptor cyclopropane rearranges to its stable and highly functionalized cyclopentene isomer in an unprecedented metal-free process. The cyclopropanation−vinyl cyclopropane rearrangement sequence was corroborated by computational calculations. The cyclopropane formation corresponds to a higher energetic barrier, and the vinylcyclopropane−cyclopentene rearrangement proceeds through different mechanisms, although of comparable energies, depending on the stereochemistry of the cyclopropane.

Recent progress and perspectives in photo-induced organic reactions of acylsilanes

“…Although the use of acylsilane-derived siloxycarbenes would provide access to highly substituted cyclopropanes, this variation remains challenging due to the presence of electron-withdrawing groups in the olefins as they facilitate the ring-opening of the resulting silyl ether cyclopropanes. 39 This was conceptualized in the synthesis of cyclopentenes 53 via cyclopropane intermediates I accomplished by tuning the electronic nature of the diene 52 (Scheme 21). In this study, the blue-light-induced cyclopropanation-vinyl cyclopropane rearrangement sequence, p -tolyltrimethylsilane and dienes in the presence of molecular sieves, provided cyclopropanes in 66% yield, which was increased to 74% using a TBS group.…”

Visible Light‐Mediated Cyclopropanation: Recent Progress

“…Candeias and Afonso et al . reported a similar reaction to the formation of cyclopentenes by using the formed transient donor−acceptor cyclopropane as the key intermediate [38] …”

“…Under the irradiation with blue LED, an intramolecular cyclopropanation successfully occurred to give a series of cyclopropyl-fused heterocyclic scaffolds, including azabicyclo[3. reported a similar reaction to the formation of cyclopentenes by using the formed transient donor À acceptor cyclopropane as the key intermediate. [38]…”

Visible photons as ideal reagents for the activation of coloured organic compounds

“…259 Carbene addition onto electron-poor dienes such as dicyano-2-methylenebut-3-enoates induced a cyclopropanation-vinyl cyclopropane rearrangement sequence, yielding decorated cyclopentenes via a formal [4+1] cycloaddition. 260 Another interesting application of photogenerated carbenes is the preparation of olefins. A possible strategy is illustrated in Scheme 77a.…”