Intramolecular [2+2] photocycloadditions as an approach towards the bicyclo[2.1.1]hexane substructure of solanoeclepin A

Synthesis of the Right-Hand Substructure of Solanoeclepin A

“…complete conversion of the starting material was observed after 2 h ( 1 H NMR) and the expected crossed adduct 12 was formed (Scheme 4). This mode of closure was also observed with the analogous 6-methyldioxenones [3] and is in accordance with the so-called empirical rule of five. [9] This cycloadduct appeared to be unstable, decomposing slowly under the reaction conditions and during the subsequent workup.…”

“…However, we have shown that more highly functionalised tethered alkenes, which will eventually be used in the total synthesis of solanoeclepin A, usually give photoadducts in good yields. [3] The obtained diol 6 was disilylated by treatment with TESCl to afford 13. The primary silyl ether was then oxidised selectively under Swern conditions to afford the aldehyde 14.…”

“…Scheme 1. Retrosynthetic approach During our research effort towards the construction of this challenging target, [3] we have recently described the successful diastereoselective formation of the highly substituted cyclobutane ring 2. [3a,3c] The key step of this synthesis was based on a [2ϩ2] photocycloaddition reaction of the lactone dioxenone precursor 4, followed by the reduction of the obtained adduct (3 Ǟ 2).…”

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

“…The chromophore was also attached as 1,3-dioxin-4-one to the other end of the 2(5 H )-furanone unit. 564 In other approaches the 1,3-dioxin-4-one was employed as the only chromophor. 656 In a methodology-oriented study, it was found 566 that the crossed photocycloaddition product is not always preferred when a C 2 -fragment was employed as a linker.…”

Photochemistry of Cyclobutanes: Synthesis and Reactivity

“…The scope of the intramolecular (2 + 2)-photoadditions within the derivatives of dioxenones has been assessed 223,224 . The irradiation at 300 nm of 355 in acetonitrile/acetone (9:1) affords the cycloadduct 356 as a 1:1 mixture of diastereoisomers.…”