The use of temporary tethers in the meta photocycloaddition reaction

Chromatography with silver nitrate: part 2

“…SNIS was used in the preparation of two of the geometrical isomers 89 and 90, both derived from the same starting material (91), at the penultimate step prior to PDC oxidation (Scheme 12). Similar target compounds were synthesized to confirm the structure of the cranberry fruitworm (Acrobasis vaccinni Riley) attractant, where SNIS was again required for advanced intermediate purification.…”

“…Penkett et al 91 evaluated the potential of a range of temporary tethers (e.g. 197) linking the phenol and allyl alcohol components (e.g.…”

The Double [3+2] Photocycloaddition Reaction

“…41 The idea of using a temporary, easily removable tether was originally proposed by Stork,42 and can be used to convert an unfavourable intermolecular reaction into a more favourable and selective intramolecular one. The tether can be easily removed afterwards maintaining the adduct structure that was desired from the original intermolecular reaction.…”

“…During formation of the two arene-alkene carbon σ bonds, this is transformed into a biradical intermediate (41) that then prompts cyclopropane ring closure to make the tricyclic core common to all meta photoadducts.…”

Formation of a Three‐Membered Ring

“…This reaction is better suited to the synthesis of natural products than to intermolecular [3 þ 2] cycloaddition. A carbonyl group in the tether fails to produce any good results, because this chromophore can quench the exciplex between an arene and an alkene [82]. The length of tether length should be (ÀCÀ) 3 or 4 due to the formation of a favorable intramolecular charge-transfer (CT) complex between an arene and an alkene.…”