A new approach to substituted arene oxides. Total synthesis of senepoxide and seneol

Free Radical Chemistry of β-Lactones. Arrhenius Parameters for the Decarboxylative Cleavage and Ring Expansion of 2-Oxetanon-4-ylcarbinyl Radicals. Facilitation of Chain Propagation by Catalytic Benzeneselenol

“…We then turned to the reaction of bromolactones with stannanes. Substrate 7 was prepared by hydrogenation of the β-lactone 6, 35 which, in turn, like 8 24 was obtained from the seco acid by bromolactonization. A further bromo-β-lactone 12 was obtained by Wittig olefination of 9, 36 followed by saponification, and kinetic bromolactonization (Scheme 4).…”

Enantiospecific Syntheses of (+)-Crotepoxide, (+)-Boesenoxide, (+)-β-Senepoxide, (+)-Pipoxide Acetate, (−)-iso-Crotepoxide, (−)-Senepoxide, and (−)-Tingtanoxide from (−)-Quinic Acid1

“…Approaches toward (±)-crotepoxide ( 1 ) were based on transformations from a quinone, a 1,4-cyclohexadiene or a styrene derivative . The first approach was also used to obtain (±)-senepoxide ( 7 ), and the second approach afforded iso - crotepoxide ( 6 ), (±)-senepoxide ( 7 ), (±)-β-senepoxide ( 3 ), and (±)-pipoxide ( 4 ) . A Diels−Alder route was employed by Schlessinger to synthesize (±)-senepoxide ( 7 ) and to provide formal syntheses of (±)-crotepoxide ( 1 ) and (±)-pipoxide ( 4 ) .…”

Formation of Four-Membered Heterocycles through Electrophilic Heteroatom Cyclization

“…The same group found that β‐lactones 16 were also easily obtained under the same conditions (Br 2 , NaHCO 3 ) from 1‐substituted 1,4‐dihydrobenzoic acids 15 13. As noted above, the β‐lactones are kinetic products, and on heating they smoothly rearranged into the thermodynamically more stable β‐bromo‐γ‐lactones 17 (Scheme ).…”

“…Bicyclic β‐lactones can be viewed as useful synthetic intermediates: they may be transformed, for example, into arenes 21 (after dehydrobromination and subsequent carbon dioxide extrusion),11 into arene oxides 22 ,13 or into 1,3‐diols 23 (after lithium aluminiumhydride reduction of the lactone and bromine substitution) (Scheme ) 15.…”