153851-08-2Relevant academic research and scientific papers
Photoinduced Molecular Transformations. Part 144. One-Carbon Intercalation of γ- and δ-Lactones involving the β-Scission of Alkoxyl Radicals as the Key Step: Synthesis of δ- and ε-Lactones with α-Substituents
Kobayashi, Kazuhiro,Minakawa, Hiroki,Sakurai, Hideo,Kujime, Sachiko,Suginome, Hiroshi
, p. 3007 - 3010 (2007/10/02)
A new general method of a one-carbon intercalation of γ-lactones to δ-lactones and δ-lactones to ε-lactones in three steps involving a selective β-scission of the alkoxyl racicals as the key step is described.The reactions of γ- and δ-lactones with lithioalkyl acetate gave an equilibrium mixture of alkyl (2-hydroxytetrahydrofuran-2-yl)acetates and alkyl (2-hydroxytetrahydropyran-2-yl)acetates, as well as their ring-opened isomers in 62-95percent yields, respectively.The photolysis of the hypoiodites of these lactols in benzene containing mercury(II) oxide and iodine with Pyrex-filtered light resulted in a selective endocyclic β-scission of the corresponding alkoxyl radicals to give alkyl iodoalkyl propanedioates in 33-70percent yields.Treatment of the iodoalkyl propanedioates with tetraethylammonium bromide and sodium hydride gave alkyl 3,4,5,6-tetrahydro-2-oxo-2H-pyran-3-carboxylates or alkyl 2,3,4,5,5a,6,7,8,9,9a-decahydro-2-oxobenzoxepine-3-carboxylate in 61-81percent yields.On the other hand, succesive treatment of ω-iodoalkyl propanedioates with tetraethylammonium bromide-sodium hydride and then benzyl bromide gave a α-disubstituted δ-lactone, which gave a α-monosubstituted δ-lactone upon heating in trifluoroacetic acid under reflux.Cyclopentanone can similarly be transformed into 2-substituted cyclohexanone via a three-step procedure.
