Photoinduced Molecular Transformations. Part 154. On the Mechanism of the Formation of the 5-Iodopentyl Formate in the Photolysis of Cyclopentanol Hypoiodite in Solution in the Presence of Mercury(II) Oxide-Iodine.
(18)O-labelling experiments established that the formation of 5-iodopentyl formate in the photolysis of cyclopentanol hypoiodite in the presence of excess mercury(II) oxide-iodine in benzene involves the following pathway: a) a β-scission of a cyclopentyloxy radical to rearrange to a primary 5-oxopentyl radical, which generates the corresponding carbocation by a metal ionassisted one-electron oxidation; b) an intramolecular addition of the 5-oxopentyl cation to the formyl oxygen to generate a tetrahydropyranyl cation; c) a combination of the tetrahydropyranyl cation with diiodine oxide (I2O) to form a lactol hypoiodite; d) generation of a carbon-centred radical by a selective β-scission of a carbon-carbon bond of an alkoxyl radical generated from the lactol hypoiodite; e) abstraction of an iodine by the carbon-centred radical from an iodine molecule to form the 5-iodopentyl formate. 5-Iodopentyl formate is also produced by prolonged irradiation of a solution of 5-iodopentanal in the presence of mercury(II) oxide and iodine in benzene with Pyrex-filtered light.The formate in this case should be formed through the generation of the 5-oxopentyl cation (mentioned above) by mercury-assisted ionization of its carbon-iodine bond, followed by the same pathway as that mentioned above.
Suginome, Hiroshi,Senboku, Hisanori
p. 13101 - 13112
(2007/10/02)
Alkoxyl radicals from alcohols I. The hypoiodite reaction of cyclopentanol: Evidence for sequential rather than competitive reaction pathways
The representative photostimulated hypoiodite reaction of cyclopentanol with mercury(II) oxide and iodine gives products formed by a sequence of iodoaldehyde formation, followed by consumption to give Baeyer-Villiger and hydrolysis products.
Courtneidge
p. 3053 - 3056
(2007/10/02)
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