Novel [4-Hydroxy-TEMPO + NaCl]/SiO2 as a Reusable Catalyst for Aerobic Oxidation of Alcohols to Carbonyls

Abstract

A convenient method for the preparation of [4-hydroxy-TEMPO + NaCl]/SiO 2 was developed. And [4-hydroxy-TEMPO + NaCl]/SiO 2 with Fe(NO 3 ) 3 ·9H 2 O was used for an aerobic oxidation of alcohols to carbonyls under mild reaction conditions. Alcohols were converted to the corresponding carbonyls in good to excellent yields. [4-Hydroxy-TEMPO + NaCl]/SiO 2 can be easily separated from the reaction mixture by filtration and reused at least six times.

Pyrethroid insecticides. Chapter III: Synthesis of 3-phenoxy mandelonitrile

“…Synthesis of 4-phenoxybenzaldehydes. 178,211 Thus, the carboxylic acid 4e has been successfully transformed to 3-phenoxybenzaldehyde 4a using the Rosenmund reduction 206 that involves the transformation to the corresponding acid chloride 4j on reaction of thionyl chloride in DMF at reflux and its reduction with hydrogen in the presence of palladium on charcoal as catalyst (Scheme 61, entry a). 178 The transformation of 3-phenoxybenzyl alcohol (4c) to 3-phenoxybenzaldehyde (4a) discussed in Section 3.4.2.…”

“…Selective oxidation of alcohols to the corresponding aldehydes is a ubiquitous transformation in organic chemistry 196, that include several named reactions such as Swern oxidation, Moffat oxidation, Jones oxidation, Corey-Suggs oxidation, Dess-Martin oxidation (references cited). 211 It has been traditionally achieved by numerous stoichiometric oxidants, often involving transition metals, that lead to the release of quantities of toxic by-products into the environment. Molecular oxygen as a pure substance or diluted in air and hydrogen peroxide offer several advantages since they are environmentally friendly and exhibit a high efficiency per weight of oxidant.…”

“…Aerobic oxidation of 3-phenoxybenzyl alcohol (4c) to 3-phenoxybenzaldehyde (4a), involving metal catalysis and iodosyl benzene , TEMPO or TCQ as oxidant. 211,213,[225][226][227][228][229] 3.4.2.2.1. Palladium-promoted oxidation of 3-phenoxybenzyl alcohol.…”

“…Most of the conditions use catalytic amount of TEMPO and therefore require the in situ oxidation of the resulting TEMPOH (84a) by-product. This has been effectively achieved by dioxygen (Scheme 75, entry f) 226 or air (Scheme 78, entries g-i) 211,227,228 in some cases in the presence of transition metal catalysts (iron or copper, Scheme 75, entries h,i). 211,227 Originally the oxidation of TEMPO required the presence of a transition metal catalyst and several conditions have been tested in order to perform the aerobic oxidation reaction under mild metal-free conditions.…”

“…This has been effectively achieved by dioxygen (Scheme 75, entry f) 226 or air (Scheme 78, entries g-i) 211,227,228 in some cases in the presence of transition metal catalysts (iron or copper, Scheme 75, entries h,i). 211,227 Originally the oxidation of TEMPO required the presence of a transition metal catalyst and several conditions have been tested in order to perform the aerobic oxidation reaction under mild metal-free conditions. Among the various combinations tested, 226,228 two high yielding conditions have been selected for the oxidation of 3-phenoxybenzyl alcohol (4c).…”