Light-promoted oxidation of aldehydes to carboxylic acids under aerobic and photocatalyst-free conditions

Abstract

The development of green and sustainable methods for the conversion of aldehydes to carboxylic acids is of high academic and industrial interest. We demonstrate herein a practical and efficient light-promoted...

Comment on “Photoinduced Protocol for Aerobic Oxidation of Aldehydes to Carboxylic Acids under Mild Conditions”

“…From the above presented published results ,− and discussions of the data presented by Li et al, we cannot conclude, in the present state of research, that photo-oxidation using 360 nm LED is an effective alternative aerobic oxidation methodology for benzaldehyde aerobic oxidation in water. Oxygen availability has been identified as a key factor limiting oxidation in water, and the use of inadequate glassware, i.e., a 15 mL test tube with 2 mL of water, does not allow for efficient oxygen mass transfer into the aqueous phase, making it difficult to compare with previously described methods.…”

“…The time to reach such a relatively low yield could be compared with previously published experimental conditions (Table ). Light-promoted oxidation of benzaldehyde without a photocatalyst, using air as the oxidant in an acetone/water mixture, gave a similar yield but in a shorter time, i.e., 7 h vs 30 h (Table , entry 2) . Using acetonitrile as the solvent and organocatalyst, , higher yields were obtained in a shorter time (Table , entries 3 and 4).…”

“…Light-promoted oxidation of benzaldehyde without a photocatalyst, using air as the oxidant in an acetone/water mixture, gave a similar yield but in a shorter time, i.e., 7 h vs 30 h (Table 1, entry 2). 18 Using acetonitrile as the solvent and organocatalyst, 19,20 higher yields were obtained in a shorter time (Table 1, entries 3 and 4). A similar yield could be obtained in water using 0.1 mol % Fe III Mo 6 as the catalyst (Table 1, entry 5).…”

Photo-induced decarboxylative hydroacylation of α-oxocarboxylic acids with terminal alkynes by radical addition–translocation–cyclization in water

“…3 Since then, many elegant organic transformations including the Mukaiyama aldol reaction, 4 a the Claisen rearrangement, 4 b the Barbier–Grignard-type arylation, 4 c asymmetric catalysis 4 d – f and cross-coupling reactions 4 g have been developed using water as the reaction medium. 4 Furthermore, visible light is considered to be an inexpensive, clean, non-polluting and abundant renewable resource, which has been utilized as an alternative to fossil fuels for achieving novel and valuable organic transformations. In the past few years, considerable efforts have been directed toward the incorporation of visible light photoredox strategies into organic synthesis and great success has been achieved.…”

Response to Comment on “Photoinduced Protocol for Aerobic Oxidation of Aldehydes to Carboxylic Acids under Mild Conditions”

“…9 Kokotos and co-workers described a light-promoted method for oxidation of aldehydes using atmospheric oxygen as the sole oxidant. 10 Just like our protocol, all these methods also require base and acid treatments and extractions with organic solvent in the post-treatment process. However, the authors of these papers still think the reaction conditions are greener because the chromatographic purification process, which requires more time and large amounts of organic solvents, was avoided.…”