Facile, green, and functional group-tolerant reductions of carboxylic acids…in, or with, water

Abstract

Facile reductions of carboxylic acids to aldehydes or alcohols can be effected under mild conditions upon initial conversion to their corresponding S-2-pyridyl thioesters. Upon treatment with a commercially available and...

On the role of surfactants: rethinking “aqueous” chemistry

“…30 The same 2-pyridyl thioester intermediates can be reduced to either the aldehyde, or perhaps more noteworthy, the alcohol, thereby avoiding use of potentially dangerous LAH, especially on scale (Scheme 4). 31 In addition to amides, aldehydes, and alcohols, both esters and thioesters appeared to be reasonable targets, and indeed, after some additional experimental work, both functional groups are now realizable using the same thioester precursors (see paper dedicated to solely this subject, herein). 32 Esters are formed under either neat conditions, or by adding the alcohol (1.05 equiv.)…”

Use of dipyridyldithiocarbonate (DPDTC) as an environmentally responsible reagent leading to esters and thioesters under green chemistry conditions

“…This includes their transformation into several other derivatives (e.g., amides, aldehydes, and alcohols). 32,35 Also worthy of note is that, in addition, treatment of 2-pyridyl thioester intermediates under aqueous micellar conditions is also an option leading to the desired product (see compound 10). Targets such as 4 (bezafibrate), 6 ( probenecid), 7 (indomethacin), 10 (naproxen), 8 and 12 (fenofibric acid), and 13 (ciprofibrate) could all be made from the associated drug-related carboxylic acids, each being realized in moderate-to-good yield.…”

Palladium-Catalyzed Aminations in Flow ... on Water

“…41 After a workup, the crude intermediate was then subjected to flow conditions (step 2 in Scheme 7) leading to dipyridylamine 29. Then, reduction of the ketone using NaBH 4 in EtOH (step 3 in Scheme 7) led to the corresponding secondary alcohol, 42 from which EtOH was removed in vacuo. Without isolation, aqueous TPGS-750-M was added and used as the reaction medium for subsequent esterification with 4-bromobenzoyl chloride (step 4 in Scheme 7).…”