Preparation of formyl‐deuterated benzaldehydes by direct photo‐deuteration or by photolysis of phenylglyoxylic acid

Abstract

SummaryTwo new photochemical methods are described to prepare D-I-benzaldehydes of high isotopic purity in good yield. The comprehensive treatise of deuteration techniques and

Aldehydes as powerful initiators for photochemical transformations

“…These studies illuminate the ways that the various excited states of benzaldehyde (8) decay, either through phosphorescence or through the dissociation to benzene (21) and carbon monoxide (22) or to a benzoyl radical (10) and a hydrogen atom (reactions (2) and (3) in Scheme 5). A practical application of these studies can be seen in the work of Kuhn et al, who demonstrated the use of the dissociation properties of benzaldehyde (8) and phenylglyoxylic acid in order to achieve highly deuterated products, which were more stable than the undeuterated ones upon irradiation and subsequent excitation [27,28]. The excited triplet state T 1 (n,π * ) of carbonyl compounds tends to be the most reactive state (compared to the singlet state).…”

“…In 1978, McGinniss and co-workers reported the polymerization of methyl methacrylate (26, MMA) by employing 4,4'bis(N,N-diethylamino)benzophenone (27, DEABP) as the photoinitiator (Scheme 7) [35]. It was already well-accepted that aminoaromatic compounds, such as Michler's ketone (28) and DEABP (27), present large extinction coefficients and charge transfer states as well as relatively long-lived triplet states in solution, making them suitable as photoinitiators [36,37].…”

“…The irradiation and excitation of DEABP (27) to the singlet state is followed by intersystem crossing to the triplet state 29, which then leads to two different types of free radical intermediates, 30 and 31 (Scheme 8). The species 31 was shown to be the primary initiating radical compound.…”

Catalytic Oxidative Cleavage of 1,3-Diketones to Carboxylic Acids by Aerobic Photooxidation with Iodine

“…zil (27) 11 and glyoxylic acid (28) 12 were converted into perbenzoic acid (29). Finally, perbenzoic acid (29) was reduced to benzoic acid (2).…”

Recent Advances in the Practical Synthesis of C1 Deuterated Aromatic Aldehydes Enabled by Catalysis and Beyond

“…However, the common Isotopic labelling procedures for obtaining deuterated aldehydes entail the use of reagents such as LiAlD 4 , deuterated Schwartz's reagent (Cp 2 ZrDCl), D 2 gas with iridium catalysts, or D 2 O with Ru catalysts and Pd/Ru with D 2 O, CO. Moreover, recent catalytic methods, [11–23] for the formation of deuterated aldehydes (aldehyde‐ d ) are restricted in their practical application due to harsh reaction conditions, unselective reactions, limited substrate scopes, low reagent availability, higher amount of base and catalyst, and less deuterium incorporation. These restrictions are particularly severe for aldehydes containing polar or electron‐withdrawing substituents, which are prone to side reactions.…”