Studies in organic and physical photochemistry – an interdisciplinary approach

Abstract

Traditionally, organic photochemistry when applied to synthesis strongly interacts with physical chemistry. The aim of this review is to illustrate this very fruitful interdisciplinary approach and cooperation. A profound understanding of the photochemical reactivity and reaction mechanisms is particularly helpful for optimization and application of these reactions. Some typical reactions and particular aspects are reported such as the Norrish-Type II reaction and the Yang cyclization and related transformations, the [2 + 2] photocycloadditions, particularly the Paternò-Büchi reaction, photochemical electron transfer induced transformations, different kinds of catalytic reactions such as photoredox catalysis for organic synthesis and photooxygenation are discussed. Particular aspects such as the structure and reactivity of aryl cations, photochemical reactions in the crystalline state, chiral memory, different mechanisms of hydrogen transfer in photochemical reactions or fundamental aspects of stereoselectivity are discussed. Photochemical reactions are also investigated in the context of chemical engineering. Particularly, continuous flow reactors are of interest. Novel reactor systems are developed and modeling of photochemical transformations and different reactors play a key role in such studies. This research domain builds a bridge between fundamental studies of organic photochemical reactions and their industrial application.

2‐(Hydroxyimino)aldehydes: Photo‐ and Physicochemical Properties of a Versatile Functional Group for Monomer Design

“…To better observe any photoreactions that may occur over longertimescales than that of E/Z interconversion, the photostimulation of compounds 9-11 was continued overnight (22 h). [30] To identify the product originating the new set (see feature 2a bove)o f 1 HNMR signals, we focused on 10,w hich showst he least amountso fr esidual HIA and minor decomposition products.T he full 1 Ha nd 13 CNMR spectra of 10 after 22 hi rradiation, showni nF igure 5, are compatible with the formation of ac yclobutanol oxime (CBO) by Norrish-Yang cyclization, [36] as depicted in Scheme 4. [30] To identify the product originating the new set (see feature 2a bove)o f 1 HNMR signals, we focused on 10,w hich showst he least amountso fr esidual HIA and minor decomposition products.T he full 1 Ha nd 13 CNMR spectra of 10 after 22 hi rradiation, showni nF igure 5, are compatible with the formation of ac yclobutanol oxime (CBO) by Norrish-Yang cyclization, [36] as depicted in Scheme 4.…”

“…The UV/Vis data for the HIAs at 0.1-0.5 mm concentrationi ns everals olvents are presented in the Supporting Information (Table S1). [36] Indeed, both 10 and 12 exhibit aw eak band (e < 100 m À1 cm À1 )a t3 20-334 nm, similarly to a-oxo-oximes. Consistent with the liter-ature on oximes and a-oxo-oximes, [30] all the nonconjugated compounds showa na llowed band at 230-240 nm (e % 10 000 m À1 cm À1 )a scribable to a p!p*t ransition.…”

“…[33] and references therein), who showed that, in addition to E/Z interconversion, photolysis and/oraNorrish type II reaction can take place upon photoexcitation.T he photoreactivity of a-oxo-oximee sters has been known for over ac enturya nd is still being investigated for the photoinitiation of acrylic monomer polymerizations. [36] UV/Vis spectroscopy of HIAs The investigated compounds differ in the bulk of the aliphatic Rg roup (9:R = CH 3 (CH 2 ) 7 -; 10:R = [CH 3 (CH 2 ) 9 ][CH 3 (CH 2 ) 7 ]CH-; 11:R = (CH 3 ) 3 CH-) or in the type of substituent (12:R = CH 2 = C(CH 3 )CO 2 (CH 2 ) 4 -; 14:R = Ph).…”

“…Based on the evidence presented in this paper and on the behavior of a-oxo-oximes documented by Buys et al, [35] we identified this product as ac yclobutanol oxime (CBO) derivative (Scheme 4) formed by Norrish-Yang cyclization. [36] UV/Vis spectroscopy of HIAs…”

“…The spectra of concentrated (up to 1.2 mm) solutions of 10 and 12 in DMSO were also recorded to check for the presence of ab and ascribable to the forbidden n!p* transition. [36] Indeed, both 10 and 12 exhibit aw eak band (e < 100 m À1 cm À1 )a t3 20-334 nm, similarly to a-oxo-oximes. [30] Following deprotonation with (CH 3 ) 4 NOH as the base, an ew peak appearsa t2 90-300 nm due to the p!p*a bsorption bands of HIA anions, in which the negative chargei sd elocalized as depicted in Figure 3.…”