Photochemistry of imines: concerning the formation of dihydrophotodimers from N-diphenylmethylenebenzylamine

Abstract

When alcohol solutions of N-diphenylmethylenebenzylamine (Id) are irradiated in the presence of benzophenone with light of intensity -200 W there is predominant formation of the ~r~~syttlnletrical dihydrophotodimer (4) and no symmetrical dimers are detected. The dihydromonomer (2d) is also produced. However, when a more intense light source (450 W) is used no dirner of any sort is formed although the dihydromonomer is still produced. The formation of the unsyninietrical dihydrodimer (4) cannot be attributed entirely to secondary reactions of the dihydromonomer (2d) since irradiation of the latter produces both symmetrical (7) and unsynimetrical (4) dihydrodimers in the ratio 1 :2.

Studien zum Vorgang der Wasserstoffübertragung, XXXIV1) Elektrochemische Hydrodimerisierung von Schiffbasen

“…0.8 -1.3 sind mit denen vergleichbar, die bei der Elektropinakolisierung von Alkyl(ary1)ketonen in sauren Mediensl), der Photohydrodimerisierung von Carbonylverbindungen52) und Azomethinens3. 54 Das Fehlen jeglicher optischer Aktivitat in den reinen Hydrodimeren spricht weiterhin gegen den ionischen Hydrodimerisierungsmechanisrnus, die Addition eines Carbanions an nicht umgesetztes Azomethin, da die erfolgreichen enantioselektiven elektrochemischen Reduktionen prochiraler Azomethine in Gegenwart chiraler Leitsalzkationen (s. unten) auf chirale, zumindest partiell konfigurationsstabile Carbanionen schlieRen lassen.…”

Birefringence and Orientation Direction Control of Photoalignable Liquid Crystalline Copolymer Films Based on In Situ Modification of Mesogenic Groups

“…Several phenylimine derivatives exhibit photodegradation and photodimerization under UV-light exposure. ,− In addition to the photoisomerization and photoreaction of CA, a partial side-photoreaction of FL-NBA may occur which are confirmed by FT-IR spectroscopy (Figure S3b). Photoexposure induces an absorption band of CHO at 1699 cm –1 , whereas those of CN and CC at 1627 cm –1 decrease, indicating photodegradation.…”

Photochemical reduction in the N-acylketimine system

“…Extended irradiation of 13 in benzene, however, resulted in the complete recovery of starting material. The failure of 13 to form a type II product on irradiation in benzene prompted us to examine the photochemistry of N-[«-(2,2-dimethylbutyl)benzylidene]benzamide (15). In this case, a type II reaction would involve hydrogen transfer from a more reactive secondary position.…”

“…Preparation of JV-[a-(l,l-Dimethylbutyl)benzylidene]benzamide (15). A solution containing 2.75 g of bromobenzene in 40 ml of anhydrous ether was added to a three-neck flask which contained 0.425 g of magnesium turnings in 5 ml of ether.…”