Intramolecular Photocycloaddition of 2-(2-Alkenyloxymethyl)naphthalene-1-carbonitriles Using Glass-Made Microreactors

Abstract

Intramolecular [2+2] and [2+3] photocycloadditions of 2-(2-alkenyloxymethyl)naphthalene-1-carbonitriles and their photocycloreversion using glass-made microreactors were investigated in comparison with photoreactions under conventional batch conditions. Both the efficiency and regioselectivity were improved by use of glass-made microreactors. These results can be explained by thorough absorption of light and outflow of primary product from the reaction system.

Continuous flow reactors: a perspective

“…Maeda et al 54 subsequently investigated the intramolecular [2+2] and [2+3] photocycloaddition of 2-(2-alkenyloxymethyl)-naphthalene-1-carbonitriles, comparing the efficiency of reactions performed under standard and flow conditions (Channel dimensions = 2.5 mm (wide) ¥ 60 mm (long)); employing a Xenon lamp (500 W, l = 280 nm) (Scheme 16). Performing the reaction under flow conditions the authors were able to uniformly irradiate the reaction mixture, which not only reduced the irradiation time from 240 min to 1 min, but also minimised the proportion of photocycloreversion observed.…”

Diastereodifferentiating [2+2] photocycloaddition of chiral cyclohexenone carboxylates with cyclopentene by a microreactor

“…Furthermore, the very narrow reaction channel in the microreactor provides for very high light penetration through the samples based on the Beer-Lambert law. This superior light penetration in the microreactor enables the photoreaction to proceed smoothly, and a number of photoreactions using the flow chemistry concept have been reported at lab-level [19][20][21] as well as in industrial processes [22][23][24]. We previously performed diastereodifferentiating [2+2] photocycloaddition in a microreactor irradiated by a 500-W high-pressure mercury lamp and shortened the reaction time by half compared to the result in a batch reactor [25].…”

Photocycloaddition of four homologous 2-(cycloamino)propenenitriles to 1-acetonaphthone

“…Reversibility of intramolecular [2+2]-photocycloadditions of double bonds to the 1-cyanonaphthalene system, preceding the [3+2]-photocycloaddition, have also been observed by Mizuno et al 22,23 The course of the observed photocycloadditions Monochromatic (313 nm) excitation of a common equimolar solution of 1 and model compound 2 in acetonitrile had shown a marked decrease of the absorbance between 250 and 290 nm and no isosbestic points over the wavelength range 240-380 nm in the reaction spectrum, demonstrating that only products of lower absorbance than that of either starting material are produced. The graphical evaluation of the reaction spectrum gave linear absorbancy-time and absorbancy diagrams 43 .…”