Visible light-promoted dihydroxylation of styrenes with water and dioxygen

Abstract

An efficient visible light promoted metal-free dihydroxylation of styrenes with water and dioxygen has been developed for the construction of vicinal alcohols. The protocol was operationally simple with a broad substrate scope. The mechanistic studies demonstrated that one of the hydroxyl groups came from water and the other one came from molecular oxygen. Additionally, the β-alkyoxy alcohols could also be obtained using a similar strategy.

Redox Potential Controlled Selective Oxidation of Styrenes for Regio- and Stereoselective Crossed Intermolecular [2 + 2] Cycloaddition via Organophotoredox Catalysis

“…According to the excited state reduction potentials of representative organophotoredox catalysts and oxidation potentials of styrenes (Scheme ), , eosin Y, Rose Bengal, and fluorescein cannot oxidize trans -anethole 1a due to their low excited state reduction potentials ( E 1/2 (C*/C •– ) = +0.77 to +0.88 V vs SCE). In contrast, Acr + -Mes and TPT, which have high excited state reduction potentials ( E p/2 (C*/C •– ) = +2.08 and +2.55 V vs SCE, respectively), can oxidize not only trans -anethole 1a but also styrene 2a ( E p/2 = +1.97 V vs SCE); thus, it is difficult to selectively oxidize trans -anethole. Therefore, as only a few organophotoredox catalysts can be applied to oxidative crossed [2 + 2] cycloadditions of styrenes, i.e., 4CzIPN ( E 1/2 (C*/C •– ) = +1.35 V vs SCE), development of more efficient photocatalytic systems is highly desirable.…”

Photo‐Induced Dihydroxylation of Alkenes with Diacetyl, Oxygen, and Water

“…The reaction in ethanol afforded 2-ethoxy-2-phenyl-1-propanol (25) in 33 % yield, being in contrast to the previous photo-induced dihydroxylation reaction, which showed an opposite regioselectivity, giving 1-alkoxy-2-phenyl-2-propanol from 23. [9] In order to gain mechanistic insights, the dihydroxylation reaction of 1 was performed in water- 18 O. The product 2-18 O incorporated only one 18 O isotope, which was confirmed by high resolution mass spectrometry (Scheme 6,a).…”

“…Lu reported a dihydroxylation reaction which uses oxygen, water, visible light, and an acridinium photoredox catalyst (Scheme 1,b). [9] It proceeds through a radical pathway under mild reaction conditions; however, the eligible substrates are limited to styrene derivatives. Herein described is a benign protocol for dihydroxylation which uses diacetyl (= butane-2,3-dione), oxygen, water, and visible light.…”

Syn-Dihydroxylation of Alkenes Using a Sterically Demanding Cyclic Diacyl Peroxide

“…1 H­{ 13 C} NMR (400 MHz, CDCl 3 ): δ = 7.44–7.32 (m, 4H), 7.29–7.23 (m, 1H), 3.98 (d, J = 11.2 Hz, 1H), 3.81 (d, J = 11.3 Hz, 1H), 2.66 (s, 1H), 2.11–1.97 (m, 1H), 1.61 (br s, 1H), 0.92 (d, J = 6.8 Hz, 3H), 0.75 (d, J = 6.9 Hz, 3H) ppm. 13 C­{ 1 H} NMR (100 MHz, CDCl 3 ): δ = 142.9, 128.2, 127.0, 126.2, 79.3, 68.4, 35.2, 17.4, 16.7 ppm …”

“…1 H­{ 13 C} NMR (400 MHz, CDCl 3 ): δ = 7.42–7.31 (m, 4H), 7.28–7.22 (m, 1H), 3.96 (d, J = 10.9 Hz, 1H), 3.81 (dd, J = 11.2, 7.6 Hz, 1H), 2.72 (s, 1H), 1.85–1.54 (m, 6H), 1.47–1.38 (m, 1H), 1.28–0.9 (m, 5H) ppm. 13 C­{ 1 H} NMR (100 MHz, CDCl 3 ): δ = 143.1, 128.1, 126.9, 126.2, 79.2, 68.1, 45.6, 27.2, 26.8, 26.6, 26.5, 26.3 ppm …”