Auto-tandem PET and EnT photocatalysis by crude chlorophyll under visible light towards the oxidative functionalization of indoles

Abstract

Chlorophyll is the most abundant photocatalytic pigment that enables plants to absorb solar energy and convert it to energy storage molecules. Herein, we report a tandem photocatalytic approach utilizing the...

Red light-induced highly efficient aerobic oxidation of organoboron compounds using spinach as a photocatalyst

“…Having established the optimal reaction conditions, the scopes and limitations of this transformation were examined as illustrated in Scheme 2. A series of phenylboronic acids underwent oxidative hydroxylation smoothly to provide the corresponding alcohols with excellent yields regardless of their electronic properties and substitution positions (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Polysubstituted phenylboronic acid was also suitable (23).…”

“…Chlorophyll, as the main photoreceptor in spinach and other green plant chloroplasts, is the most "green" photocatalyst, since it shows excellent characteristics in the utilization of light and oxygen. 1 In recent years, the use of chlorophyll as an efficient photocatalyst has developed rapidly for visible lightinduced organic synthesis reactions, such as catalyzing free radical polymerization, 2,3 sp 3 C-H bond functionalization, 4,5 oxidative functionalization, [6][7][8][9] the Biginelli reaction, 10 the Barton-McCombie reaction, 11 etc. Actually, chlorophyll exhibits a strong absorption band at 680 nm, suggesting that it may promote photocatalysis under low-energy red light, which allows greater penetration into various kinds of organisms and avoids unwanted side reactions.…”

Chlorophyll: the ubiquitous photocatalyst of nature and its potential as an organo-photocatalyst in organic syntheses

“…5 UV-Vis spectroscopy of crude chlorophyll extracts dissolved in 90% acetone/water (triple distilled water). 18 Fig. 6 Prospective chlorophyll-catalyzed visible light photocatalysis; oxidative and reductive quenching cycles of chlorophyll and energy transfer process with oxygen.…”

“…Recently, our group reported an environmentally friendly, chlorophyll-catalyzed visible light-mediated aerobic reaction protocol for oxidizing indoles (Scheme 19a). 18 Crude Chl a obtained from spinach leaves and acetone extracts was directly used as the photocatalyst. The concentration of Chl a in crude chlorophyll solution was estimated by performing UV-Vis spectroscopy by following the Wellburn method.…”

“…Common methods employed for this organic transformation require the use of either transition metals [OsO 4 and CrO 3 ] or organic oxidants like N-bromosuccinamide (NBS) or meta-perchlorobenzoic acid (mCPBA). Recently, our group reported an environmentally friendly, chlorophyll-catalyzed visible lightmediated aerobic reaction protocol for oxidizing indoles (Scheme 19a) 18. Crude Chl a obtained from spinach leaves and acetone extracts was directly used as the photocatalyst.…”