Herein we report a one-pot deoxygenation protocol for primary and secondary alcohols developed via the combination of the Garegg-Samuelsson reaction, visible light-photoredox catalysis, and flow chemistry. This procedure is characterized by mild reaction conditions, easy-to-handle reactants and reagents, excellent functional group tolerance, and good yields.

Despite the great achievements of advanced photoredox catalysis for organic‐synthetic reactions, the literature is rather vague with respect to reaction quantum yields – the number of product molecules per absorbed photon. This stands in contrast to the clear and commonly used chemical yield as standard parameter to quantify the efficiency of chemical reactions. We applied an opto‐electronic device to measure the reaction quantum yields of a reference reaction in a rapid and facile way, which revealed that this parameter cannot be regarded as a single, isolated value. A so far undescribed strong dependence of the reaction quantum yield on the incident light power and the irradiation time was revealed. The light input even decides on the interplay of the closed photoredox catalytic cycle and the radical chain propagation. The reaction kinetics were modelled in full detail to obtain important insight into the general description of photoredox catalytic mechanisms.

Five core-substituted naphthalene diimides bearing two dialkylamino groups were synthesized as potential visible light photoredox catalysts and characterized by methods of optical spectroscopy and electrochemistry in comparison with one unsubstituted naphthalene diimide as reference. The core-substituted naphthalene diimides differ by the alkyl groups at the imide nitrogens and at the nitrogens of the two substituents at the core in order to enhance their solubility in DMF and thereby enhance their photoredox catalytic potential. The 1-ethylpropyl group as rather short and branched alkyl substituent at the imide nitrogen and the n-propyl group as short and unbranched one at the core amines yielded the best solubilities. The electron-donating diaminoalkyl substituents together with the electron-deficient aromatic core of the naphthalene diimides increase the charge-transfer character of their photoexcited states and thus shift their absorption into the visible light (500–650 nm). The excited state reduction potential was estimated to be approximately +1.0 V (vs SCE) which is sufficient to photocatalyze typical organic reactions. The photoredox catalytic activity in the visible light range was tested by the α-alkylation of 1-octanal as benchmark reaction. Irradiations were performed with LEDs in the visible light range between 520 nm and 640 nm. The irradiation by visible light together with the use of an organic dye instead of a transition metal complex as photoredox catalyst improve the sustainability and make photoredox catalysis “greener”.

Batch to Flow Deoxygenation Using Visible Light Photoredox Catalysis. -A catalytic one-pot deoxygenation protocol for primary and secondary alcohols (I) that shows high functional group tolerance is developed. The method consists of a Garegg-Samuelsson reaction to generate the alkyl iodide, which is in turn subjected to continuous flow under visible light irradiation to effect the hydrodeiodination. -(NGUYEN, J. D.; REISS, B.; DAI, C.; STEPHENSON*, C. R. J.; Chem. Commun. (Cambridge) 49 (2013) 39, 4352-4354, http://dx.

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