A General Approach to Catalytic Alkene Anti-Markovnikov Hydrofunctionalization Reactions via Acridinium Photoredox Catalysis

• DOI: 10.1021/acs.accounts.6b00304
• Publication Date: 2016-09-02T15:33:32Z
• Authors: Kaila A. Margrey; David A. Nicewicz
• Keywords: Markovnikov's rule; Alkene; Photoredox catalysis

The development of methods for anti-Markovnikov alkene hydrofunctionalization has been a focal point catalysis research several decades. vast majority work on the control regioselectivity this reaction class hinged transition metal catalyst activation olefin substrates. While progress realized, there are significant limitations to approach, and general solution reactions olefins does not presently exist. In past years, lab focused by single electron oxidation using organic photoredox catalysts facilitate hydrofunctionalization. By accessing reactive cation radical intermediates, we have realized truly approach reactions. We identified dual system consisting an acridinium photooxidant, first reported Fukuzumi, redox-active hydrogen atom donor that accomplishes wide range with complete regiocontrol. This method relies reverse its polarity results in opposite 2012, disclosed hydroetherification alkenols employing photocatalyst proceeds via interwoven polar steps. enabled important area, including hydroacetoxylation, hydrolactonization, hydroamination, hydrotrifluoromethylation More recently, also delineated conditions intermolecular hydroamination alkenes either triflamide or nitrogen-containing heteroaromatic compounds such as pyrazole, indazole, imidazole, 1,2,3-triazole. Further led addition mineral acids lutidinium halide salts convenient reagents deliver acids. Acids HCl, HF, H3PO4, MeSO3H all participate reactions, even highly prone polymerization. A combination transient steady-state absorption spectroscopy tools were employed observe radicals resultant acridine radical, lending support transfer mechanism. origin selectivity these is likely result reversible nucleophile resulting greater population more stable radical. Loss proton followed intermediate completes transformations. Again, means spectroscopy, oxidative turnover was observed catalytic cycle mechanistic picture.