The direct anti-Markovnikov addition of strong Brønsted acids to alkenes remains an unsolved problem in synthetic chemistry. Here, we report an efficient organic photoredox catalyst system for the addition of HCl, HF and also phosphoric and sulfonic acids to alkenes, with complete regioselectivity. These transformations were developed using a photoredox catalyst in conjunction with a redox-active hydrogen atom donor. The nucleophile counterion plays a critical role by ensuring high reactivity, with 2,6-lutidinium salts typically furnishing the best results. The nature of the redox-active hydrogen atom donor is also consequential, with 4-methoxythiophenol providing the best reactivity when 2,6-lutidinium salts are used. A novel acridinium sensitizer provides enhanced reactivity within several of the more challenging reaction manifolds. This Article demonstrates how nucleophilic addition reactions mediated by photoredox catalysis can change the way electrophilic and homofugal precursors are constructed.

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The Direct anti-Markovnikov Addition of Mineral Acids to Styrenes. -Efficient procedures are elaborated for the anti-Markovnikov addition of HCl, HF, phosphoric acids, and sulfonic acids, to alkenes in the presence of a photoredox catalytic system containing an acridinium sensitizer. -(WILGER, D. J.; GRANDJEAN, J.-M. M.; LAMMERT, T. R.; NICEWICZ*, D. A.; Nat. Chem. 6 (2014) 8, 720-726, http://dx.

The use of an academic half day (AHD) compared to a traditional noon conference (NC) has been studied in graduate medical education. Despite undergraduate medical education (UGME) use of AHDs there is no data to advocate for this teaching strategy. We explored the impact of an AHD on UGME during the pediatric clerkship rotation. During the 2017-18 academic year, 118 third-year medical students rotated on the pediatric clerkship rotation. Fifty-eight students were placed in the NC format and 60 in the AHD. NBME Subject Examination performance is similar for both groups (0.04 vs 0.23, F(1, 116)=1.31, p > 0.26). Attendance was significantly higher for AHD compared with NC (90.9% vs 73.3%, F(1, 114)=63.27, p<0.05). Additionally, the mean didactic rating is 3.81 for the AHD group, significantly higher than 3.60 for the NC group (F(1, 113)=6.56, p <0.05). The impact of an AHD in UGME appears promising and consistent with experiences of an AHD in graduate medical education on medical knowledge, attendance, and didactic satisfaction.