Red light has the advantages of low energy, less health risk and high penetration depth through various media. Herein, a helical carbenium ion (N,N'-din -propyl-1,13-dimethoxyquinacridinium (nPr-DMQA+) tetrafluoroborate) has been used as an organic photoredox catalyst for photoreductions and photooxidations in the presence of red ligh (max = 640 nm). It has catalyzed red-lightmediated dual transition-metal/photoredox-catalyzed C-H arylation and intermolecular atom transfer radical addition through oxidative quenching, affording products in 57-93% yields. Moreover, its potential in photooxidation catalysis has also been demonstrated by successful applications in red-light-induced aerobic oxidative hydroxylation of arylboronic acids and benzylic C(sp3)-H oxygenation through reductive quenching, delivering products in up to 92% yield. Thus, a versatile organic photoredox catalyst (helical carbenium ion) for red-light-mediated photoredox reactions has been developed. In summary, we have disclosed a helical carbenium ion [nPr-DMQA+][BF4-] (3), which catalyzes photoreductions and photooxidations in the presence of low-energy red light. The role of 3 as an efficient PC in oxidative and reductive quenching were evaluated by transition-metal/nPr-DMQA+-catalyzed C-H arylations and intermolecular ATRA (oxidative quenching), as well as aerobic oxidative hydroxylation of arylboronic acids and benzylic C(sp3)-H oxygenation (reductive quenching). Eight diverse substrates were well-tolerated for red-light-mediated dual Pd/nPr-DMQA+-catalyzed C(sp2)-H arylation. Moreover, with twelve different arylboronic acids as the substrates, red-lightinduced nPr-DMQA+-catalyzed aerobic oxidative hydroxylation proceeded smoothly as well. The successful applications of 3 in these red-light-mediated reactions have established its role as a versatile organic PC, which can serve as a complementary option for current white, blue or green-light-mediated photocatalysis. Further investigations on the applications of 3 towards more challenging photoredox catalysis are in progress.

Stereo- and regioselective construction of poly-heterocycles, especially those with several contiguous stereocenters, is still a challenge. In this paper, catalyst-dependent stereodivergent and regioselective synthesis of indole-fused heterocycles through formal cycloadditions of indolyl-allenes has been developed. The reaction features total reversion of an all-carbon quaternary stereocenter when a gold or platinum complex was employed as the catalyst through [3 + 2] cycloaddition of allene with indole, affording different diazabenzo[a]cyclopenta[cd]azulenes as epimers, respectively. In addition, in the presence of IPrAuCl and AgNTf2, highly regioselective exo-type [2 + 2] cycloaddition was observed, in which allene served as a 2C synthon. This methodology provides a simple and straightforward approach for the construction of indole-fused tricyclic systems under mild conditions in an atom-economical way.

A novel asymmetric formal [3+2] cycloaddition of vinyl cyclopropanes and isatins in the presence of Pd2(dba)3 and the chiral imidazoline-phosphine ligand (aS,R,R)-L3 has been developed, affording the corresponding highly functionalized oxindole-fused spirotetrahydrofuran frameworks in good yields along with good diastereo- and high enantioselectivities under mild conditions.

The quantitative multiplexing capacity of isobaric Tandem Mass Tags (TMT) has increased the throughput of affinity purification mass spectrometry (AP-MS) to characterize protein interaction networks of immunoprecipitated bait proteins. However, variable bait levels between replicates can convolute interactor identification. We compared the Student's t-test and Pearson's R correlation as methods to generate t-statistics and assessed the significance of interactors following TMT-AP-MS. Using a simple linear model of protein recovery in immunoprecipitates to simulate reporter ion ratio distributions, we found that correlation-derived t-statistics protect against bait variance while robustly controlling Type I errors (false positives). We experimentally determined the performance of these two approaches for determining t-statistics under two experimental conditions: irreversible prey association to the Hsp40 mutant DNAJB8 H31Q followed by stringent washing, and reversible association to 14-3-3z with gentle washing. Correlation-derived t-statistics performed at least as well as Student's t-statistics for each sample, and with substantial improvement in performance for experiments with high bait level variance. Deliberately varying bait levels over a large range fails to improve selectivity but does increase robustness between runs. The use of correlation-derived t-statistics should improve identification of interactors using TMT-AP-MS. Data are available via ProteomeXchange with identifier PXD016613.

Palladium-catalyzed asymmetric formal [3+2] cycloaddition of vinyl cyclopropanes and β,γ-unsaturated α-keto esters proceeded smoothly in the presence of chiral imidazoline−phosphine ligands to give the corresponding highly functionalized cyclopentanes in good yields along with high diastereo-and enantioselectivities under mild conditions.