Long-term ambient air-stable cubic CsPbBr3 perovskite quantum dots using molecular bromine

We report unprecedented phase stability of cubic CsPbBr3 quantum dots in ambient air obtained by using Br2 as halide precursor. Mechanistic investigation reveals the decisive role of temperature-controlled in situ generated, oleylammonium halide species from molecular halogen and amine for the long term stability and emission tunability of CsPbX3 (X = Br, I) nanocrystals

Skeletal Transformation of Unactivated Arenes Enabled by a Low-Temperature Dearomative (3+2) Cycloaddition

Simple aromatic compounds like benzene are abundant feedstocks, for which the preparation of derivatives chiefly begins with electrophilic substitution reactions, or less frequently reductions. Their high stability makes them particularly reluctant to participate in cycloadditions under ordinary reaction conditions. Here we demonstrate the exceptional ability of 1,3-diaza-2-azoniaallene cations to undergo formal (3+2) cycloadditions with unactivated benzene derivatives, below room temperature, to provide thermally stable dearomatized adducts on a multi-gram scale. The cycloaddition, which tolerates polar functional groups, activates the ring toward further elaboration. On treatment with dienophiles the cycloadducts undergo a (4+2) cycloaddition-cycloreversion cascade to yield substituted or fused arenes, including naphthalene derivatives. The overall sequence results in the transmutation of arenes through an exchange of the ring\u27s carbons: a two-carbon fragment from the original aromatic ring is replaced with another from the incoming dienophile, introducing an unconventional disconnection for the synthesis of ubiquitous aromatic building blocks. Applications of this two-step sequence to the preparation of substituted acenes, isotopically labeled molecules, and medicinally relevant compounds are demonstrated

Stereospecific Synthesis of 1,4,5,6-Tetrahydro­pyrimidines via Domino Ring-Opening Cyclization of Activated Aziridines with α‑Acidic Isocyanides

An expeditious synthetic route to access structurally diverse 1,4,5,6-tetrahydro­pyrimidines via domino ring-opening cyclization of activated aziridines with α-acidic isocyanides has been established. The transformation proceeds via Lewis acid mediated S_N2-type ring opening of activated aziridines with α-carbanion of the isocyanides followed by a concomitant 6-<i>endo</i>-<i>dig</i> cyclization in a domino fashion to furnish the 1,4,5,6-tetrahydro­pyrimidine derivatives in excellent yields (up to 84%) and also in diastereo- and enantiomerically pure form (dr >99:1, ee >99%)

Syntheses of Tetrahydrobenzo­azepino­indoles and Dihydro­benzo­diazepino­indoles via Ring-Opening Cyclization of Activated Aziridines with 2‑(2-Bromo­phenyl)‑1<i>H</i>‑indoles

Two efficient, modular, step- and pot-economic strategies to access various 5,6,7,12-tetrahydro­benzo­[2,3]­azepino­[4,5-<i>b</i>]­indoles and 6,7-dihydro-5<i>H</i>-benzo­[5,6]­[1,4]­diazepino­[1,7-<i>a</i>]­indoles are disclosed that advance via S_N2-type regioselective ring opening of enantiopure aziridines with 2-(2-bromophenyl)-1<i>H</i>-indoles at their C3 and indolyl N centers, respectively, followed by Cu-mediated C–N cyclization which furnishes the products in excellent yields with outstanding enantiomeric excesses (up to >99%)

Syntheses of Tetrahydrobenzo­azepino­indoles and Dihydro­benzo­diazepino­indoles via Ring-Opening Cyclization of Activated Aziridines with 2‑(2-Bromo­phenyl)‑1<i>H</i>‑indoles

Two efficient, modular, step- and pot-economic strategies to access various 5,6,7,12-tetrahydro­benzo­[2,3]­azepino­[4,5-<i>b</i>]­indoles and 6,7-dihydro-5<i>H</i>-benzo­[5,6]­[1,4]­diazepino­[1,7-<i>a</i>]­indoles are disclosed that advance via S_N2-type regioselective ring opening of enantiopure aziridines with 2-(2-bromophenyl)-1<i>H</i>-indoles at their C3 and indolyl N centers, respectively, followed by Cu-mediated C–N cyclization which furnishes the products in excellent yields with outstanding enantiomeric excesses (up to >99%)

Syntheses of Tetrahydrobenzo­azepino­indoles and Dihydro­benzo­diazepino­indoles via Ring-Opening Cyclization of Activated Aziridines with 2‑(2-Bromo­phenyl)‑1<i>H</i>‑indoles

Two efficient, modular, step- and pot-economic strategies to access various 5,6,7,12-tetrahydro­benzo­[2,3]­azepino­[4,5-<i>b</i>]­indoles and 6,7-dihydro-5<i>H</i>-benzo­[5,6]­[1,4]­diazepino­[1,7-<i>a</i>]­indoles are disclosed that advance via S_N2-type regioselective ring opening of enantiopure aziridines with 2-(2-bromophenyl)-1<i>H</i>-indoles at their C3 and indolyl N centers, respectively, followed by Cu-mediated C–N cyclization which furnishes the products in excellent yields with outstanding enantiomeric excesses (up to >99%)

Stable lead-halide perovskite quantum dots as efficient visible light photocatalysts for organic transformations

International audienceLead halide perovskite (LHP) based colloidal quantum dots (CQDs) have tremendous potential for photocatalysis due to their exceptional optical properties. However, their applicability in catalysis is restricted due to poor chemical stability and low recyclability. We report halide-passivated, monodisperse CsPbBr3CQDs as a stable and efficient visible-light photocatalyst for organic transformations. We demonstrate oxidative aromatization of a wide range of heterocyclic substrates including examples which are poor hydrogen transfer (HAT) reagents. Two to five-fold higher rate kinetics were observed for reactions catalyzed by CsPbBr3CQDs in comparison with bulk-type CsPbBr3 (PNCs) or conventionally synthesized CsPbBr3CQDs and other metal organic dyes (rhodamine 6G and [Ru(bpy)3]2+). Furthermore, these CQDs exhibit improved air-tolerance and photostability and in turn show a higher turnover number (TON) of 200, compared to conventionally prepared CQDs (TON = 166) and state-of-the-art bulk-type perovskite-based catalyst (TON = 177). Our study paves the way for the practical applicability of energy-level tunable, size-controlled LHP CQDs as efficient photocatalysts in organic synthesis