Concise total syntheses of (R)-pipecolic acid, (2R,3R)-3-hydroxypipecolic acid and formal syntheses of β-(+)-conhydrine, (−)-lentiginosine, (−)-swainsonine and -1,2-di-epi-swainsonine have been accomplished starting from a common chiral synthon.

The diastereoselective formal synthesis of (−)-quinagolide, a D2 receptor agonist, has been achieved. The synthesis started from l-pyroglutamic acid and relied on utilization of (a) a stereospecific catalytic hydrogenation and diastereoselective Horner–Emmons–Michael cascade to obtain functionalized prolinate, (b) a Lewis acid mediated Pummerer cyclization to construct a tricyclic fused ring system, and (c) a diastereoselective ring expansion via a bicyclic aziridinium intermediate to access the required 3-substituted piperidine scaffold.

Photocatalysis for direct C−H trifluoromethylation represents an ideal way to synthesize trifluoromethyl‐containing chemical compounds, but the conventional batch processes are inefficient with limited light penetration and indispensably irradiated for a long while. Herein, we report a continuous‐flow protocol for photocatalytic direct C−H trifluoromethylation of heterocycles in the presence of an organic photoredox catalyst: 2,4,6‐tris(diphenylamino)‐3,5‐difluorobenzonitrile (3DPA2FBN). In this approach, benefiting from the merger of organic photoredox catalysis and continuous‐flow techniques, a variety of trifluoromethylated heterocycles were rapidly synthesized up to 85 % yield with 80 min residence time under metal‐ and oxidant‐free reaction conditions.

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