Modular in-plate synthesis of N-heterocycles for direct-to-biology screening.

Rapid functional discovery increasingly demands synthetic methods that are compatible with automation, high-throughput experimentation, and minimal operational complexity. Miniaturized parallel synthesis in multi-well microplates provides a compelling alternative to traditional combinatorial approaches, enabling streamlined workflows and direct biological testing of crude products without purification. However, synthetic strategies suitable for such direct-to-biology applications remain largely confined to a narrow set of crosslinking reactions, limiting access to complex, three-dimensional scaffolds central to drug discovery. Herein, we report a highly efficient and broadly applicable multicomponent cyclocondensation that enables the rapid, modular construction of multisubstituted 6-membered tetrahydrotriazine scaffolds from readily available aldehydes, amines, and hydrazines through simple mixing at room temperature. The reaction proceeds cleanly under mild conditions and is fully compatible with plate-based synthesis, allowing high-purity compound libraries to be generated and evaluated directly upon solvent removal. Using this "mixing-drying-biotesting" workflow, we rapidly constructed and screened pilot 1,3,5-tri-substituted tetrahydrotriazine libraries with diverse structures, leading to the identification of potent α1A-adrenoceptor antagonists. Together, this work demonstrates how the integration of novel synthetic chemistry with direct-to-biology screening can unlock previously unexplored heterocyclic chemical space and accelerate early-stage drug discovery, while reducing the time, cost, and experimental waste.