Microwave assisted synthesis of 3-benzazepin-2-ones as building blocks for 2,3-disubstituted tetrahydro-3-benzazepines

Microwave assisted condensation of primary amines with keto acids 1a–c provided directly 3,4-disubstituted 1,3-dihydro-3-benzazepin-2-ones 2. Whereas small amine size, such as NH₃ afforded high yields of secondary lactams 2a, 2d, and 2g, primary amines with larger substituents in α-position led to lower yields of 2 or even to regioisomeric indanone derivatives 4. However, subsequent alkylation of 2a, 2d, and 2g with various alkyl halides provided the corresponding N-substituted 3-benzazepin-2-ones 2 in good yields. Hydrogenation of 2 followed by BH₃ reduction led to 3-benzazepines 9. 3-Benzyl-2-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine (9c) reveals high σ₁ affinity and selectivity over σ₂ and NMDA receptors.