Intramolecular thermal cyclization and benzannulation reactions of the Gould–Jacobs and Conrad–Limpach types were performed in a designed continuousflow reactor system at temperatures in the range of 300–360 °C and under high pressure conditions (100–160 bar) with very short residence times (0.45–4.5 min) in tetrahydrofuran as a low-boiling point solvent. Substituted heteroaromatic compounds including
A compound of formula I,
wherein A, Ra, Rb, R1 to R5, m and t are as defined as disclosed, or a pharmaceutically acceptable salt or ester thereof, useful as an alpha-2 antagonist. The compounds I can be used for the treatment of diseases or conditions where alpha-2 antagonists are indicated to be effective.