Harnessing Q-tube pressure reactor for the synthesis of novel pyrano[2,3-<i>d</i>]thiazole derivatives utilizing Mg–Al-layered double hydroxide catalyst: catalysis meets sustainability

This research introduces Mg-Al-layered double hydroxide (MgAl-LDH) as an innovative sustainable nanocatalyst for the synthesis of pyrano[2,3-<i>d</i>]thiazole derivatives, utilizing Q-tube pressure reactor technology to improve efficiency and minimize environmental effects. The MgAl-LDH catalyst and its calcined derivatives (250 °C and 450 °C) were meticulously characterized using FT-IR, XRD, and BET analysis, demonstrating that the uncalcined LDH possessed a 1.5-fold greater surface area (78 m² g^-1) and enhanced catalytic activity relative to its thermally treated variants. The incorporation of Q-tube technology facilitated swift reaction times (15 minutes) and elevated yields (84-92%) under autogenic pressure (50 psi), surpassing traditional procedures. Mechanistic investigations revealed the catalyst's dual acid-base sites, which promote Knoevenagel condensation and Michael addition cascades. MgAl-LDH exhibited exceptional recyclability across five cycles with no efficiency degradation, highlighting its sustainability. The current synthetic approach has several advantages, including a low <i>E</i>-factor (0.23), a high atom economy (96.8%), and a low process mass efficiency (1.23). This study presents an environmentally sustainable and energy-efficient approach for pharmaceutical synthesis, adhering to green chemistry principles by minimizing waste and energy consumption while offering a scalable alternative to traditional transition metal-based catalysts.