Synthesis of polyhydroquinolines via Hantzsch’s multicomponent reaction (MCR) involves
the use of a hygroscopic and moderately toxic ammonium salt as one of the key reactants. In our effort,
we have found urea as an effective ammonia surrogate when the MCR was performed in the presence
of sulphonic acid-functionalized Wang resin (Wang-OSO3H) as a polymeric and recoverable acidic
catalyst under green conditions. Urea is relatively less hygroscopic/toxic than the commonly used ammonium
salts used in this MCR. The methodology afforded a range of polyhydroquinolines in good
yields. Depending on the nature of reaction conditions employed, the MCR afforded Biginelli product
or 1,4-DHPs when the use of 1,3-diketone was omitted.