Synthesis of Some Polysubstituted Nicotinonitriles and Derived Pyrido[2,3-d]pyrimidines as In Vitro Cytotoxic and Antimicrobial Candidates

Scheme 1

Synthesis of the target compounds 1–37. Reagents and reaction conditions: i: malononitrile, NH₄OAc, EtOH, reflux, 4-5 h; ii: HCOOH, heating, 30 min.; iii: Ac₂O, heating, 10 min.; iv: PhNCS, pyridine, reflux, 4 h; v: PhCONCS, acetone, reflux, 10 h; vi: urea, 260–300°C, 1 h; vii: thiourea, 260–300°C, 1.5 h; viii: R₂X, 1N NaOH, ethanol, r.t., 2-3 h.