📖 Multi-Component Organic Synthesis - Roll of ZnCl2 and CaCl2. Importance of Biginelli Reaction.

Multicomponent synthesis has attracted great attention due to its selectivity, synthetic convergency and atom economy in the area of drug discovery, material science and synthetic chemistry. The most common MCRs are - Mannich Reaction, Hantzsch Reaction, Biginelli Reaction, Ugi Reaction, Strecker Reaction, Passerini Reaction, Prins Reaction, Gewald Reaction. The pyrimidine derivatives such as cytosine, uracil and thymine are present in DNA and RNA which was synthesised by Biginelli Reaction. A multicomponent reaction of an aldehyde, ?-keto ester, and urea in the presence of Bronsted acid, Lewis acid or Lewisbase catalysts forming dihydropyrimidine. In Biginelli chemistry Lewis acids halides, triflates and other salts of Li, Bi, Fe, Cu, Zn, Ru, Rh, W, Mo, Mg, Co, Ni, Sb, Yb, La, Zr, Ce, Sm, Sc, V, Cd, Al, Ag, Nd, Ca, I, B, Sr, Si, Nd, Nb, K, Na, Ga, Pb, Sn etc. (sometimes even repeatedly in different journals) have been employed to achieve excellent yields and reduce reaction time. Zinc chloride was an important Lewis acid catalyst while calcium chloride is used as Lewis acid or Lewis base catalyst depending on the role ion as catalyst.