Recent applications of thiourea-based organocatalysts in asymmetric multicomponent reactions (AMCRs)

One-pot multiple bond-forming reactions under metal-free conditions have tremendous potential in organic and medicinal chemistry considering their synthetic efficiency and eco-friendliness. In this direction, organocatalysis, i.e. application of organic molecules as catalysts, in multicomponent reactions is one of the best combinations for the preparation of complex molecules in minimum steps under green reaction conditions. Thiourea-based organic molecules show excellent catalytic activity in various transformations by their unique double H-bonding activation process. Chiral organic molecules having a thiourea backbone are well-recognized catalysts for the enantioselective synthesis of diverse products from asymmetric two- or multicomponent reactions. Simultaneous dual activation of the electrophile and the nucleophile in an MCR by using bifunctional thiourea-based chiral organocatalysts has gained considerable interest in recent times. Although several review articles are available in the literature on organocatalysis, asymmetric domino reactions, or multicomponent reactions using various organocatalysts, however, to date there has been no dedicated review article on this emerging topic, i.e. asymmetric multicomponent reactions catalysed by thiourea-based organocatalysts. Thus, this review aims to highlight the recent applications of thiourea-based organocatalysts in asymmetric multicomponent reactions.