text: Regular achiral organocatalysts are based on nitrogen such as piperidine used in the Knoevenagel condensation.  DMAP used in esterifications and DABCO used in the Baylis-Hillman reaction. Thiazolium salts are employed in the Stetter reaction. These catalysts and reactions have a long history but current interest in organocatalysis is focused on asymmetric catalysis with chiral catalysts, called asymmetric organocatalysis or enantioselective organocatalysis. A pioneering reaction developed in the 1970s is called the Hajos–Parrish–Eder–Sauer–Wiechert reaction. Between 1968 and 1997, there were only a few reports of the use of small organic molecules as catalysts for asymmetric reactions (the Hajos–Parrish reaction probably being the most famous), but these chemical studies were viewed more as unique chemical reactions than as integral parts of a larger, interconnected field.
  In this reaction, naturally occurring chiral proline is the chiral catalyst in an Aldol reaction. The starting material is an achiral triketone and it requires just 3% of proline to obtain the reaction product, a ketol in 93% enantiomeric excess. This is the first example of an amino acid-catalyzed asymmetric aldol reaction.
  The asymmetric synthesis of the Wieland-Miescher ketone (1985) is also based on proline and another early application was one of the transformations in the total synthesis of Erythromycin by Robert B. Woodward (1981). A mini-review digest article focuses on selected recent examples of total synthesis of natural and pharmaceutical products using organocatalytic reactions.
  Many chiral organocatalysts are an adaptation of chiral ligands (which together with a metal center also catalyze asymmetric reactions) and both concepts overlap to some degree.
  A breakthrough in the field of organocatalysis came in 1997 when Yian Shi reported the first general, highly enantioselective organocatalytic reaction with the catalytic asymmetric epoxidation of trans- and trisubstituted olefins with chiral dioxiranes. Since that time, several different types of reactions have been developed.