In organic chemistry, the Soai reaction is the

alkylation Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting ...

of pyrimidine-5-carbaldehyde with

diisopropylzinc Diisopropylzinc is an organozinc compound with the chemical formula ZnC6H14. It is the key reagent in the Soai reaction, which is both autocatalytic and enantiospecific. This chemical is pyrophoric A substance is pyrophoric (from grc-gre, � ...

. The reaction is

autocatalytic A single chemical reaction is said to be autocatalytic if one of the reaction products is also a catalyst for the same or a coupled reaction.Steinfeld J.I., Francisco J.S. and Hase W.L. ''Chemical Kinetics and Dynamics'' (2nd ed., Prentice-Hall 199 ...

and leads to rapidly increasing amounts of the same

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...

of the product. The product pyrimidyl alcohol is chiral and induces that same chirality in further catalytic cycles. Starting with a low

enantiomeric excess In stereochemistry, enantiomeric excess (ee) is a measurement of purity used for chiral substances. It reflects the degree to which a sample contains one enantiomer in greater amounts than the other. A racemic mixture has an ee of 0%, while a sin ...

produces a product with very high enantiomeric excess. The reaction has been studied for clues about the origin of

homochirality Homochirality is a uniformity of chirality, or handedness. Objects are chiral when they cannot be superposed on their mirror images. For example, the left and right hands of a human are approximately mirror images of each other but are not their ow ...

among certain classes of

biomolecule A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include large ...

s. :

The Japanese chemist Kensō Soai (1950–) discovered the reaction in 1995. For his work in "elucidating the origins of chirality and homochirality", Soai received the

Chemical Society of Japan The (CSJ) is a learned society and professional association founded in 1878 in order to advance research in chemistry. The mission of the CSJ is to promote chemistry for science and industry in collaboration with other domestic and global societ ...

award in 2010. Other chiral additives can be used as the initial source of

asymmetric induction In stereochemistry, asymmetric induction (also enantioinduction) describes the preferential formation in a chemical reaction of one enantiomer or diastereoisomer over the other as a result of the influence of a chiral feature present in the sub ...

, with the major product of that first reaction being rapidly amplified. For example, Soai's group has demonstrated that even chiral

quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

hydrocarbons, which have no clear Lewis basic site for binding the nucleophile, are nonetheless capable of inducing asymmetric catalysis in the reaction. : Cryptochiral asymmetric autocatalysis in Soai reaction

Cryptochiral asymmetric autocatalysis in Soai reaction

The chiral induction is believed to occur as a result of interactions between the C–H bonds of the alkane and the

pi electron In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals ...

s of the aldehyde. In another example, Soai and coworkers showed that even sup>15N''2R'', 3''S'')-bis(dimethylamino)butane, whose chirality results solely due to the difference between ¹⁴N and ¹⁵N (7% isotopic mass difference), gave 45% ee when used as a stoichiometric ligand.

References

Further reading