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cycloaddition wikipedia jump to content main menu main menu move to sidebar hide navigation main page contents current events random article about wikipedia contact us contribute help learn to edit community portal recent changes upload file special pages search search appearance donate create account log in personal tools donate create account log in contents move to sidebar hide top 1 thermal cycloadditions and their stereochemistry 2 photochemical cycloadditions and their stereochemistry 3 types of cycloaddition toggle types of cycloaddition subsection 3 1 diels alder reactions 3 2 huisgen cycloadditions 3 3 nitrone olefin cycloaddition 3 4 cheletropic reactions 4 other 5 formal cycloadditions toggle formal cycloadditions subsection 5 1 iron catalyzed 2 2 olefin cycloaddition 6 references toggle the table of contents cycloaddition 23 languages العربية català čeština dansk deutsch español euskara فارسی suomi français bahasa indonesia italiano 日本語 nederlands norsk bokmål polski português română русский simple english svenska українська 中文 edit links article talk english read edit view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikimedia commons wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia chemical reaction which forms a cyclic molecule non ionic cycloadditions in organic chemistry a cycloaddition is a chemical reaction in which two or more unsaturated molecules or parts of the same molecule combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity the resulting reaction is a cyclization reaction many but not all cycloadditions are concerted and thus pericyclic 1 nonconcerted cycloadditions are not pericyclic 2 as a class of addition reaction cycloadditions permit carbon carbon bond formation without the use of a nucleophile or electrophile cycloadditions can be described using two systems of notation an older but still common notation is based on the size of linear arrangements of atoms in the reactants it uses parentheses i j where the variables are the numbers of linear atoms in each reactant the product is a cycle of size i j in this system the standard diels alder reaction is a 4 2 cycloaddition the 1 3 dipolar cycloaddition is a 3 2 cycloaddition and cyclopropanation of a carbene with an alkene a 2 1 cycloaddition 1 a more recent iupac preferred notation introduced by woodward and hoffmann uses square brackets to indicate the number of electrons rather than carbon atoms involved in the formation of the product in the i j notation the standard diels alder reaction is a 4 2 cycloaddition while the 1 3 dipolar cycloaddition is also a 4 2 cycloaddition 1 thermal cycloadditions and their stereochemistry edit thermal cycloadditions are those cycloadditions where the reactants are in the ground electronic state they usually have 4 n 2 π electrons participating in the starting material for some integer n these reactions occur for reasons of orbital symmetry in a suprafacial suprafacial syn syn stereochemistry in most cases very few examples of antarafacial antarafacial anti anti stereochemistry reactions have also been reported there are a few examples of thermal cycloadditions which have 4 n π electrons for example the 2 2 cycloaddition these proceed in a suprafacial antarafacial sense syn anti stereochemistry such as the cycloaddition reactions of ketene and allene derivatives in which the orthogonal set of p orbitals allows the reaction to proceed via a crossed transition state 3 due to the involvement of an orthogonal orbital this is classified as a pseudopericyclic reaction to which the woodward hoffmann rules do not apply to strained alkenes like trans cycloheptene derivatives have also been reported to react in an antarafacial manner in 2 2 cycloaddition reactions doering in a personal communication to woodward reported that heptafulvalene and tetracyanoethylene can react in a suprafacial antarafacial 14 2 cycloaddition however this reaction was later found to be stepwise as it also produced the woodward hoffmann forbidden suprafacial suprafacial product under kinetic conditions 4 erden and kaufmann had previously found that the cycloaddition of heptafulvalene and n phenyltriazolinedione also gave both suprafacial antarafacial and suprafacial suprafacial products consistent with the stepwise nature of the analogous tetracyanoethylene reaction 5 photochemical cycloadditions and their stereochemistry edit cycloadditions in which 4n π electrons participate can also occur via photochemical activation here one component has an electron promoted from the homo π bonding to the lumo π antibonding orbital symmetry is then such that the reaction can proceed in a suprafacial suprafacial manner an example is the demayo reaction another example is shown below the photochemical dimerization of cinnamic acid 6 the two trans alkenes react head to tail and the isolated isomers are called truxillic acids cinnamic acid cycloaddition cycloaddition of trans 1 2 bis 4 pyridyl ethene supramolecular effects can influence these cycloadditions the cycloaddition of trans 1 2 bis 4 pyridyl ethene is directed by resorcinol in the solid state in 100 yield 7 some cycloadditions instead of π bonds operate through strained cyclopropane rings as these have significant π character for example an analog for the diels alder reaction is the quadricyclane dmad reaction in the i j cycloaddition notation i and j refer to the number of atoms involved in the cycloaddition in this notation a diels alder reaction is a 4 2 cycloaddition and a 1 3 dipolar addition such as the first step in ozonolysis is a 3 2 cycloaddition the iupac preferred notation however with i j takes electrons into account and not atoms in this notation the da reaction and the dipolar reaction both become a 4 2 cycloaddition the reaction between norbornadiene and an activated alkyne is a 2 2 2 cycloaddition types of cycloaddition edit see also category cycloadditions diels alder reactions edit the diels alder reaction is perhaps the most important and commonly taught cycloaddition reaction formally it is a 4 2 cycloaddition reaction and exists in a huge range of forms including the inverse electron demand diels alder reaction hexadehydro diels alder reaction and the related alkyne trimerisation the reaction can also be run in reverse in the retro diels alder reaction reactions involving heteroatoms are known including the aza diels alder reaction and oxo diels alder reaction huisgen cycloadditions edit the huisgen cycloaddition reaction is a 2 3 cycloaddition nitrone olefin cycloaddition edit the nitrone olefin cycloaddition is a 3 2 cycloaddition cheletropic reactions edit cheletropic reactions are a subclass of cycloadditions the key distinguishing feature of cheletropic reactions is that on one of the reagents both new bonds are being made to the same atom the classic example is the reaction of sulfur dioxide with a diene other edit other cycloaddition reactions exist 4 3 cycloadditions 6 4 cycloadditions 2 2 photocycloadditions metal centered cycloaddition and 4 4 photocycloadditions formal cycloadditions edit cycloadditions often have metal catalyzed and stepwise radical analogs however these are not strictly speaking pericyclic reactions when in a cycloaddition charged or radical intermediates are involved or when the cycloaddition result is obtained in a series of reaction steps they are sometimes called formal cycloadditions to make the distinction with true pericyclic cycloadditions one example of a formal 3 3 cycloaddition between a cyclic enone and an enamine catalyzed by n butyllithium is a stork enamine 1 2 addition cascade reaction 8 an intermolecular formal 3 3 cycloaddition between an cyclic iminium chloride and cyclopentenone iron catalyzed 2 2 olefin cycloaddition edit iron pyridine diimine catalysts contain a redox active ligand in which the central iron atom can coordinate with two simple unfunctionalized olefin double bonds the catalyst can be written as a resonance between a structure containing unpaired electrons with the central iron atom in the ii oxidation state and one in which the iron is in the 0 oxidation state this gives it the flexibility to engage in binding the double bonds as they undergo a cyclization reaction generating a cyclobutane structure via c c reductive elimination alternatively a cyclobutene structure may be produced by beta hydrogen elimination efficiency of the reaction varies substantially depending on the alkenes used but rational ligand design may permit expansion of the range of reactions that can be catalyzed 9 10 references edit 1 2 3 cycloaddition iupac compendium of chemical terminology iupac 2009 doi 10 1351 goldbook c01496 isbn 978 0 9678550 9 7 retrieved 2018 10 13 pericyclic reaction iupac compendium of chemical terminology iupac 2009 doi 10 1351 goldbook p04491 isbn 978 0 9678550 9 7 retrieved 2018 10 13 wang x and houk k n 1990 carbenoid character in transition structures for reactions of ketenes with alkenes journal of the american chemical society 112 5 pp 1754 1756 izzotti anthony gleason james 2022 06 07 do antarafacial cycloadditions occur cycloaddition of heptafulvalene with tetracyanoethylene chemistry a european journal 28 49 e202201418 doi 10 1002 chem 202201418 pmid 35671245 erden ihsan kaufmann dieter 1981 01 01 cycloadditionsreaktionen des heptafulvalens tetrahedron letters in german 22 3 215 218 doi 10 1016 0040 4039 81 80058 5 issn 0040 4039 hein sara m june 2006 an exploration of a photochemical pericyclic reaction using nmr data journal of chemical education 83 6 940 942 bibcode 2006jched 83 940h doi 10 1021 ed083p940 l r macgillivray j l reid j a ripmeester 2000 supramolecular control of reactivity in the solid state using linear molecular templates j am chem soc 122 32 7817 7818 bibcode 2000jachs 122 7817m doi 10 1021 ja001239i movassaghi mohammad bin chen 2007 stereoselective intermolecular formal 3 3 cycloaddition reaction of cyclic enamines and enones angew chem int ed 46 4 565 568 doi 10 1002 anie 200603302 pmc 3510678 pmid 17146819 jordan m hoyt valeria a schmidt aaron m tondreau paul j chirik 2015 08 28 iron catalyzed intermolecular 2 2 cycloadditions of unactivated alkenes science 349 6251 960 963 bibcode 2015sci 349 960h doi 10 1126 science aac7440 pmid 26315433 s2cid 206640239 myles w smith phil s baran 2015 08 28 as simple as 2 2 science 349 6251 925 926 bibcode 2015sci 349 925s doi 10 1126 science aac9883 pmid 26315420 s2cid 42226757 v t e basic reaction mechanisms nucleophilic substitutions unimolecular nucleophilic substitution s n 1 bimolecular nucleophilic substitution s n 2 nucleophilic internal substitution s n i nucleophilic acyl substitution s n acyl electrophilic substitutions electrophilic aromatic substitution s e ar elimination reactions e1cb elimination e i elimination addition reactions electrophilic addition a e nucleophilic addition a n free radical addition cycloaddition oxidative addition unimolecular reactions intramolecular reaction isomerization photodissociation lindemann mechanism rrkm theory electron proton transfer reactions redox harpoon reaction grotthuss mechanism marcus theory inner sphere electron transfer outer sphere electron transfer medium effects solvent effects cage effect matrix isolation related topics elementary reaction reaction dynamics reactive intermediate radical chemistry molecularity stereochemistry catalysis collision theory arrow pushing potential energy surface more o ferrall jencks plot chemical kinetics rate equation equilibrium constant rate determining step reaction coordinate energy profile chemistry transition state theory activation energy activated complex arrhenius equation eyring equation michaelis menten kinetics diffusion controlled reaction authority control databases international gnd national czech republic retrieved from https en wikipedia org w index php title cycloaddition oldid 1360644603 categories cycloadditions reaction mechanisms ring forming reactions hidden categories articles with short description short description is different from wikidata cs1 german language sources de this page was last edited on 22 june 2026 at 19 13 utc page was rendered with parsoid text is available under the creative commons attribution sharealike 4 0 license additional terms may apply by using this site you agree to the terms of use and privacy policy wikipedia is a registered trademark of the wikimedia foundation inc a non profit organization privacy policy about wikipedia disclaimers contact wikipedia legal safety contacts code of conduct developers statistics cookie statement mobile view search search toggle the table of 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