Cyclopropanes
Cyclopropanes are a family of organic compounds containing the cyclopropyl group. The parent is cyclopropane ({{chem2|C3H6}}).
Synthesis and reactions
Most cyclopropanes are not prepared from the parent cyclopropane, which is somewhat inert.
Cyclopropyl groups are often prepared by cyclization of 1,3-difunctional alkanes. An example of the former, cyclopropyl cyanide is prepared by the reaction of 4-chlorobutyronitrile with a strong base.{{cite journal|last=Schlatter|first=M. J.|journal=Organic Syntheses|title=Cyclopropyl Cyanide|year=1943|volume=23|pages=20|doi=10.15227/orgsyn.023.0020}} Phenylcyclopropane is produced analogously from the 1,3-dibromide.{{cite journal |doi=10.15227/orgsyn.044.0030 |title=Cyclopropylbenzene |journal=Organic Syntheses |date=1964 |volume=44 |page=30 }}
A second major route to cyclopropanes entails addition of methylene (or its substituted derivatives) to an alkene, a process called cyclopropanation.{{cite journal |first1=Keiji|last1=Maruoka|first2=Soichi|last2=Sakane|first3=Hisashi|last3=Yamamoto|doi=10.15227/orgsyn.067.0176 |title=Selective Cyclopropanation of (S)-(−)-Perillyl Alcohol: 1-Hydroxymethyl-4-(1-Methylcyclopropyl)-1-Cyclohexene |journal=Organic Syntheses |date=1989 |volume=67 |page=176 }}
Substituted cyclopropanes undergo the reactions associated with the cyclopropyl ring or the substituents. Vinylcyclopropanes are a special case as they undergo vinylcyclopropane rearrangement.
Applications and occurrence
File:(R,R)-(+)-trans-chrysanthemic acid.svg.]]
Cyclopropane derivatives are numerous.{{cite book |doi=10.1002/0470023481|title=The Chemistry of the Cyclopropyl Group|series=The Chemistry of Functional Groups|year=1995|volume=2|isbn=0471940747|editor1-last=Rappoport|editor1-first=Zvi}} Many biomolecules and pharmaceutical drugs feature the cyclopropane ring. Famous example is aminocyclopropane carboxylic acid, which is the precursor to ethylene, a plant hormone.{{Cite journal|last1=Kieber|first1=Joseph J.|last2=Schaller|first2=G. Eric|date=2019-07-01|title=Behind the Screen: How a Simple Seedling Response Helped Unravel Ethylene Signaling in Plants|url=https://doi.org/10.1105/tpc.19.00342|journal=The Plant Cell|volume=31|issue=7|pages=1402–1403|doi=10.1105/tpc.19.00342|issn=1040-4651|pmc=6635871|pmid=31068448}}
The pyrethroids are the basis of many insecticides.{{cite journal |doi=10.1002/1521-3773(20010618)40:12<2251::AID-ANIE2251>3.0.CO;2-R|title=Fascinating Natural and Artificial Cyclopropane Architectures|year=2001|last1=Faust|first1=Rüdiger|journal=Angewandte Chemie International Edition|volume=40|issue=12|pages=2251–2253|pmid=11433485}} Several cyclopropane fatty acids are known.
:file:1-aminocyclopropanecarboxylic acid 200.svg plays an important role in the biosynthesis of the plant hormone ethylene.]]
