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Cyclopropane itself is mainly of theoretical interest but many of its derivatives - cyclopropanes - are of commercial or biological significance. [3] Cyclopropane was used as a clinical inhalational anesthetic from the 1930s through the 1980s. The substance's high flammability poses a risk of fire and explosions in operating rooms due to its ...
A second major route to cyclopropanes entails addition of methylene (or its substituted derivatives) to an alkene, a process called cyclopropanation. [3] Substituted cyclopropanes undergo the reactions associated with the cyclopropyl ring or the substituents. Vinylcyclopropanes are a special case as they undergo vinylcyclopropane rearrangement.
Although cyclopropanes are relatively rare in biochemistry, many cyclopropanation pathways have been identified in nature. The most common pathways involve ring closure reactions of carbocations in terpenoids. Cyclopropane fatty acids are derived from the attack of S-adenosylmethionine (SAM) on unsaturated fatty acids.
Activation of cyclopropanes by transition metals; Acylfulvene; Adozelesin; Aliflurane; 1-Aminocyclopropane-1-carboxylic acid (+)-cis-2-Aminomethylcyclopropane carboxylic acid; Angustific acid; Angustifodilactone
Methods for the stereoselective synthesis of cyclopropanes from diazocarbonyl compounds and olefins have relied on either the use of pre-formed chiral rhodium catalysts or chiral auxiliaries on the diazocarbonyl compound. For example, Rh 2 [S-DOSP] 4 is a highly effective catalyst for the enantioselective cyclopropanation of alkenes. [9] (3)
In organometallic chemistry, the activation of cyclopropanes by transition metals is a research theme with implications for organic synthesis and homogeneous catalysis. [1] Being highly strained, cyclopropanes are prone to oxidative addition to transition metal complexes.
The specificity of these reagents allow cyclopropanes to be placed in poly-unsaturated systems that zinc-based reagents will cyclopropanate fully and unselectively. For example, i-Bu 3 Al will cyclopropanate geraniol at the 6 position, while Sm/Hg, will cyclopropanate at the 2 position, as shown below.
A wide variety of divinylcyclopropanes undergo the titular reaction. These precursors have been generated by a variety of methods, including the addition of cyclopropyl nucleophiles (salts of lithium, [8] or copper [9]) to activated double or triple bonds, elimination of bis(2-haloethyl)cyclopropanes [10] and cyclopropanation. [11]