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The Cope rearrangement is an extensively studied organic reaction involving the [3,3] sigmatropic rearrangement of 1,5-dienes. [ 14 ] [ 15 ] [ 16 ] It was developed by Arthur C. Cope . For example, 3,4-dimethyl-1,5-hexadiene heated to 300 °C yields 2,6-octadiene.
In organic chemistry, the di-π-methane rearrangement is the photochemical rearrangement of a molecule that contains two π-systems separated by a saturated carbon atom. In the aliphatic case, this molecules is a 1,4-diene; in the aromatic case, an allyl-substituted arene. The reaction forms (respectively) an ene- or aryl-substituted cyclopropane.
In the case of hexa-1,5-diene, the rearrangement is degenerate (the product is identical to the starting material), so K = 1 by necessity. In asymmetric dienes one often needs to consider the stereochemistry, which in the case of pericyclic reactions, such as the Cope rearrangement, can be predicted with the Woodward–Hoffmann rules and ...
Electrocyclic reactions occur frequently in nature. [5] One of the most common such electrocyclizations is the biosynthesis of vitamin D 3. The first step involves a photochemically induced conrotatory ring opening of 7-dehydrocholesterol to form pre vitamin D3. A [1,7]-hydride shift then forms vitamin D 3.
The reaction is then completed either by the reformation of the carbonyl through an 1,2-rearrangement or by the formation of the epoxide. There are two possible carbonyl products: one formed by migration of R 1 (4) and the other by migration of R 2 (5). The relative yield of each possible carbonyl is determined by the migratory preferences of ...
An especially reactive diene is 1-methoxy-3-trimethylsiloxy-buta-1,3-diene, otherwise known as Danishefsky's diene. [29] It has particular synthetic utility as means of furnishing α,β–unsaturated cyclohexenone systems by elimination of the 1-methoxy substituent after deprotection of the enol silyl ether.
After a short synthesis to obtain the desired spiro-[5.4] system, Nobel laureaute E.J. Corey and co-workers employed a Barton reaction to selectively introduce an oxime in a 1,3-diaxial position to the nitrite ester. The oxime is converted to a lactam via a Beckmann rearrangement and then reduced to the natural product. [24]
[4] [5] [6] These reactions are metal-catalyzed and proceed through a metallacyclobutane intermediate. [7] It was first published by Dider Villemin in 1980 describing the synthesis of an Exaltolide precursor, [ 8 ] and later become popularized by Robert H. Grubbs and Richard R. Schrock , who shared the Nobel Prize in Chemistry , along with Yves ...