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A scheme showing ring expansion by exocyclic bond migration (A) and ring opening of a bicyclic molecule (B). Rings can be expanded by attack of the ring onto an outside group already appended to the ring (a migration/insertion), opening of a bicycle to a single larger ring, or coupling a ring closing with an expansion. [1]
The Buchner ring expansion is a two-step organic C-C bond forming reaction used to access 7-membered rings. The first step involves formation of a carbene from ethyl diazoacetate, which cyclopropanates an aromatic ring. The ring expansion occurs in the second step, with an electrocyclic reaction opening the cyclopropane ring to form the 7 ...
The Büchner ring expansion reactions utilizing diazoalkanes have proven to be synthetically useful as they can not only be used to form 5- and 6-membered rings, but also more unstable 7- and 8-membered rings. [27] The Büchner–Curtius–Schlotterbeck reaction used in one Carbon ring expansions
The Dowd–Beckwith ring-expansion reaction is an organic reaction in which a cyclic carbonyl (typically a β-keto ester) is expanded by up to 4 carbons in a free radical ring expansion reaction through an α-alkylhalo substituent. The radical initiator system is based on azobisisobutyronitrile and tributyltin hydride. [1]
First described in 1900 by chemists Siegmund Gabriel and James Colman, this rearrangement, a ring expansion, is seen to be general if there is an enolizable hydrogen on the group attached to the nitrogen, [3] since it is necessary for the nitrogen to abstract a hydrogen to form the carbanion that will close the ring. [4]
The Tiffeneau-Demjanov rearrangement (after Marc Tiffeneau and Nikolai Demjanov) is a variation of the Demjanov rearrangement, which involves both a ring expansion and the production of a ketone by using sodium nitrite and hydrogen cation. Using the Tiffeneau-Demjanov reaction is often advantageous as, while there are rearrangements possible in ...
The vinylcyclopropane rearrangement or vinylcyclopropane-cyclopentene rearrangement is a ring expansion reaction, converting a vinyl-substituted cyclopropane ring into a cyclopentene ring. [1] [2] [3] Cyclopropyl groups adjacent to vinyl groups can undergo ring expansion reactions.
Pages in category "Ring expansion rearrangements" ... Metal-catalyzed σ-bond rearrangement This page was last edited on 3 January 2025, at 01:00 (UTC). ...