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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 Buchner ring expansion is encouraged to open to the desired product by placing electron withdrawing groups on the carbon added. In order to perform the ring opening on saturated bicyclic molecules the cyclopropane must be introduced such that a neighboring group can facilitate the expansion or the ring must be opened by attackate the ...
Initial steps in the Buchner–Curtius–Schlotterbeck reaction mechanism. 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 ...
Pages in category "Ring expansion reactions" The following 6 pages are in this category, out of 6 total. ... Buchner ring expansion; D. Dowd–Beckwith ring-expansion ...
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The migration occurs with full retention of configuration at the R-group. The migratory aptitude of the R-group is roughly tertiary > secondary ~ aryl > primary. The isocyanate formed can then be hydrolyzed to give a primary amine , or undergo nucleophilic attack with alcohols and amines to form carbamates and urea derivatives respectively.
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In the case of arenes, the cyclopropanation product undergoes further electrocyclic ring opening to give cycloheptatriene products (Buchner ring expansion). [2] Alkenes undergo both C=C methylenation and C–H methylenation insertion to give a mixture of cyclopropanation and homologation products.