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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.
Cyclopropanation is also stereospecific as the addition of carbene and carbenoids to alkenes is a form of a cheletropic reaction, with the addition taking place in a syn manner. For example, dibromocarbene and cis -2-butene yield cis -2,3-dimethyl-1,1-dibromocyclopropane, whereas the trans isomer exclusively yields the trans cyclopropane.
The Buchner–Curtius–Schlotterbeck reaction is the reaction of aldehydes or ketones with aliphatic diazoalkanes to form homologated ketones. [1] It was first described by Eduard Buchner and Theodor Curtius in 1885 [ 2 ] and later by Fritz Schlotterbeck in 1907. [ 3 ]
Cyclopropanation (the Bingel reaction) is another common method for functionalizing C 60. Cyclopropanation of C 60 mostly occurs at the junction of 2 hexagons due to steric factors. The first cyclopropanation was carried out by treating the β-bromomalonate with C 60 in the presence of a base. Cyclopropanation also occur readily with diazomethanes.
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Carbene cyclopropanation Carbenes add to double bonds to form cyclopropanes , [ 14 ] and, in the presence of a copper catalyst , to alkynes to give cyclopropenes . Addition reactions are commonly very fast and exothermic , and carbene generation limits reaction rate.