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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 ...
Ethyl diazoacetate (N=N=CHC(O)OC 2 H 5) is a diazo compound and a reagent in organic chemistry. It was discovered by Theodor Curtius in 1883. [4] The compound can be prepared by reaction of the ethyl ester of glycine with sodium nitrite and sodium acetate in water. As a carbene precursor, it is used in the cyclopropanation of alkenes.
In organic chemistry, the Roskamp reaction is a name reaction describing the reaction between α-diazoesters (such as ethyl diazoacetate) and aldehydes to form β-ketoesters, often utilizing various Lewis acids (such as BF 3, SnCl 2, and GeCl 2) as catalysts. [1] [2] [3] The reaction is notable for its mild reaction conditions and selectivity.
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 ]
This reaction is also called the Regitz diazo transfer. [7] Examples are the synthesis of tert-butyl diazoacetate [8] and diazomalonate. [9] Methyl phenyldiazoacetate is generated in this way by treating methyl phenylacetate with p-acetamidobenzenesulfonyl azide in the presence of base. [10] [11]
The periselectivity of a particular reaction depends on the structure of both the ketene and the substrate. Although the reaction is predominantly used to form four-membered rings, a limited number of substrates undergo [3+2] or [4+2] reactions with ketenes. Examples of all three modes of cycloaddition are discussed in this section.
1,3 dipolar cycloadditions have been developed as a bioorthogonal reaction using a nitrile oxide as a 1,3-dipole and a norbornene as a dipolarophile. Its primary use has been in labeling DNA and RNA in automated oligonucleotide synthesizers, [31] and polymer crosslinking in the presence of living cells. [32]
Enone–alkene cycloadditions often suffer from side reactions, e.g. those associated with the diradical intermediate. These side reactions can often be minimized by a judicious choice of reaction conditions. Dissolved oxygen is avoided since it is photoreactive. A variety of solvents can be used.