Forster reaction

The third reaction type to be discussed in this section is the Forster reaction. It was discovered by Forster in 1915, as he had obtained (benzoyl)(phenyl)diazomethane (2-diazo-l,2-diphenylethan-l-one, 2.62) by treatment of (Z)- and ( )-benzil monooxime ((Z) = 2.95) with sodium hypochlorite and ammonia (which readily forms chloramine). a-Keto-monoximes like 2.95 are obtained easily from a-methylene-con-taining ketones (e.g., 2.94) by the oximation reaction, i.e., a nitrosation with a nitrous acid ester followed by a C O proton shift (2-41). 

Forster s method was ignored for many decades, until it was realized that it is useful for the synthesis of a-diazo ketones (Horner et al., 1958, 1959 Cava et al., 1958 Jung et al., 1985). 

It can be used also for the synthesis of unsubstituted diazoalkanes, e.g., for diazomethane starting from formaldehyde (Rundel, 1962), but it has no importance for such syntheses. This is also the case for the synthesis of aryldiazoalkanes such as diazophenylmethane, diazodiphenylmethane and diazofluorene (Meinwald et al., 1959). 

The application of the Forster reaction to the synthesis of a-diazo ketones is particularly important for derivatives of indanone and steroidal ketones with a methylene group in the a-position to the carbonyl function. The reaction allows functionalization of the a-methylene group. Examples include the synthesis of 2-diazo-3,3-diphenyl-indan-l-one (2-42 Cava et al., 1958) and 16-diazo-3)ff-hydro-xy-androst-5-en-17-one (2-43, Muller et al., 1962 Wheeler and Meinwald, 1988). 

Diazo Chemistry II Aliphatic, Inorganic and Organometallic Compounds. By Heinrich Zollinger Copyright 1995 VCH Verlagsgesellschail mbH ISBN 3-527-29222-5 

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Diazo esters can also be prepared from glycine esters by treatment with nitrous acid [966] or with alkyl nitrites. Further methods include the oxidation of hydrazones, oximes (Forster reaction), and semicarbazones, the base-induced... 

The present procedure for the synthesis of an a-diazo ketone is a modification of the Forster reaction,which has been recently exploited by numerous workers.The synthesis is generally applicable to cyclic ketones, is convenient, and offers moderate yields (60-70%) of pure a-diazo ketones. 

N-Nitrosation of oximes by nitrosyl halides or nitrite esters often results in the formation of N-nitrimines, R R C=NN02, these compounds being formed by rearrangement of the initial adducts. N-Amination of oximes by chloramine or by hydroxylamine-O-sulfonic acid can result in the formation of diazo compounds (Scheme 28). The reaction, known as the Forster reaction, has been used for the preparation of aryldiazoalkanes, although better methods are usually available. Diazo ketones of the general formula (49) have also been prepared by this method from the oximes. "... 

Forster reaction. Formation of secondary amines by condensation of a primary amine with an... 

Although Forster initially reported this reaction, it was Decker and Becker who investigated it in more depth and made this reaction an applicable route for the preparation of secondary amines. Therefore, this reaction is known as the Decker-Becker method or Forster reaction, but it is named the Decker-Becker secondary amine synthesis in this book. It is the synthesis of secondary amine by the condensation of primary amines with aldehydes to form an imine intermediate, which then reacts with alkyl halides via alkylation to Anally afford secondary amines after hydrolysis. This reacAon gives good results when methyl halides are used but works poorly and unstably when larger alkyl halides are applied. ... 

This reaction was initially reported by Forster in 1915. It is the synthesis of diazoketones, especially for the cyclic diazoketones from a-keto oximes by the reaction with chloramines. Therefore, it is known as the Forster reaction. Although two mechanisms have been proposed for this reaction,experimental evidence favors the one involving the attack of NH2CI by the lone-pair electrons of the oxime nitrogen. " This reaction has been modified via the generation of chloramine in situ, which is used in the preparation of 2-diazo-1 -indanones. ... 

Other references related to the Forster reaction are cited in the literature. ... 

Forster Diazoketone Synthesis Forster Reaction Four-Component Condensation Franchimont Reaction Frankland Synthesis Frankland-Duppa Reaction Freund Reaction... 

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