Staudinger reaction, intermediates

Goldwhite, H., Gysegem, P., Schow, S., Swyke, C. Structure and decomposition of a Staudinger reaction intermediate [1-methyl(or phenyl)-... 

Early in the last century, the Nobel Prize winning chemist Hermann Staudinger discovered a reaction between phosphines and azides, which became known as the Staudinger reaction (Staudinger and Meyer, 1919). Triphenylphosphine reacts with azides to form an intermediate iminophosphorane with the release of nitrogen gas. This intermediate quickly breaks down in aqueous environments to yield triphenylphosphine oxide and a primary amine (Figure 17.17). 

Imidazoles are synthesized from A-(2-azidoethyl)phthalimide (136) via the Staudinger reaction to obtain an initial intermediate iminophosphorane 137, which is then converted by an intramolecular aza-Wittig reaction and... 

Methyl 6-amino-6-deoxy-a-D-glucopyranoside derivatives 2c were synthesized in our laboratory by a somewhat different procedure [31]. 6-0-Sulfonyl or 6-bromo-6-deoxy derivatives of methyl a-o-glucopyranoside were substituted at C-6 by sodium azide. The 6-azido-6-deoxy intermediate was then treated by acyl chlorides in the presence of triphenylphosphine (Staudinger reaction) to afford amido derivatives which were finally de-O-acetylated to give 2c. The same reaction pathway allowed the preparation of 6-alkylamido-6-deoxy-D-glucopy-ranose derivatives, starting from o-glucose [31]. 

Azetidinones on a solid support 49 have been prepared in high yield by Staudinger reaction of a supported imine with an acid chloride in the presence of a base. The liberated p-lactams were of high purity <99TL1249>. Cycloaddition of a ketene intermediate, derived fi"om an azo compound, to an imine having an oxidatively cleavable chiral auxiliary N-substituent was used to obtain p-lactams 50. The trans. cis ratio which varied between 69 31 and 93 7, depended on the nature of the substituents R and R <99S650>. 

As we have indicated previously, the reaction between ketenes and (V-silyl imines was described by Pannunzio et al. [30-33] and constitutes an interesting version of the Staudinger reaction between ketenes and imines because of the isolation of the intermediate of silyloxyazadienes. Given its interest, this reaction has been studied by different groups [92-94],... 

Staudinger reaction with a number of azides, including substituted benzoyl azidesFrom his studies, he derived a mechanism in which the two reacting molecules pass through two transition states of the composition R3PN3R, separated by the sometimes isolable intermediate mentioned above ... 

In the first step, the triphenylphosphine reacts with an alkyl azide to form an iminophosphorane with loss of nitrogen Staudinger reaction). In the second step, the nucleophilic nitrogen of the iminophosphorane attacks the carbonyl group to form a four-membered intermediate (oxazaphosphetane) from which the product Schiff base and the byproduct triphenylphosphine oxide are released. 

The Staudinger reaction is a mild method for the conversion of azides to amines by treating the azide with triphenylphosphine in the presence of water. The water is necessary, because the intermediate iminophosphrane is hydrolyzed to form the amine and triphenylphosphine oxide. Reviews (a) Gololobov, Y. G. Kasukhin, L. E Tetrahedron 1992, 48, 1353-1406. (b) Gololobov, Y. G. Zinnurova. 1. N. Kasukhin, L. E Tetrahedron 1981, 37,437 72. 

The Staudinger reaction, i.e. the [2+2] ketene-imine cycloaddition, is the most frequently employed procedure of synthesis of the azetidin-2-one nucleus. Base-promoted cyclization of suitable linear substrates is another frequently employed procedure. We wish to report the electrochemical methodologies of synthesis of P-lactams, according to both procedures, and the possible utilization of RTILs (as solvents and/or as parent of intermediates). 

Another well established reaction in solution-phase chemistry using a nucleophilic phosphane is the Staudinger reaction. A polystyrene-supported alternative proved to be less efficient, however. The hydrolysis of the intermediate imino-... 

Aminopyridazines can be obtained in a general transformation in high yields either from azidopyridazines or tetrazolo[l,5-b]pyridazines with triphenylphosphine (Staudinger reaction). The intermediate phosphazenes can be hydrolyzed according to three methods (89S666). 

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