Staudinger ketene

Asymmetric synthesis of 3-amino (3-lactams via Staudinger ketene-imine cycloaddition reaction 98KGS1448. 

Recently, they have synthesized enantiomerically pure 1,3-thiazolidine-derived spiro-(3-lactams [111] (Scheme 37) using Staudinger ketene-imine reaction starting from optically active lV-boc-1,3- thiazolidine-2-carboxylic acid derivatives and imines, thus confirming the generality of the earlier reported 1,3-thiazolidine-derived spiro-(3-lactams. 

Palomo, C. Aizpurua, J. M. Ganboa, I. Oiarbide, M. Asymmetric Synthesis of P-Lactams by Staudinger Ketene-Imine Cycloaddition Reaction, Eur. J. Org. Chem. 1999, 3223-3235. 

Enantiomerically pure 1,3-thiazolidine-derived spiro /3-lactams 505 and 506 were stereoselectively synthesized by means of a Staudinger ketene-imine reaction in the presence of 2-chloro-l-methylpyridinium iodide (Mukaiyama s reagent) starting from optically active A -BOC-l,3-thiazolidine-2-carboxylic acid derivatives 504 and imines (Scheme 127). The reactions were stereoselective and afforded spiro-/3-lactams with a /ra r -configuration. The spiro-/3-lactams 505 and 506 were transformed into enantiomerically pure chiral monocyclic /3-lactams 507 and 508... 

The Staudinger ketene cycloaddition was utilized as the key reaction in the synthesis of a number of bakkane natural products in the laboratory of A.E. Greene. Dichloroketene was generated in situ from trichloroacetyl chloride by zinc-copper alloy in the presence of phosphorous oxychloride. The [2+2] cycloaddition between dichloroketene and 1,6-dimethylcyclohexene gave the product in high yield and excellent regio- and diastereoselectivity. The cycloadduct was successfully converted to (+)-bakkenolide A. 

Palomo, C., Aizpurua, J. M. Asymmetric synthesis of 3-amino-P-laclams via Staudinger ketene-imine cycloaddition reaction. Chem. Met. Comp. (New York) (Translation of Khim. Geterot. Soed.) 1999, 34,1222-1236. 

Palomo C, Aizpurua JM, Ganboa 1, Oiarbide M (1999) Asymmetric synthesis of P-lactams by Staudinger ketene-imine cycloaddition reaction. Eur J Org Chem 1999 3223-3235... 

Two new glucose-derived oxazolidinones have been prepared, and converted to iV-acyl derivatives of type 204 (R = Me or Piv). The dialkylboron enolates derived from 204 underwent aldol reactions to give syn-products 205, with diastereomeric ratios between 8 1 and 16 1. The same group has also made the oxazolidinone 206 from D-xylose. When this was treated with Mukaiyama s reagent (2-chloro-l-methylpyridinium iodide) in the presence of an imine, a Staudinger ketene-imine cyclization occurred to give a p-lactam such as 207, the structure of which was confirmed by X-ray crystallography, in >98% de. ... 

The Staudinger ketene cycloaddition is the nonphotochemical [2 + 2] cycloaddition of a ketene and an imine to form a P-lactam. Related ketene cycloaddition reactions include the cycloaddition of a keten with an olefin to afford a cyclobutanone, with a carbonyl to give a P-lactone, and with carbodiimides to form 4-imino P-lactams. 

The mechanism of the Staudinger ketene imine cycloaddition reaction has been the subject of much debate and has recently been reviewed. The mechanism has been studied both computationally and experimentally. Experimental evidence gathered on solution phase reactions supports a two-step mechanism, in which addition of the imine nitrogen to the ketene carbonyl group occurs to generate an intermediate zwitterion. Subsequent cyclization of the zwitterion results in formation of the key C3-C4 a-bond. 

STAUDINGER Ketene Cycloaddition Cycloaddition of ketenes to olefins. 

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