Staudinger-type cyclization

A series of polyoxygenated azepane derivatives 5 were created from azi-dolactol 4 via a Staudinger/aza-Wittig-type cyclization followed by reaction with -alkylmagnesium halides, en route to the synthesis of a library of potent glucosidase inhibitors (140BC8977). 

Isocyanates have provided one carbon atom in transformations of the general type (296) - (290). Thus, azide (343) reacts with triphenylphosphine in a Staudinger reaction giving phosphorane (344) which is then treated with isocyanates (RNCO R = benzyl or aryl) giving naphthyridines (346) (50-59% yield) via the carbodiimide (345). The cyclization (345)->(346) occurred in toluene at 160°C (92T4601). Azide (347) undergoes a similar sequence of reactions yielding a 1 1 mixture of isomeric naphthyridines (348) and (349) (44—47% yield). 

Using Ph3P to induce Staudinger reaction of a-azidocinnamic esters as well as Wolff rearrangement of a-diazo ketones, two types of mutually reactive molecules are formed. The natural course for aza-Wittig reaction is pursued to produce cyclization-prone ketene imines. ... 

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. ... 

On the other hand, another [2 - - 2 - - 2]-type cycloaddition of one molecule of ketenes with two molecules of imines enters in the Staudinger reaction (Scheme 123). Podlech and co-workers. (2001JCS(P1)2566) reported their practical observation of the [2 -f 2 -f 2]-cyclization, giving... 

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