Staudinger protocol

The isolation of phosphazides has also been reported for Staudinger reactions of R3P (R = Me, Et, Ph) with azido-p-benzoquinonedibenzenesulfonimines. Enantioseparations have been carried by application of the Staudinger protocol. An interesting tripodal ligand system (5) has been prepared by the reaction of bis-2,6-diphenylphosphanyl pyridine with azides. Complexation of equimolar amounts of [MCl2(thf)2] (M = Co, Fe) with (5b) in thf leads to the formation of the complex (6) and (7), respectively. 

The group of Podlech has reported that trans-substituted (3-lactams (dr 70 30) can be prepared treating an Fmoc-protected leucine-derived diazoketone with a benzylidene-protected glycine ester in a photochemically induced Staudinger-type reaction [173]. Separation of the isomers, deprotection, and attachment of Fmoc-proline using the pentafluorphenyl ester activation protocol yielded the protected peptidomimetic in 93% yield, (Scheme 74). Deprotection and amidation resulted in formation of the /ram-substituted (3-lactam. 

A new protocol for the stereoselective synthesis of (i-lactams [213] has been reported to be performed by a conrotatory ring closure of l-halo-3-aza-4-alkyl-l, 3-dienes, previously prepared by Staudinger methodology, (for the synthesis and chemistry of /V-silyl imines see [214] for [2+2] cycloaddition of /V-silyl imines and ketenes see [215]) in refluxing toluene (Scheme 96). 

The multi-step preparations of pyrazoloisoquinolines, benzodiazepines and benzothiadiazepines" also occur via a Staudinger and intramolecular aza-Wittig protocol. 

One of the reasons that the Staudinger reduction is such a powerful synthetic tool is the fact that azides can be introduced into a molecule fairly easily.1-2 In fact, some of the improvements to the Staudinger reduction over the years have included many one-pot protocols converting alkyl bromides, alkyl chlorides, alcohols, and acetates to azides followed by the in situ reduction to the corresponding amines using the Staudinger reaction. 

Experimental protocol for Staudinger-Bertozzi, Cu(l)-catalyzed Huisgen alkyne-azide cycloaddition, and reverse-electron-demand Diels-Alder ligation to distinguish between pi, p2,and p5. 

The intramolecular version of the tandem Staudinger/aza-Wittig reaction is often referred to as Eguchi aza-Wittig protocol (cf. references 14f, 60, 119-120, etc.)... 

The Staudinger synthesis of a PI phosphazene is a simple modification of the above protocol, where triphenylphosphine is substituted with a triaminophosphine—a... 

Thus, Basso and coworkers reported the synthesis of a small library of novel class of oxazolines in two steps, following a Passerini-Zhu/Staudinger-aza-Wittig (SAW) protocol (Scheme 8.23) [55]. Interestingly, alcohols 65 are used instead of the corresponding aldehydes and they are oxidized in the medium following the aforementioned protocol reported by Zhu s group [22]. 

SCHEME 8.23 Passerini-Zhu/Staudinger-aza-Wittig protocol (a) IBX, THF, MW (150W), 100°C (b) polymer supported triphenylphos-... 

F. de Moliner, S. Crosignani, L. Banfi, R. Riva, A. Basso, J. Comb. Chem. 2010, 12, 613-616. Synthesis of 5-carbox-amide-oxazolines with a Passerini-Zhu/Staudinger-aza-Wittig two-step protocol. 

Here is what one could call a pretty honest protocol of one of my morning working sessions with Hermann Staudinger in those days (1956) ... 

In 2013, Hackenberger and coworkers [66], in Berlin, reported the cycloaddition of a borane-protected alkyne-phosphonite with azides to form borane-protected triazole-phosphonites (Scheme 9.24). In this reaction protocol, we have a sequence of two different couplings with two different azido reagents in the first, we have a CuAAC cycloaddition, followed by a metal-free Staudinger phosphonite reaction. 

Quinazoline alkaloids containing the indole skeleton such as tryptanthrin (156) have been constructed via intramolecular aza-Wittig reaction of amide derivatives (Scheme 15.35). The fused quinazoline ring in tryptanthrin (156) could be synthesized efficiently in a one-pot procedure via the consecutive Staudinger/intramolecular aza-Wittig reaction of the corresponding azide 154 with tributylphosphine (Eguchi protocol). 

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