Staudinger reaction mechanisms

Historically, the first reactions involving thiocarbonyl ylides involve the preparation of thiiranes and 1,3-dithiolanes from diazomethane and thiocarbonyl compounds reported early in the last century by Staudinger and co-workers (12,13). Similar reactions have been smdied by Schonberg and co-workers (14—16) during the 1960s, but neither was the reaction mechanism understood nor have thiocarbonyl ylides been recognized as key intermediates. [For some remarks to this subject see (8) and (10) in (17).]... 

Scheme 31 Mechanism of the Staudinger reaction starting from ketenes generated from a-diazoketones under microwave and photoirradiation conditions...

In order to investigate the mechanism of the Staudinger reactions studied experimentally, the energy profiles for the formation of the cis and trans (3-lactams were calculated. Theoretical results suggested that the reaction would proceed most favorably with the BF3 catalyst coordinated to the ketene. 

We and others have demonstrated facile synthesis of a number of new anticancer active p-lactams. The p-lactam derivatives described herein are unique, and they demonstrate reasonable in vitro antitumor cytotoxicity. The stereochemical outcome of the Staudinger reaction as reported herein may offer our laboratory and others many additional opportunities to use p-lactams in the synthesis of biologically active compounds. Although the mechanism of action of the lead compounds has not been totally established, our research on cell cycle analysis offers intriguing... 

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 ... 

Alonso, E., del Pozo, C., Gonzalez, J. Staudinger reactions of unsymmetrical cyclic ketenes a synthetically useful approach to spiro p-lactams and derivatives. Reaction mechanism and theoretical studies. J. Chem. Soc., Perkin Trans. 1 2002, 571-576. 

Tian, W. Q., Wang, Y. A. Mechanisms of Staudinger Reactions within Density Functional Theory. J. Org. Chem. 2004, 69, 4299-4308. 

Two other procedures for the synthesis of phosphoranimines have been described, which are totally different from the Staudinger approach. Microwave irradiation of a mixture of l-aryl-4-ethoxycarbonyl-5-amino-l,2,3-triazoles(10), PPh3 and EtsN in C2CI6 provides the corresponding 5-phosphoraniminato derivatives (11) in excellent yields. A chiral A-phosphine substituted phos-phoranimine (13) has been prepared by deprotonation of cyclopropyl(triphenyl)phosphonium bromide (12) with NaNH2 via a complicated reaction mechanism. ... 

The understanding of the mechanism of the Staudinger reaction (Scheme 16.3) [84] is still a not completely resolved problem [85-89]. 

Fig. 16.2 l,3-Dialkylimidazol-2-ylidene as catalyst in the Staudinger reaction a possible mechanism (Reprinted from Ref. [96] with kind permission of The American Chemical Society)... 

Cossio FP, Arrieta A, Sierra MA (2008) The mechanism of the ketene-imine (Staudinger) reaction in its centennial stiU an unsolved problem Accounts Chem Res 8 925-936... 

If the Staudinger reaction of an alkyl azide containing a pendant carbonyl group is heated under anhydrous conditions, the iminophosphorane can nucleophilically attack the carbonyl leading to cyclic imines (via the aza-Wittig mechanism) and liberate phosphine oxide as shown below. The reaction also works intermolecularly. 

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