Nitrogen ylides synthesis

A synthesis of a-( trifluoromcthyl)-a-amino esters 5 has been developed based on the [1,2] Stevens rearrangement of nitrogen ylides 4, obtained by the transition-metal-calalyzed decomposition of methyl 2-diazo-3,3,3-trifluoropropanoate (3) in the presence of tertiary amines.2... 

Another interesting use of nitrogen ylides in synthesis was reported by Williams and Miller who employed this intermediate in the preparation of a bicyclo P-lactam. P-Lactam 152 was formed in a single step from the diazo precursor 150.68 The proposed mechanism involves a Rh(II)-catalyzed generation of ammonium ylide 151 which abstracts a proton from the benzylic position and then undergoes N-0 bond heterolysis to generate the cyclized product and benzaldehyde. 

APPLICATION OF NITROGEN YLIDE CYCLIZATIONS FOR ORGANIC SYNTHESIS... 

Alternatively, an electrochemical procedure was employed in the synthesis of amino acids from nitridomolybdenum complex 4 via nitrogen-carbon and carbon-carbon bond formations involving imide 5 and nitrogen ylides 6. trans-[MoCl(N)(Ph2PCH2CH2PPh2)] 4 reacted with methyl iodoacetate to give the cationic complex 5. Complex 6 was obtained by the deprotonation of 5 at the a-carbon followed by treatment with Mel to afford the cationic methyl derivative 7. Electrochemical cleavage of the Mo-N bond of the complex 5 or 7 proceeded in the presence of acetic acid to release amino acid esters in 70-80% yield (Scheme 2) [12]. 

Beall, L. S., Padwa, A. Application of nitrogen ylide cyclizations for organic synthesis. Advances in Nitrogen Heterocycles 1998, 3, 117-158. 

Phosphorus-based olefinations continue to be the most widely used methods for the synthesis of alkenes. An understanding of most facets of the mechanism of the Wittig reaction seems to have been achieved and this has been summarised in a substantive review. Some of the principles established in these mechanistic studies can be applied to phosphorus-based olefinations other than the Wittig reaction. However, substantive mechanistic studies of phosphine oxide-based and phosphonate-based oiefinations are urgently required. A combination of the variety of phosphorus-based methods and the improved understanding of their mechanisms now aliows a substantiai degree of controi of both reactivity and stereochemistry in olefin synthesis. However, studies are required of the applications of established structure-reactivity relationships in ylides and of the various carbon and nitrogen ylide-anions recently reported. 

Insertion into C-H bond. Carbalkoxycarbenes also insert into the C-H bond of N-methylpyrrole (via nitrogen-ylides ) to yield an important intermediate in the synthesis of two drugs, tolmetin XLVI(a) and zomepirac XLVI(b) [85] (Me Neil Pharmaceuticals). 

Although nitrogen ylides have been extensively used in organic transformations, especially those concerning the formation of nitrogen heterocycles,not many references are available for the use aza-sulfonium ylides and the Sommelet-Hauser rearrangement in the synthesis of indole derivatives. 

The synthesis starts by elaboration of a small unit that will provide the bridgehead nitrogen, the carboxyl group, and a phos-phonate unit that will close the six-membered ring by intramolecular ylide condensation. Thus, the amino group of phosphonate,... 

Several reviews on the synthesis of aziridines have been published in the previous year. These publications include a review on the silver catalyzed addition of nitrenes (among other intermediates such as carbene) across a double bond <06EJOC4313> a review on sulfur ylide addition to imines to form aziridines <06SL181> a review on nitrogen addition across double bonds <06ACR194> a general review on functionalization of a,p-unsaturated esters with some discussion of aziridination <06TA1465>... 

Carbonyl ylides derived from nitrogen-substituted carbonyl moieties provided for the synthesis of very stable push-pull dipolar intermediates. Although these compounds are quite stable, they still have sufficient reactivity to engage in cycloaddition and related processes. Carbonyl ylides derived from amides have been trapped in intermolecular cycloadditions to give aminals (Scheme 4.34) (56). 

The azomethine ylides applied in synthesis can be divided into two groups. The traditional azomethine ylide 2 is one that consists of a central nitrogen atom with three carbon substituents (Scheme 12.5). This type of azomethine ylide is most frequently formed by the condensation of an aldehyde with a secondary amine 1. The second type are the so-called stabilized azomethine ylides 4. They consist of a central nitrogen atom with two carbon substituents and the nitrogen atom also... 

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