Nitrogen ylides preparation

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. 

Phenyliodonium Zwitterions Preparation. Reactivity of Iodine-Carbon Ylides. Reactivity of Iodine-Nitrogen Ylides. Reactivity of 1,4-dipoles. 

Reactions which formally involve the oxidation of azides have been reviewed by Boyer. Other oxidations with useful synthetic applications include two which start from nitrogen ylides. Sulfimides (50) derived from electron-deficient aromatic and heterocyclic amines are oxidized to the corresponding nitroso compounds by MCPBA. - This is a very useful method of preparation of some otherwise inaccessible nitroso compounds such as 2-nitrosopyridine and 1-nitrosoisoquinoline. They can be further oxidized, for example by ozone, to the nitro compounds. Phosphimides (51) are oxidized directly by ozone to the nitro compounds, although the nitroso compounds are intermediates. Isocyanates can also be oxidized to the corresponding nitro compounds, by dimediyldioxiraiK (1). ... 

H-4,1,2-Benzothiadiazines 4 can be prepared by ring expansion of intermediate 3-alkyl-l, 2,3-benzothiadiazolium salts 2, possibly via nitrogen ylides 3.140 141... 

The potent cyclic AMP phosphodiesterase inhibitor (187) was cleaved to (188) and SO2 when treated with sodium methoxide in methanol. The reaction mechanism has been discussed. Irradiation of the pyridinium ylides prepared from thieno[2,3-6]- and thieno[3,2-6]-pyridine by N-amination with O-mesityl-enesulphonylhydroxylamine, followed by treatment with base, resulted in the formation of the corresponding thieno[2,3-c]- and thieno[3,2-c]-17T-l,2-diazepines. From these compounds the corresponding 3//-derivatives, such as (189), were prepared upon photolysis, these gave 3-vinyl-l//-thieno[2,3-c]-pyrazole, while thermolysis yielded 3-(3-thienyl)pyrazole. The 3-acetoxy- and 3-methoxy-derivatives of 3iT-l,2-thienodiazepines were also prepared, and their photolyses gave 3-vinylpyrazole, while thermolysis and treatment with base resulted in loss of nitrogen to give compounds such as (190). ... 

Cubane-l,4-dicarboxylic acid rearranges to cuneane-2,6-dicarboxylic acid in a water-promoted transformation via the hydrogen cubane-l,4-dicarboxylate (Scheme 215). Solutions of tetrakis(guanidino)phosphazenium salts have been prepared. Unsaturated seven-membered lactams have been converted to fused pyrrolidinolac-tones by a process that involves the formation of an ammonium salt and subsequently a nitrogen ylide which initiates the rearrangement reaction. ... 

Pyridinium ylide is considered to be the adduct car-bene to the lone pair of nitrogen in pyridine. The validity of this assumption was confirmed by Tozume et al. [12J. They obtained pyridinium bis-(methoxycarbonyl) meth-ylide by the photolysis of dimethyl diazomalonate in pyridine. Matsuyama et al. [13] reported that the pyridinium ylide was produced quantitatively by the transylidalion of sulfonium ylide with pyridine in the presence of some sulfides. However, in their method it was not easy to separate the end products. Kondo and his coworkers [14] noticed that this disadvantage was overcome by the use of carbon disulfide as a catalyst. Therefore, they used this reaction to prepare poly[4-vinylpyridinium bis-(methoxycarbonyl) methylide (Scheme 12) by stirring a solution of poly(4-vinylpyridine), methylphenylsulfo-nium bis-(methoxycarbonyl)methylide, and carbon disulfide in chloroform for 2 days at room temperature. 

Another important method for preparation for exohedrally functionalized fullerenes is the 1,3-dipolar cycloaddition of in s/Yw-generated azomethine ylides to C60 yielding fulleropyrrolidines (Maggini et al., 1993). Further functionalization is facilitated either by the use of adequate aldehydes for the azomethine ylide formation or quatemization of the pyrrolidine nitrogen atom. Both bisaddition (Kordatos et al.,... 

Diaminocarbene complexes were reported as early as 1968 [152], Preparation and applications of such complexes have been reviewed [153], Because of 7t-electron donation by both nitrogen atoms, diaminocarbenes are very weak tt-acceptors and have binding properties towards low-valent transition metals similar to those of phosphines or pyridines [18,153]. For this reason diaminocarbenes form complexes with a broad range of different metals, including those of the titanium group. Titanium does not usually form stable donor-substituted carbene complexes, but rather ylide-like, nucleophilic carbene complexes with non-heteroatom-substituted carbenes (Chapter 3). 

Table 2.21. Preparation of five-membered, nitrogen-containing heterocycles by rearrangement of chromium-carbene-derived ammonium ylides.

Photolysis or thermolysis of heteroatom-substituted chromium carbene complexes can lead to the formation of ketene-like intermediates (cf. Sections 2.2.3 and 2.2.5). The reaction of these intermediates with tertiary amines can yield ammonium ylides, which can undergo Stevens rearrangement [294,365,366] (see also Entry 6, Table 2.14 and Experimental Procedure 2.2.1). This reaction sequence has been used to prepare pyrrolidones and other nitrogen-containing heterocycles. Examples of such reactions are given in Figure 2.31 and Table 2.21. 

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