Ylids, nitrogen

For a review of nitrogen ylids, see Musker, W.K. Fortschr. Chem. Forsch., 1970,14, 295. For a monograph on sulfur ylids, see Trost, B.M. Melvin Jr, L.S. Sulfur Ylids Academic Press NY, 1975. For reviews, see Fava, A. in Bemardi Csizmadia Mangini Organic Sulfur Chemistry Elsevier NY, 1985, p. 299 Belkin, Yu.V. Polezhaeva, N.A. Russ. Chem. Rev., 1981, 50,481 Block, E. in Stirling The Chemistry of the Sulphonium Group,... 

A closely related reaction is formation of nitrogen ylids from quaternary ammonium salts (see 17-7) ... 

Although phosphorus ylids are most commonly used to alkenylation reactions, nitrogen ylids can occasionally be used. As an example, the reaction of A-benzyl-A-phenylpiperidinium bromide with base generated a A-ylid, which reacted with benzaldehyde to form styrene. ... 

Essentially the same mechanism is likely to be involved in an electrochemical version of the Stevens rearrangement. The mechanism of this reaction is not known with certainty however, it is known to be intramolecular and to involve deprotonation of quaternary ammonium salts to give nitrogen ylids which rapidly rearrange. The scheme set out in Scheme 9 is therefore entirety plausible. 

I. Zugravescu and M. Petrovanu, Nitrogen Ylid Chemistry, McGraw-Hill, New York, 1976. 

Although we do not know just how thiamine binds to the enzyme, the essential features of the reaction are quite well understood. Thiamine has an acidic hydrogen at the 2-position of the azathiacyclopentadiene ring, and you should recognize that the conjugate base, 10, is both a nitrogen ylid and a sulfur ylid (Section 16-4A) ... 

Addition of DMAD to the carbonyl-stabilized nitrogen ylid 329 gave the furan 330 and the isoindolenine 331. This and similar reactions201 could involve either a symmetry allowed concerted cycloaddition or a nonconcerted reaction followed by elimination of the tertiary amine. 

Dihydro-l,3,5-oxazaphospholes (1 and 2) react with alkynes at temperatures between 100° and 140°C in toluene or xylene.826 Phosphate esters are eliminated and 1 1 adducts (4) of the resulting nitrogen ylids (3) are obtained.827 Similar reactions with MP have been described and the ratio of adducts 5 and 6 studied527 with 1 the ratio was 78 22, whereas 2 gave 70 30. The photoaddition of 1 to DMAD was carried out and 4 was again obtained.628... 

To date, these three sulfur-nitrogen ylids are the only such structures to appear in the literature. It is particularly significant that 2,5-dichloro-, 2,5-dibromo-, and 2,3,4,5-tetrabromothiophenes ail fail to give ylids under similar reaction conditions. 

In this review the conditions under which a-proton abstraction occurs are examined and the properties and reactions of the resulting nitrogen ylid are described. The subject of nitrogen ylids was reviewed by Johnson 78> in 1966 in a chapter in the book entitled Ylid Chemistry . In... 

From this beginning, the chemistry of numerous nitrogen ylids has been studied, but the ylid, the simplest member of this series, has been studied most extensively and will be discussed first. 

Since the boron trifluoride adduct is the most stable adduct of the boron complexes of methylenetriphenylphosphorane 121>, it might be expected that this Lewis acid would also form a stable nitrogen ylid adduct. Treatment of the ylid with boron trifluoride gave a white crystalline solid whose properties were consistent with the proposed adduct 11 °>. The adduct decomposes to trimethylamine trifluoroborane... 

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