Editing Ylide (section)

==Other types==

===Based on sulfur===
Other common ylides include '''sulfonium ylides''' and '''sulfoxonium ylides'''; for instance, the [[Corey-Chaykovsky reagent]] used in the preparation of [[epoxide]]s or in the [[Stevens rearrangement]].

===Based on oxygen===
'''Carbonyl ylides''' (RR'C=O<sup>+</sup>C<sup>−</sup>RR') can form by ring-opening of [[epoxide]]s or by reaction of [[carbonyls]] with electrophilic [[carbenes]],<ref>{{cite journal |first1=Albert |last1=Padwa |title=Catalytic Decomposition of Diazo Compounds as a Method for Generating Carbonyl-Ylide Dipoles |journal=[[Helvetica Chimica Acta]] |year=2005 |volume=88 |issue=6 |pages=1357–1374 |doi=10.1002/hlca.200590109}}</ref> which are usually prepared from [[diazo]] compounds. '''Oxonium ylides''' (RR'-O<sup>+</sup>-C<sup>−</sup>R'R) are formed by the reaction of [[ethers]] with electrophilic [[carbenes]].

===Based on nitrogen===
Certain [[nitrogen]]-based ylides also exist such as '''[[azomethine ylide]]s''' with the general structure:
:[[File:Azomethine ylide 2.svg|150px]]

These compounds can be envisioned as [[iminium]] cations placed next to a [[carbanion]]. The [[substituent]]s R<sub>1</sub>, R<sub>2</sub> are [[electron withdrawing group]]s. These ylides can be generated by condensation of an α-[[amino acid]] and an [[aldehyde]] or by thermal ring opening reaction of certain N-substituted [[aziridines]]. 

The further-unsaturated [[nitrile ylide]]s are known almost exclusively as unstable intermediates.  

A rather exotic family of dinitrogen-based ylides are the [[isodiazene]]s (R<sup>1</sup>R<sup>2</sup>N<sup>+</sup>=N<sup>–</sup>), which generally decompose by extrusion of dinitrogen.

[[Stable carbene]]s also have a ylidic resonance contributor, ''e.g.'':
:[[Image:Stable-carbene-resonance-2D.png|300px]]

===Other===
'''Halonium ylides''' can be prepared from allyl halides and metal [[carbenoid]]s. After a [2,3]-rearrangement, a homoallylhalide is obtained.

The active form of [[Tebbe's reagent]] is often considered a titanium ylide. Like the Wittig reagent, it is able to replace the oxygen atom on carbonyl groups with a methylene group. Compared with the Wittig reagent, it has more functional group tolerance.