The nucleophilic carbon atom of the ylide reacts with the Michael group first and in the second step the electrophilic part is displaced as the leaving group with ring closure. A chiral moiety can then interact or is part of either with the carbonyl group (amine organocatalysis) or with the leaving group. Pioneering work originates from Johnson & Schroeck using a oxosulfonium methylide (1968 DOI) and from Trost & Hammen (sulfonium ylide, 1973 DOI). Phosphonium ylide MIRC reactions exist since 1988 (Krief et al. DOI)
First of is Aggarwal whose group in 2001 building on asymmetric epoxidations and aziridations ( DOI) invented an complex indirect sulfonium ylide method (DOI).
The first report clocks around 50 citations to date but is applied only once in a total synthesis of eicosanoids(DOI) and not very successfully as enantioselectivity for the particular step is poor.
A third method (Kunz/MacMillan, 2005) is a direct sulfonium ylide method DOI. An improved catalyst exists (DOI).
Other ylide reactions are reported: those base on arsenic (Zhao et al. 2007 DOI), those based on tellurium (Liao 2003 DOI) and those with azetidinium ylides (Couty 2007 DOI)
Dehydro Diels-Alder reaction
18 July 2008 - Synth. methods
Reaction name - Dehydro Diels-Alder reaction (DDA) Extension of - Diels-Alder reaction Most recent review - Chem. Rev. 2008, 108, 20512063 DOI
Main characteristics - in a DDA reaction one or more double bonds in a regular Diels-Alder are replaced by an alkyne. The primary cyclic reaction product contains an allene group. To reduce steric strain the cyclic allene will engage in secondary reactions, for instance secondary DA reactions or retro-DA reactions or those forming an arene compound. Depending on the nature of the reactants (alkene, alkyne, enynediyne) 4 reaction types are identified. Reaction is thermal or photochemical and can be catalyzed by zerovalent palladium.
H/D exchange in organic chemistry is a simple tool in structure elucidation unmasking any proton (for example that of a alcohol or an amine) as an acidic proton simply by exposing it to heavy water (D2O). Extending this scope to simple alkanes is not exactly obvious but can be done with a little bit of help of organometallic chemistry.
Deuterated alkanes can be used as molecular markers in a whole range of applications. Shilov (see Shilov system) in 1969 using platinum observed deuteration in methane (no need bothering with DOI's for Soviet-Union era chemistry) opening up a new research field
A base is required and the reaction product is a beta-alkoxy carbonyl. Note that the same carbon framework can also be obtained in an Aldol addition between two carbonyl units.
This reaction type was first reported in 1878 by Loydl (converting fumaric acid to malic acid) (DOI) actually preceding the Michael reaction. Disadvantages are availability of the Aldol reaction, low reactivity, lack of stereoselectivity and reversibility.