Wittig reactions amino carbonyl

Among other important reactions that build up a molecule rapidly are aldol and conjugate addition. Together with Diels-Alder and Wittig reactions they are major players in organic synthesis. Another synthesis of lycoranes uses these reactions.11 Similar preliminary disconnections with the addition of a carbonyl group 89 lead to the amino acid 90. 

N-Amino groups can be alkylated and acylated by way of their anions, and they take part in the usual reactions with carbonyl compounds, with carbodiimides, and in aza-Wittig reactions. 1-Aminobenzimidazoles and their quaternary salts react similarly, and the Schiff bases formed can lead to cyclized products. 

Modifications in which the benzylic hydrogens are acidified also allow the use of mild conditions one example is the generation of a phosphonium ylide and then an intramolecular Wittig-like reaction, involving the amide carbonyl ° another variant uses a benzyl-silane. The use of an amino-silane permits reaction at both nitrogen and benzylic carbon to take place in one pot." ... 

Abstract Phosphacumulene ylides of the general formula Ph3P=C=C=X [X=0, S, NR, (0R)2] are versatile C2-building blocks. They can act either as C-nudeophiles-only in a manner typical of phosphorus ylides, or as cumulenes undergoing [2 + n -cycloadditions with other cumulenes such as CO2, COS, RNCO etc. Most prominent is their tandem addition-Wittig alkenation of hydroxy- or amino-substituted carbonyl compounds. With aptly chosen reaction partners all these pathways may lead to heterocyclic products. Some recent applications of these methods to the syntheses of azetidines, five-membered lactams, lactones, tetramates, tetronates and pyrroles as well as to six-membered quinolones and to macrolides are delineated. 

Dilithium tetrachlorocuprate is recommended as an additive for cross coupling of Grignard compounds with tosylates even allylic and benzylic acetates give good yields . a-Methylene-ketones, -carboxylic acids and -lactones have been prepared via sulfides and sulfoxides. A convenient and general synthesis of acetylene derivatives from boranes via the reaction of iodine with lithium 1-alkynyltriorganoborates has been published ar-Nitrostyrenes can be easily obtained by a Wittig synthesis with formaldehyde in an aqueous medium . A new synthesis of unsym. ketones by reaction of dialkyldiloroboranes with lithium aldimines has recently been published . Metallo aldimines have also served for the synthesis of a variety of other compound classes such as a-hydroxyketones, a-keto acids, nitriles, and for the asym. synthesis of a-amino acids . Polycondensations of malononitriles with benzylic chlorides have been carried out quantitatively under mild conditions in dimethyl sulfoxide with triethylamine as acid acceptor . Carbonyl compounds can react with dibromoacetonitrile to yield a-bromo esters with additional carbon atom . ... 

Isocyanoacrylic acid esters are useful as precursors of heterocyclic and unsaturated amino-acids. These compounds are prepared in a stereoselective manner and in good yield using the Wittig-Horner reaction of t-butyl(diphenylphosphinyl)isocyanoacetate with aldehydes. cw-Enoates have been prepared by the reaction of a-diazoesters with Rh(OAc)2. An interesting one-pot synthesis of a-fluoro-a,/3-unsaturated esters from ethyl chloromalonate and carbonyl compounds works well using spray dried potassium fluoride but not with other forms of this salt (Scheme 47) the E-ester was the major product with a stereoselectivity of 86—96%. 

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