Formaldehyde Wittig synthesis with

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 . ... 

Vinylpolystyrene, a useful intermediate for the preparation of various functionalized supports for solid-phase synthesis [7,57-59], has been prepared by the polymerization of divinylbenzene [7], by Wittig reaction of a Merrifield resin derived phosphonium salt with formaldehyde [59-62], or, most conveniently, by treatment of Merrifield resin with trimethylsulfonium iodide and a base [63] (Figure 5.7). 

Rotane was first synthesized by Rippol and Conia29. The key steps included the synthesis of dispirononanone 13 (equation 11). Condensation of 13 with formaldehyde provided the tetrahydroxymethyl derivative 32, which was converted into the tetraspiro compound 33 by tosylation-bromination followed by reductive cyclization. Subsequent Wittig methylenation and cyclopropanation of the ketone 33 completed the synthesis (equation 30). 

PhCH2NPPh3 affords the isocyanide derivative [Os3(CO)g(CNCH2Ph)(n3-ri rri iTi -Ceo)]. The Staudinger reaction in combination with an intramolecular aza-Wittig ring closure reaction has been applied in the synthesis of quinazolin-4-ones. Other examples of intramolecular aza-Wittig reactions are reported as parts in multi-step synthetic routes. A theoretical study of the aza-Wittig reaction of HN = PX3(X = H and Cl) with formaldehyde in the gas phase and in solution has been reported. ... 

Total synthesis is applied for carotenoids on a lO t scale per year. One usually starts with the cheapest carbonyl components (formaldehyde, acetone) and carbanions (acetylide, acetoacetate, cyanide, Wittig ylides) available. A typical industrial synthesis of retinol acetate (vitamin A) is outlined in Scheme 5.3,1. 

A synthesis of 2,3-diarylpyrroles was based on the use of a difunctional phosphine imine which is capable of both Wittig and aza-Wittig condensation. <94J0C4551> The reagent is prepared from benzotriazole, formaldehyde, sodium azide and triphenylphosphine which gives the precursor 13. Reaction with methylidene-triphenylphosphorane and butyllithium generated 14 which reacted with benzil derivatives to give the pyrroles. 

In the first synthetic key step, the -ketophosphonate 2 was alkylated with 1-bromo-2-methoxyprop-2-ene. Then, the product of monoalkylation was hydrolyzed under acidic conditions to the corresponding phosphorylated 1,4-diketone 4 that was cyclized to the precursor of methylenomycin B, the 5-phospho-rylcyclopentenone 5. The Horner-Wittig reaction of the latter with formaldehyde under very mild conditions completed the synthesis of 1 in 39% overall yield (Scheme 2). 

The synthesis of a gas-generating composition starts with the synthesis of a poly(vinyltriazole). A substituted triazole salt is added to a free radical brominating reagent, such as A-bromo succinimide, and to a radical initiator to form a brominated triazole. The brominated triazole is then added to triphenylphosphine to form a Wittig salt. Formaldehyde in alkaline medium effects the formation of a vinyltriazole salt, which can be polymerized with AIBN and a catalytic amount of a cationic initiator or a Ziegler-Natta catalyst. The reaction sequence is shown in Figure 9.10. 

Another synthesis of CJH eminating from the Corey labs involved a modification of the Schlosser modification of the Wittig Reaction. Whereas Wittig reactions between non-stablilized phosphoranes and aldehydes usually provide Z-olefins, Schlosser reported a variation of this reaction that provided -olefins. His group showed that when non-stabilized phosphoranes are reacted with aldehydes in the presence of lithium halides (as opposed to the salt-free conditions that favor Z-olefins), followed by deprotonation of the intermediate adduct, and reprotonation of the resulting j3-oxido ylid, T-olefins are obtained. Corey and Yamamoto reported a variation of this reaction in which the intermediate j3-oxido ylid was treated with formaldehyde, resulting in formation of trisubstituted allylic alcohols. For example, 102 reacted sequentially with aldehyde 103 and formaldehyde to provide 105. This material was then carried on to CJH intermediate 106, and the CJH derivative where R=H. 

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