Benzophenones Wittig reaction

In 1953 Wittig and Geissler (100) reported that methylene triphenyl-phosphorane reacted with benzophenone to form 1,1-diphenylethene and triphenylphosphine oxide. This experiment marked the birth of the Wittig reaction, a novel method for the conversion of carbonyl groups to olefins, and the entry of ylides into the arsenal of important synthetic tools. Since... 

C KIE in the Wittig reaction of benzophenone(carbonyl- 4C) with iso-propy/idenetriphenylphosphorane... 

Carbonyl-uCKIE in the Wittig reaction of non-stabilizedylides with benzaldehyde and benzophenone... 

The nucleophilic character of triphenylphosphine and the electrophilic character of carbenes suggested to two groups of investigators that the two reagents should combine to form ylides of a new type to use in expansion of the Wittig reaction. Speziale et ai. found that triphenylphosphine on treatment in pentane with chloroform and potassium t-butoxide at 0° gives yellow triphenylphosphine dichloromethylene, which reacts with benzophenone to yield I,l-diphenyl-2,2-dichloroethylene (1). 

A further mechanistic study of the Wittig reaction between lithium-free isopropylidenetriphenylphosphorane (58) and benzophenone (59) in THF was shown by 51p n.m.r. to proceed via the oxaphosphetan intermediate (60) with ki= 1.3 x 10"3 lmol l s l, k2 = 4.0 x lO" s l and k3 = 7.0 x 10"4 s l. In addition carbonyl kinetic isotope effects and a value of p = +1.4 based on variations of substituents in the aryl group of the ketone, were consistent with rate-determining formation of the oxaphosphetan (60).23... 

Ketones.- A 3 Ip n.m.r.-based kinetic investigation of the Wittig reaction of isopropylidenetriphenylphosphorane with benzophenone provides the first example where both formation and decomposition of the oxaphosphetane intermediate can be monitored in the same reaction.3 2... 

The Wittig reaction is a very elegant method of converting a carbonyl group into a C=C bond. It was first used by Wittig and Geissler999 who treated methylenetriphenylphosphorane (triphenylphosphine methylene) with benzophenone and obtained 1,1-diphenylethylene in 84% yield ... 

In 1953, Wittig and Geissler discovered that the reaction of benzophenone (1) with methylenetriphenylphosphorane (2) gave 1,1-diphenylethene (3) and triphenylphosphine oxide (4) in virtually quantitative yield (Scheme 1) [1]. This observation triggered the rapid development of the synthesis method termed Wittig-carbonylolefination or, in brief, the Wittig reaction or Wittig condensation . 

NaH stirred ca. 45 min. at 65-70° under Ng in excess dimethyl sulfoxide until Hg-evolution is complete, allowed to react with 1 equivalent of ethyl triphenyl-phosphonium bromide, then with 0.85 equivalent of benzophenone 1,1-di-phenyl-l-propene. Y 97.5%.—The reactivity of the methylsulfinyl carbanion (formed by reaction of NaH with dimethyl sulfoxide), which is even more basic than the trityl anion, is sufficient to convert phosphonium salts into ylides thereby permitting a simple and convenient modification of the Wittig reaction. E. J. Gorey and M. Ghaykowsky, Am. Soc. 8A, 866 (1962) / -diketones from carboxylic acid esters and ketones (s. Synth. Meth. 6, 737), sym. ) -diketones, s. J. J. Bloomfield, J. Org. Chem. 27, 2742 (1962). 

Two groups have developed means of extending the condensation of sulphinyl carbanions with carbonyl compounds, such that it becomes an alternative to the Wittig reaction, through conversion of the initial carbinol adducts into olefins. Dimsyl-lithium with benzophenone gave the initial adduct as a lithium salt, which, when treated with a chlorophosphite at -80 °C, afforded a 91% yield of diphenylethylene." The isolated initial adduct (97) could be converted into undecene by reaction first with MeS—CH CH—(CH2)sCH3... 

Polymer chain 11 contains one titanacyclobutane end group. The number of end groups was determined by trapping with benzophenone in a Wittig-type reaction, Eq. (20) [37], UV- and NMR spectroscopy revealed one diphenyl-ethenyl end group, [12]. 

In a paper edited in 1953, concerned with the preparation of the stereoisomeric forms of pentaphenylphosphorus, Wittig and GeiBler described the reaction of methylene-triphenylphosphorane 1 and benzophenone 2, forming 1,1-diphenylethylene 3 and triphenylphosphine oxide 4 (Scheme 1). Soon afterwards, it could be demonstrated that alkylidenephosphoranes (phosphine alkylenes, phosphorus ylides) generally react with carbonyl compounds such as aldehydes and ketones to give alkenes with the formation of phosphine oxide 1,2). 

The dialkoxyboiyl-substituted Wittig reagent (45) also loses boron upon reaction with benzophenone to yield another l ttig reagent that has been used in the synthesis of allenes (equation 48). ... 

Corey and co-workers " found that when powdered sodium hydride is stirred into excess dimethyl sulfoxide under nitrogen at 65-70° hydrogen is evolved with formation of a solution of the highly reactive sodium methylsulfinyl methylide (1). This salt reacts with ethyltriphenylphosphonium bromide at room temperature to form the Wittig reagent (2), as shown by its rapid reaction with benzophenone to form 1,1-diphenylpropene-l (3). The strongly basic character of methylsulfinyl... 

In 1947 Wittig and Wetterling 162> examined the reaction between tetra-methylammonium bromide and phenyllithium in ether in an effort to prepare tetramethylammonium phenyl. None of the desired product was obtained, but benzene was formed along with an insoluble material which was characterized as the lithium bromide complex of the ylid on the basis of its reactions with water, iodine, methyl iodide, and benzophenone. 

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