The wittig reaction allows the chemist to synthesize phosphoranes in the lab with relative ease. George wittig, the german chemist, has first showed the value of this procedure in the synthesis of alkenes. On the other hand, the cyclic phosphonate adduct 9a was isolated from the reaction of 1 with wittig horner reagent 6a using alcoholic sodium alkoxide. It is widely used in organic synthesis for the preparation of alkenes. Pdf wittig and wittighorner reactions under phase transfer.
Leopold horner 1911 2005 born in kehl am rhein germany. In 1958, horner disclosed a modified wittig reaction employing phosphonate stabilized. The hornerwadsworthemmons hwe reaction is a chemical reaction used in organic. A comparison of wittig and wittig horner wadsworth emmons. Background the ability to prepare alkenes is an extremely valuable reaction in organic synthesis. The wittig reaction or wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide often called a wittig reagent to give an alkene and triphenylphosphine oxide. Its time for the wittig reaction mechanism to be made easy.
Jill jaworske organic chemistry ii lab november 4th, 2019 lab. Alkenes from carbonyl compounds study questions 1 why is it important that the aldehydes added to the ylide be free of carboxylic acids. Wittighorner reaction proceeds through stepwise p p cleavage of an oxadiphosphetane intermediate, followed by a 2,3. Georg wittig was a german chemist and nobel prize winner in 1979 for the wittig reaction 1. It should not be confused with the wittig rearrangement. Industrial applications of the wittig reaction springerlink. It uses a carbonyl compound as an electrophile, which is attacked by a phosphorus ylide the wittig reagent. The purpose of this experiment was to produce 1,4diphenyl1,3butadiene from transcinnamaldehyde and transcinnamaldehyde using the wittig reaction. Phase transfer catalysis ptc is a very important method in synthetic organic chemistry having many advantages over conventional, homogenous reaction procedures. The phosphawittighorner reaction proceeds through stepwise pp cleavage of an oxadiphosphetane intermediate. Emmons reactions employs guanidine tbd and mtbd as basepromoters. Although the solubility in water appears to be an unimportant characteristic in achieving good chemical yields and ezratios, the rate of wittig reactions in water is unexpectedly accelerated.
Wittig reaction, horner wadsworthemmons reaction, water, green chemistry, onepot reaction, phase transfer. Among them, as the wittig and horner emmons reactions are the most general carbonyl olefinations, a number of improved synthetic applications have also been investigated. According to the 2010 united states census, wittig is the 12981 st most common surname in the united states, belonging to 2365 individuals. The wittig reaction or wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide often called a wittig reagent to give an alkene and triphenylphosphine oxide it is widely used in organic synthesis for the preparation of alkenes. Because the acidic proton on the carboxylic acid will protonate the negatively charged carbon, destroying the ylide. In the following article, an overview of the scope of wittig and hwe olefination reactions in water or in multiphasic media under phase transfer conditions is. Modifications of this procedure include use of a horner wadsworthemmons reagent or inclusion in a multistep synthesis ie. Organic chemistry portal, wittighornerreaction rsc ontology id, rxno.
Wittig reaction plural wittig reactions a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide to give an alkene and triphenylphosphine oxide. The reaction mechanism is similar to the mechanism of the wittig reaction. Horner wittig reaction plural horner wittig reactions. One major milestone in this regard is the horner wadsworthemmons hwe reaction, a slightly di erent approach to the wittig reaction that is based on a modi ed wittig 1. The mechanism of the homogenous reaction, discovered by georg wittig 2, involves two main steps. The wittig reaction in carbohydrate chemistry pdf free download. The alkene product 4 that you make today is the one that was used a few weeks ago as the colorizer for the chemiluminscence experiment it gave the green solution.
If a potassium base was used to generate the phosphine oxide anion, the reaction with a carbonyl compound proceeded as in. Wittig and wittighorner reactions under phase transfer. Emmons further defined the reaction in contrast to phosphonium ylides used in the wittig reaction, phosphonatestabilized carbanions are more nucleophilic but less basic. Recent applications of the hornerwadsworthemmons reaction. Abstract2phenylmethylene 1,3diphenylpropanedione 1 reacts with wittig horner reagent 6a in the presence of sodium hydride as a base to give the novel phosphonate product 8a. Eselective phosphonate esters are easily deprotonated and are more basicnucleophilic than stabilized ylides. Synthesis of stilbene by the wittig and horner wadsworthemmons reactions. The wittig reaction is an important method for the formation of alkenes.
A new mannichtype reaction of aryl propiolaldehydes with benzofuran32hone and cyclic secondary amines was established, enabling a completely stereoselective protocol to access a series of unreported. Methylenation with phosphorus ylids wittig reaction. For the wittig reaction follow the procedure in the book. Despite of the synthetic versatility of the pwh reaction, it has been a greatly underexplored method for the preparation of phosphaalkenes. These reactions differ from each other depending on the. Wittig reaction is an organic chemical reaction wherein an aldehyde or a ketone is reacted with a wittig reagent a triphenyl phosphonium ylide to yield an alkene along with triphenylphosphine oxide.
They are even now widely used for this transformation. The wittighorner reaction for the synthesis of neratinib. Wittig reactions are more general in that the product carbonyl does not need to have an attached carbonyl. Novel basefree catalytic wittig reaction for the synthesis of highly functionalized alkenes. A comparison of wittig and wittig horner wadsworth emmons reagents in reactions with some. Horner emmonswitting reaction in this experiment, a modified wittig reaction will be carried out to synthesize an alkene product. Aza wittig reactions are similar to wittig reactions in that they also involve the reaction of a phosphonium ylide, in this case an iminophosphorane or phosphinimide such as 39, with a carbonyl group containing compound to form the carbonnitrogen double bond of an imine along with a byproduct phosphine oxide such as 2. Jan 24, 2012 phosphawittighorner reagents with unsaturated substituents at iiip 10d,e can be prepared in analogous procedures. Carolyn jackson, talesha watson, claud bugheni date submitted. There are a number of reactions that can be used to prepare alkenes, but one of the most important is the wittig reaction. Pdf recent applications of the hornerwadsworthemmons. Water is an efficient medium for wittig reactions employing. In the horner wadsworthemmons modification, formation of the ylide from a phosphonate ester allows much easier isolation of the product alkene, since the sodium phosphate salt byproduct is watersoluble.
Wittig reaction scope and limitations scope limitations. Wittig and hornerwadsworthemmons olefination in aqueous. Solventfree method for making olefinic amino esters 205 from an aldehyde compound and a phosphonate derivative of glycine. Mechanism the general mechanism of the wittig reaction is shown above. The reaction of stabilized phosphonium ylides with aldehydes favors ealkene products. The double bond forms specifically at the location of the original aldehyde or ketone. Scalable preparation of methylated andotype horner. Permission is granted to copy, distribute andor modify this document under the terms of the gnu free documentation license, version 1. Synthesis of stilbene by the wittig and hornerwadsworth.
Likewise, phosphonatestabilized carbanions can be alkylated. Mechanism of the phosphawittighorner reaction arkhypchuk. Lab report 7wittig and hornerwadsworthemmons reactions. Stereochemistry, mechanism, and selected synthetic aspects. In 1958, leopold horner published a modified wittig reaction using phosphonatestabilized carbanions. The first step involves nucleophilic attack by the phosphorus on the alkyl halide, followed by the halide ion dealkylation of the resulting trialkoxyphosphonium salt. Unlike elimination reactions such as dehydrohalogenation of alkyl halides, which produce mixtures of alkene regioisomers determined by saytzeffs rule, the wittig reaction forms the double bond in one position with no ambiguity. This is followed by a presentation of the current state of the art regarding phosphinecatalyzed wittig reactions. The wittig olefination reaction and modifications involving phosphorylstabilized carbanions. Wittig and wittig horner reactions are favorite tools in preparative organic chemistry.
The purpose of this experiment is to synthesize trans92phenylethenyl anthracene from benzyltriphenylphosphonium chloride and 9anthraldehyde through the reaction mechanism recognized as the wittig reaction. Students are reintroduced to dry glassware techniques, recrystallization, and stereochemical determination by nmr. Follow me in my walkthrough video and we can do the mechanism together. View lab report lab report 7 wittig and horner wadsworthemmons reactions. This approach could tolerate various cyclic secondary amines including four, five, sixmembered and bicyclic rings with. Olefination cc bond formation tokyo chemical industry. Wittig reaction mechanism with reagent preparation. The wittig reaction has become a popular method for alkene synthesis precisely because of its wide applicability. Horner published a novel wittig reaction between phosphineoxide stabilized carbanions and carbonyl compounds 1, which was further modified by w. The reactions of wittighorner reagents and dialkyl. The phospha wittig horner reaction top, for which the mechanism is unknown, and the carbonanalogue horner wadsworthemmons reaction bottom. It should not be confused with the wittig rearrangement wittig reactions are most commonly used to couple aldehydes.
Difference between wittig and wittig horner reaction. Preparation and wittig reactions of organotrifluoroborato. The first section summarizes how arsenic and telluriumbased catalytic wittig type reaction systems were developed first due to the relatively easy reduction of the oxides involved. In the present article, the authors summarize first the advances in the application of the wittig reaction in the carbohydrate field through the end of. These reactions proceed overnight at room temperature, under weakly basic conditions, and as such extend the applicability of the wittig reaction. The wittig reaction in industrial practice pommer 1977. A more recent and inexpensive version of the reaction is the wittig horner reaction 1. The wittig reaction was discovered in 1954 by georg wittig.
Phosphorus, sulfur, and silicon and the related elements. The reaction is easy to carry out and proceeds under mild conditions. Synthesis of alkenes intro the wittig reaction is one of the premier methods for the synthesis of alkenes. The mechanism beings with attack of the pph 3 on the alkyl halide which releases the halide anion and forms a phosphonium ion. Some of them allow providing easer workup procedures and increasing the stereoselectivity of the double bond of olefins. Jun 17, 20 the phosphawittighorner reaction top, for which the mechanism is unknown, and the carbonanalogue hornerwadsworthemmons reaction bottom. Wittig and horner wadsworthemmons hwe olefination remains a series of powerful reactions in the tool kit of organic synthesis. The horner wadsworthemmons hwe reactions are vital to the chemical synthesis of complex molecules, forging a carboncarbon double bond in the generation of. Mechanism of the phosphawittighorner reaction ncbi.
Wittig reaction the wittig reaction is the reaction of an aldehyde or ketone with a triphenyl phosphonium ylide to give an alkene and triphenylphosphine oxide. The wittig reaction is an organic reaction used to convert a primary or secondary alkyl halide and an aldehyde or ketone to an olefin using triphenylphosphine and base. The wittig reaction was discovered in 1954 by georg wittig, for which he was awarded the nobel prize in chemistry in 1979. In the following article, an overview of the scope of wittig and hwe olefination. Further development of the wittig reaction in carbohydrate chemistry is demonstrated by the many publications each year on this topic. The reaction has become a widespread standard tool in natural products total syntheses, providing access to relatively simple as well as highly complex synthetic targets. Unlimited viewing of the articlechapter pdf and any associated supplements and figures. The horner wadsworthemmons hwe version of the wittig reaction focuses on the use of more stabilized phosphonate ylides 203. He was born in berlin, on june 16, 1897, and died august. The key difference between wittig and wittig horner reaction is that wittig reaction uses phosphonium ylides, whereas wittig horner reaction uses phosphonatestabilized carbanions wittig reaction and wittig horner reactions are important synthesis reactions in organic chemistry, which produce alkenes from aldehydes or ketones. Revisiting the phosphawittighorner reaction organometallics. In 1958, horner disclosed a modified wittig reaction employing phosphonatestabilized. In this study, it was used for the synthesis of the anticancer drug neratinib.
This reaction is named after its discoverer, the german chemist georg wittig. The tebbe olefination reaction follows a mechanism similar to the wittig. In fact, the discoverer of this reaction, george wittig, was awarded the 1979. The reaction of nonstabilized phosphonium ylides with aldehydes favors. The horner wadsworthemmons reaction has evolved in the last years as one of the most powerful and reliable method for stereocontrolled olefin synthesis. The suggested mechanism for the formation of these two products involves initial nucleophilic displacement of the bromine, followed by addition of a second. The wittig reaction chem 115 fan liu stabilized ylides are proposed to have a later and more productlike transition state with 1e thermodynamically favored over 1z. The reaction between a phosphorane and an aldehyde or a ketone to form a phosphine oxide and an alkene is known as the wittig reaction fig. The wittig reaction was discovered in 1954 by georg wittig and desc ribed in his pioneering publication titled uber triphenylphosphinmethylene als ole.
The effects of a scientific discovery on industrial practice are illustrated with reference to the wittig reaction. A copy of the license is included in the section entitled gnu free documentation license. Angewandte chemie international edition 20, 52 25, 64846487. Mar 01, 2007 when the reaction was performed with nbuli or nah in thf, the wittig reactions did not completely generate 7 due to the poor solubility of 4 in thf table 1, entries 1 and 2. The reaction of aldehydes or ketones with stabilized phosphorus ylides phosphonate carbanions leads to olefins with excellent eselectivity. Sep 28, 2012 the wittighorner reaction is a classic method to get alkenes by reaction phosphonates with carbonyl compounds. Wittig and wittighorner reactions under phase transfer catalysis conditions article pdf available in central european journal of chemistry 14. The hornerwadsworthemmons modification of the wittig. If a potassium base was used to generate the phosphine oxide anion, the reaction with a carbonyl compound proceeded as in the wittig. Wittig olefination of aromatic, heteroaromatic, and aliphatic aldehydes yields 63% and a ketone yield 42% are demonstrated. Schlosser 12 proposed betaines as wittig reaction intermediates. Retinoic acid phosphonium salt carotenoid synthesis wittig reaction triphenylphosphine oxide these keywords were added by machine and not by the authors. Novel basefree catalytic wittig reaction for the synthesis. The stereochemistry is set by steric approach control, where the antiperiplanar approach of the carbanion to the carbon of the carbonyl group is favored when the smaller aldehydic hydrogen eclipses the bulky phosphoranyl moiety.
Despite their frequent use, the zstereoselective formation of. Wittig and wittig horner reactions under phase transfer catalysis conditions article pdf available in central european journal of chemistry 14. Water is demonstrated to be an excellent medium for the wittig reaction employing stabilized ylides and aldehydes. While many other routes to alkenes can proceed via elimination reactions e1 or e2.
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