Mechanism, references and reaction samples of the peterson olefination. Other similar reactions, the siliconmediated peterson olefination and two sulfurbased julia carbonyl olefinations named the julialythgoe olefination and the julia. Stereoselective onepot deconjugation, aldol, and stabilized peterson olefination of. In contrast to the classical julia olefination, the modified julia olefination offers the possibility of saving one or two synthesis steps. This multistep synthesis enables the preparation of ealkenes. As alkenes hold a pivotal role in synthetic methodology for the introduction of vicinal functionality, particularly in a stereoselective manner, the peterson reaction is increasing in importance in the reaction repertoire. The variation in wittig reaction stereochemistry is attributed to dominant kinetic control in nearly all cases. The peterson olefination is the property of its rightful owner. Mechanism of olefination via titaniumcarbenes the most thorough mechanistic study on tibased olefination has been done using the petasis reagent. Physical chemistry inorganic chemistry organic chemistry carbonyl compound related reaction these keywords were added by machine and not by the authors. The conjugate additionpeterson olefination reaction for. The peterson olefination reaction organic reactions. Concerning the mechanism of the peterson olefination reaction. Evidence for both concerted and stepwise mechanisms for the peterson olefination reaction is presented.
If so, share your ppt presentation slides online with. Carbonyl coupling reactions mcmurry reaction smith ch. This process is experimental and the keywords may be updated as the learning algorithm improves. Peterson olefination an overview sciencedirect topics. While this important reaction class is among the most important and most widely used in organic chemistry, this is the first book to summarize the many different olefination methods, including. Olefination cc bond formation tokyo chemical industry. Using a peterson olefination approach, the reaction gives good to excellent yields of the alkene products and can be performed without purification of the. Carbonyl olefination r 1 r 2 o reagent r 1 r 2 r 3 last year you met the wittig and related reactions as well as the peterson olefination some schrock carbene complexes can also achieve this transformation titanium complexes like tebbes or petasis reagent can olefinate a wider range of substrates than the wittig reaction. Nmr spectroscopy of the crude material from the peterson reactions showed only the presence of the eisomer, demonstrating a highly selective process. The strong affinity of the oxygen anion for the silyl moiety is emphasised when the peterson olefination reaction takes preference over both the julia and wittig reactions in.
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. New developments in the peterson olefination reaction. These keywords were added by machine and not by the authors. 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. Carbenes and carbene complexes i massey university. Donald john peterson was born in ladysmith, wisconsin november 19, 1935. Alkenes including dienes, vinyl fluorides, vinyl chlorides, aryl bromides, and aryl iodides. Formation of cis or trans oxaphosphetanes is the decisive step, and this occurs by an asynchronous cycloaddition. Kocienski olefination are also useful olefinating methods. The peterson olefination reaction provides a useful method for the preparation of alkenes from silyl carbanions and carbonyl compounds. In the case of trisubstituted alkenes 311 in which r 1 and r 2 are components of a ring or are identical, the reaction may prove to be the method of choice. Media in category peterson olefination the following 8 files are in this category, out of 8 total. Mild reaction conditions thanks to high functional group tolerance of the dichromium reagent are the most beneficial aspect of this reaction. S1 supporting information the conjugate additionpeterson olefination reaction for the preparation of crossconjugated cyclopentenone, ppar.
Overview of the juliakocienski olefination evans group literature seminar scott peterson sept. Disclaimer the information provided in this channel are subject to your own responsibility, this channel doesnt give any guarantee that the. Tandem peterson olefination and chemoselective asymmetric. Download pdf sample modern carbonyl olefination by takeshi takeda. Peterson in 1968, is one of the most important and widely used methods for the conversion of carbonyl compounds into alkenes 1. An interplay of 1,2 and 1,3steric interactions decides which diastereomeric oxaphosphetane will be favored. Pages in category olefination reactions the following 21 pages are in this category, out of 21 total. The reaction proceeds in the absence of a transitionmetal catalyst, instead taking place by iodination of vinyl boronate complexes. The wittig reaction was discovered in 1954 by georg wittig, for which he was awarded the nobel prize in chemistry in 1979. Hydroxy silanes can be converted to olefins either by treatment with base, through a fourmembered cyclic silaoxetane, in a strictly synelimination, or by treatment with acid, more analogous to an e 2 elimination, with strctly anti stereochemistry. An operationally simple, inexpensive, and rapid route for the olefination of a wide array of trifluoromethyl ketones to yield 3,3,3trifluoromethylpropenes is reported. Donald j peterson phd the peterson olefination reaction, buchanan, tennessee. According to this mechanism, the first step is a carbene formation.
Wittig reaction hornerwadsworth emmons reaction stillgennari olefination julia olefination coreywinter olefination peterson olefination bartonkellog extrusion reaction asymmetric dielsalder reaction baeyervilliger oxidation cbs reduction. The strong affinity of the oxygen anion for the silyl moiety is emphasised when the peterson olefination reaction takes preference. The peterson olefination reaction provides a useful method for the preparation of alkenes from. The reaction of stabilized phosphonium ylides with aldehydes favors ealkene products. Pdf conjugate additionpeterson olefination reactions.
Abstract the zweifel olefination is a powerful method for the stereoselective synthesis of alkenes. The intermediates, both the cis and trans, can equilibrate allowing the. Ppt the peterson olefination powerpoint presentation. One of them, the wittig reaction is the representative carbonyl olefination reaction. The peterson reaction allows the preparation of alkenes from. The stereoselectivity of the julia olefination is determined by the radical intermediate. Methylenation of perfluoroalkyl ketones using a peterson. The peterson reaction, as shown in equation 70, has been applied to the synthesis of alkenes that are hindered and difficult to form by the wittig reaction. The peterson olefination also called the peterson reaction is the chemical reaction of. Donald j peterson phd the peterson olefination reaction. General characteristicsthe synthesis of alkenyl halides from aldehydes using the gemdichromium reagent prepared from haloform chx 3 and crcl 2 is known as the takaiuchimoto reaction. This category encompasses olefination reactions, those that introduce a carboncarbon double bond into a product molecule, creating an alkene or olefin.
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