Tandem peterson olefination and chemoselective asymmetric. Download pdf sample modern carbonyl olefination by takeshi takeda. 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. 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. Donald j peterson phd the peterson olefination reaction. Mechanism, references and reaction samples of the peterson olefination. The peterson olefination reaction provides a useful method for the preparation of alkenes from silyl carbanions and carbonyl compounds. Physical chemistry inorganic chemistry organic chemistry carbonyl compound related reaction these keywords were added by machine and not by the authors. One attractive feature of the peterson olefination is that it can be used to prepare either cis or transalkenes from the same. 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.
The peterson olefination reaction provides a useful method for the preparation of alkenes from. These keywords were added by machine and not by the authors. Mild reaction conditions thanks to high functional group tolerance of the dichromium reagent are the most beneficial aspect of this reaction. Using a peterson olefination approach, the reaction gives good to excellent yields of the alkene products and can be performed without purification of the. The wittig reaction was discovered in 1954 by georg wittig, for which he was awarded the nobel prize in chemistry in 1979. Overview of the juliakocienski olefination evans group literature seminar scott peterson sept.
Ppt the peterson olefination powerpoint presentation. The reaction of stabilized phosphonium ylides with aldehydes favors ealkene products. In contrast to the classical julia olefination, the modified julia olefination offers the possibility of saving one or two synthesis steps. The peterson olefination is the property of its rightful owner. The reaction proceeds in the absence of a transitionmetal catalyst, instead taking place by iodination of vinyl boronate complexes.
As the outcome of acid or baseinduced elimination is different, the peterson olefination offers the possibility. One of them, the wittig reaction is the representative carbonyl olefination reaction. Peterson olefination an overview sciencedirect topics. The peterson olefination reaction organic reactions. Kocienski olefination are also useful olefinating methods. Wittig reaction hornerwadsworth emmons reaction stillgennari olefination julia olefination coreywinter olefination peterson olefination bartonkellog extrusion reaction asymmetric dielsalder reaction baeyervilliger oxidation cbs reduction. Media in category peterson olefination the following 8 files are in this category, out of 8 total. 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. Methylenation of perfluoroalkyl ketones using a peterson. According to this mechanism, the first step is a carbene formation. Abstract the zweifel olefination is a powerful method for the stereoselective synthesis of alkenes. The variation in wittig reaction stereochemistry is attributed to dominant kinetic control in nearly all cases. The strong affinity of the oxygen anion for the silyl moiety is emphasised when the peterson olefination reaction takes preference. Donald john peterson was born in ladysmith, wisconsin november 19, 1935.
Wittig reaction peterson reaction julia olefination utilizing the tebbe and related reagents lowvalent chromium, zinc or titanium mediated olefination mcmurry coupling plus the. This process is experimental and the keywords may be updated as the learning algorithm improves. Concerning the mechanism of the peterson olefination reaction. Donald j peterson phd the peterson olefination reaction, buchanan, tennessee. 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. Carbenes and carbene complexes i massey university.
The peterson olefination also called the peterson reaction is the chemical reaction of. The addition of a phenylsulfonyl carbanion to an aldehyde or ketone leads to an intermediate alcohol, which is esterified in situ. 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. An interplay of 1,2 and 1,3steric interactions decides which diastereomeric oxaphosphetane will be favored. Alkenes including dienes, vinyl fluorides, vinyl chlorides, aryl bromides, and aryl iodides. This multistep synthesis enables the preparation of ealkenes. Mechanism of olefination via titaniumcarbenes the most thorough mechanistic study on tibased olefination has been done using the petasis reagent. Other similar reactions, the siliconmediated peterson olefination and two sulfurbased julia carbonyl olefinations named the julialythgoe olefination and the julia. The intermediates, both the cis and trans, can equilibrate allowing the. S1 supporting information the conjugate additionpeterson olefination reaction for the preparation of crossconjugated cyclopentenone, ppar. Kocienski explored the scope and limitation of the reaction, and today this olefination is formally known as the julialythgoe olefination. Olefination cc bond formation tokyo chemical industry.
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. Stereoselective onepot deconjugation, aldol, and stabilized peterson olefination of. The conjugate additionpeterson olefination reaction for. Carbonyl coupling reactions mcmurry reaction smith ch. Nmr spectroscopy of the crude material from the peterson reactions showed only the presence of the eisomer, demonstrating a highly selective process. Peterson in 1968, is one of the most important and widely used methods for the conversion of carbonyl compounds into alkenes 1.
Pages in category olefination reactions the following 21 pages are in this category, out of 21 total. The stereoselectivity of the julia olefination is determined by the radical intermediate. Evidence for both concerted and stepwise mechanisms for the peterson olefination reaction is presented. Disclaimer the information provided in this channel are subject to your own responsibility, this channel doesnt give any guarantee that the. This category encompasses olefination reactions, those that introduce a carboncarbon double bond into a product molecule, creating an alkene or olefin. Pdf conjugate additionpeterson olefination reactions. New developments in the peterson olefination reaction. If so, share your ppt presentation slides online with. Formation of cis or trans oxaphosphetanes is the decisive step, and this occurs by an asynchronous cycloaddition. An operationally simple, inexpensive, and rapid route for the olefination of a wide array of trifluoromethyl ketones to yield 3,3,3trifluoromethylpropenes is reported. The peterson reaction allows the preparation of alkenes from.