Peterson-type olefination

Addition of dimethylsulfonium methylide (122) to various Michael acceptors (121), followed by alkylation, has been reported to produce functionalized 1-substituted alkenes (124), arising via the unprecedented elimination (123), rather than the usual cyclopropanation products. In silyl substituted substrates, where a facile Peterson-type olefination is possible from the adduct, elimination took place instead. Aryl-substituted Michael acceptors (121 R1 = Ar) underwent a similar olefination to give 1-substituted styrene derivatives with moderate yields along with a side product, which arose by nucleophilic demethylation from the adduct of dimethylsulfonium methylide and arylidene malonates. Hammett studies revealed that selectivity for olefination versus demethylation increases as the aryl substituent becomes more electron deficient.164... 

Reaction of DMSB with triphenylsilyl-substituted oxiranyllithium leads to the formation of an olefinic silanol via sequential (1) coordination to the silicon, (2) Si-C bond migration, and (3) Peterson-type Si-O elimination to furnish the alkene. A pentacoordinate siliconate intermediate is presumably involved in this transformation. Therefore, it was reasonable to expect that addition of a nucleophile (methyllithium or lithium t>-propoxide) to an oxiranyl-substi-tuted SCB, which could generate a similar intermediate, would induce the C-Si bond migration to form the same silacyclopentane. Indeed, this alternative order of addition sequence provides the corresponding silanol with better efficiency (84% yield vs. 44%, Scheme 36). 

Anionic pentacoordinated 1,2-oxagermetanide was synthesized quantitatively by deprotonation of the corresponding -hydroxygermane (Scheme 10)63. Upon heating at 150 °C for 30 days, this compound equilibrated with another diastereoisomer and underwent a Peterson-type reaction with elimination of olefins (Scheme 10). 

A method that makes available aromatic and aliphatic aldehyde derived sulfin-imines 47, for the first time, was recently introduced by Davis and co-workers.23,36 This one-pot procedure entails treatment of the Andersen reagent 40 with LiHMDS to generate 44 which subsequently reacts with the lithium methoxide by-product to produce silyl sulfinamide anion 46. Reaction of 46 with the aldehyde in a Peterson-type olefination reaction affords the sulfinimine 47 in >96% ee. This method was highly effective for the preparation of arylidene sulfmamides 47 (R = aryl) which were usually obtained in 60-76% yield although the alkyl counterparts... 

Keeney, A, Nieschalk, J., and O Hagan, D., The synthesis of a-monofluorovinylphosphonates by a Peterson type olefination reaction, J. Fluorine Chem., 80, 59, 1996,... 

Four-membered heterocyclic systems have been postulated to be involved as intermediates along the reaction pathway in a number of systems allowing olefin synthesis. This is the case of the Wittig reaction (phosphorus) and a family of related reactions the boron-Wittig (boron), the Peterson (silicon) 44 and the Peterson-type reactions (germanium, tin, lead). 5,l46 11 these systems,... 

Due to their synthetic utility and pharmaceutical applications, a number of synthetic routes to a,P-unsatuiated nitriles have been developed. Classical methods include dehydration of amides [15] or aldoximes [16], Wittig- [17] and Peterson-type [18, 19] olefination processes, ammoxidation of alkenes [20], and carbocyanation of alkynes [21], These approaches suffer variously from high waste generation, low yields and poor stereoselectivity. As such the transition metal-catalysed cyanation of vinyl halides is an attractive route for the synthesis of alkaiyl nitriles. Whilst several instances of such transformations have been reported in the literature, the area remains underdeveloped, particularly in comparison to analagous cyanations of aryl halides. 

Introduction. The Peterson-type olefination reaction has emerged as an extremely useful method for the preparation of alkenes from carbonyl compounds. Synthetically useful vinylsilanes can be prepared by using the Peterson-type olefination reaction of bis(silyl)methylmetal with carbonyl compounds. Among the various reported bis(silyl)methyhnetals, [bis(2-pyri-dyldimethylsilyl)methyl]lithium is an extremely efficient reagent for the stereoselective preparation of vinylsilane. ... 

Recently, (phenylthiomethyl)trimethylsilane (1), or the anion (2) thereof, has been used to synthesize vinylsilanes from a-trimethylsUyloxiranes, in Peterson-type olefination reactions to generate vinyl sulfides, and also as a radical precursor under electrochemical conditions. Addition reactions of (phenylth-iomethyl)trimethylsilyl carbene (10), prepared via two independent methods, to olefins have also heen disclosed. ... 

Metalation of tris(TMS)phosphine with butyllithium, followed by treatment with 2,3-di-f-butylcyclopropenone, and finally addition of excess TMSCl can provide the phosphatria-fulvene 5 in high yield, via a one-pot Peterson-type olefination... 

Synthesis of Keto-acids.—a-Keto-acids are obtained in moderate to good yields by the reaction of carboxylic acid dianions with conjugated nitro-olefins at — 100°C, followed by acidic work-up. Another route to these compounds involves the C-silylation of butyrolactone enolate, followed by a Peterson-type olefination to give the vinylic ether (20), which is then oxidized to the y-keto-acid (Scheme 12). Eight examples, with yields of between 50 and 83%, along with one failure are reported. 

Other variants of olefination have also been applied to dendralene synthesis [186-188]. In 2004, Dixon and Halton [189] prepared a variety of cyclic [3]dendralenes using Peterson-type olefination reactions (Scheme 1.39). These... 

Scheme 1.39 Peterson-type olefination approach to [3]dendralenes by Dixon and Halton...

Recently, a Peterson-type olefination variant of this strategy was explored by Parrain and coworkers [203]. By incorporating a trimethylsUyl group in the pentadienyl anion equivalent 246, alcohols 248 that readily undergo Lewis-acid-catalyzed y-elimination were formed as addition products of aldehydes 247 (Scheme 1.42). The one-step, facile elimination is an improvement on the mesylation/elimination approach of Fallis. Interestingly, while alcohols of the type 248 and 251 bearing different, substituted alkenyl substituents have been... 

Scheme 1.42 Syntheses of dendralenes via Peterson-type olefination by Parrain and coworkers [203].

Alai/r[(Z)-CF=C]-Pro containing N, 0-diacylhydroxamic acid type protease inhibitors have been prepared as shown in Scheme 18 [63,64], The synthesis is based upon the use of fert-butyl-a-fluoro-trimethylsilylacetate in a variation of the Peterson olefination procedure to construct the necessary functionalized fluoroolefin. Treatment of 51 with 4 equiv. of lithium diisopropylamide (LDA) and 6equiv. of chlorotri-methylsilane at 78°C formed 52 in 71% yield. The key step is the Peterson olefination reaction of the TBDMS-protected 2-(hydroxymethyl)cyclopentanone (53) with tert-butyl-a-fluoro-a-trimethylsilylacetate (52). The fluoroolefin product was obtained as a mixture of (Z) (E) isomers (54). Separation of the double-bond isomers by column chromatography provided (Z) isomer (54) in 43% yield. Further... 

The Peterson olefination has been also investigated for the introduction of a two-carbon chain as in 132 [39,175,176]. This alternative procedure compares well with the reaction of stabilized Wittig-type reagents [compare both procedures in Ref. 175]. 

P-Elimination of a hetero-substituted C-C single bond. The best-known reactions of this type are the heteroatom -heteroatom (Het -Het ) elimination (Het = O, Hal, S,...), heteroatom -hydrogen (Het -H ) elimination, Peterson olefination, Tschugajew reaction and Corey-Winter olefination. 

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