Alkenes Peterson olefination

The Peterson olefination can be viewed as a silicon variant of the Wittig reaction, the well-known method for the formation of carbon-carbon double bonds. A ketone or aldehyde 1 can react with an a-silyl organometallic compound 2—e.g. with M = Li or Mg—to yield an alkene 3. 

The next step of the Peterson olefination allows for the control of the E Z-ratio of the alkene to be formed by proper choice of the reaction conditions. Treatment of /3-hydroxysilanes 5 with a base such as sodium hydride or potassium hydride leads to preferential -elimination to give alkene 3a as major... 

The Peterson olefination presents a valnable alternative to the Wittig reaction. It has the advantage to allow for a simple control of the alkene geometry. Its applicability in synthesis depends on the availability of the reqnired silanes. ... 

Which of the following methods of alkene synthesis appear reasonable a) Witrig b) Homer-WtkIsworth-Emmons or c) Peterson olefination ... 

The Peterson Reaction allows the preparation of alkenes from a-silylcarbanions. The intermediate p-hydroxy silane may be isolated, and the elimination step - the Peterson Elimination - can be performed later. As the outcome of acid or base-induced elimination is different, the Peterson Olefination offers the possibility of improving the yield of the desired alkene stereoisomer by careful separation of the two diastereomeric p-hydroxy silanes and subsequently performing two different eliminations. 

The acid or base elimination of a diastereoisomerically pure p-hydroxysilane, 1, (the Peterson olefination reaction4) provides one of the very best methods for the stereoselective formation of alkenes. Either the E- or Z-isomer may be prepared with excellent geometric selectivity from a single precursor (Scheme 1). The widespread use of the Peterson olefination reaction in synthesis has been limited, however, by the fact that there are few experimentally simple methods available for the formation of diastereoisomerically pure p-hydroxysilanes.56 One reliable route is the Cram controlled addition of nucleophiles to a-silyl ketones,6 but such an approach is complicated by difficulties in the preparation of (a-silylalkyl)lithium species or the corresponding Grignard reagents. These difficulties have been resolved by the development of a simple method for the preparation and reductive acylation of (a-chloroalkyl)silanes.7... 

The Peterson olefination is a connective alkene synthesis and represents a useful alternative to the Wittig reaction. The precursors for the Peterson olefination are 3-hydroxy-alkyltrimethylsilanes which undergo P-elimination of trimethylsilanol under basic or acidic conditions to furnish stereodefined alkenes. This olefination method is especially valuable for the preparation of terminal and exo-cyc ic double bonds and for the methylenation of hindered ketones where the Wittig reaction is problematic. Also, the... 

A (Z)-selective Peterson olefination was the key step in the first enantioselective total synthesis of both enantiomers of lancifolol in the laboratory of H. Monti.This synthetic approach allowed the correlation of the relationship between absolute configuration and specific rotation. It is important to mention that no other olefination method could be applied successfully in installing this (Z)-alkene moiety. 

Peterson olefination Preparation of alkenes from a-silyl carbanions and carbonyl compounds. 344... 

The Corey-Peterson olefination is a version of the Peterson olefination that produces trisubstituted (O-rncthyl alkenes with high diastcreoselcctivity via a two-step process. 

The Peterson olefination is a two-step process for the formation of alkenes from an a-silylcarbanion and an aldehyde or ketone. The first step is an addition reaction that affords both syn and anti p-hydroxysilanes. The stereochemistry is then controlled during the elimination step by using either an acid or a base. Reviews Kano, N. Kawashima, T. In Modem Carbonyl Olefination-Methods and Applications Takeda, T. Ed. Wiley-VCH Weinheim, 2004 Chapter 2 The Peterson and Related Reactions, pp. 18-103. (b) Kelly, S. E. In Comprehensive Organic Synthesis Trost, B. M. Fleming, 1., Eds. Pergamon Oxford, 1991 Vol. 1, Chapter 3.1 Alkene Synthesis, pp. 731-737. (c) Ager, D. J. Org. React. 1990, 38, 1-223. (d) Ager, D. J. Synthesis 1984, 384-398. 

Condensation of ot-silylalkyl compounds with carbonyl compounds to form alkenes has been known as the Peterson olefination reaction. Usually an a-silanyl carbanion generated in situ... 

This reaction was first reported by Peterson in 1968. It is a two-step synthesis of olefin involving the addition of an a-silyl carbanion to a carbonyl compound to form y3-silyl alcohol (or /3-hydroxy silane) and the elimination of silol. Therefore, this reaction is generally known as the Peterson olefination. In addition, this reaction is also referred to as the Peterson reaction " and Peterson elimination. Occasionally, the Peterson olefination is also called the Peterson alkenation or Peterson alkenylation. ... 

As in much of organosilicon chemistry, the driving force in this step is provided by the formation of a highly stable Si-O bond. It s worth noting that Peterson olefination is stereoselective. For example, in the reaction below, Me3SiOH eliminates in a syn manner, that is, from a given face of the incipient alkene ... 

Similar to (chloromethyl)trimethylsilane, (chloromethyl)di-methylphenylsilane can be used to prepare alkenes via a Peterson olefination by treating C=0 compounds with Grignard 29. However, due to its propensity for rearrangements under the conditions needed for the elimination step, 1 appears less suited for this task than (chloromethyl)trimethylsilane if the silyl terminal alkenes are desired. However, in a parallel transformation, it was found that if the )3-silylalcohol 31 is treated with magnesium iodide etherate, then the Julia ring-opened homoallylation adduct 32 could be isolated (eq 15). ... 

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