Carbonyl olefination reaction

Alcohols with organoelement groups listed in Table 13 gave with one exception only small amounts of olefine. But with hydroxyalkyl-selenides (35a, G = -SePh or -SeCHs) stereospecific frans-elimination can be achieved in acidic (for instance excess of perchloric acid ether at room temperature) or basic media to give olefines in good yield So we can state that preparatively useful carbonyl olefination reactions in which epoxides are not a by-product, are allowed not only with phosphorus and silicium containing regents but are possible in the wide area of the periodical table marked in Scheme 55c with little lines. 

The synthesis of (E)-7-methyl-4-octene-3-one (3) is a typical example of this carbonyl olefination reaction.2... 

Gilman, H., Tomasi, R. A. a-Silyl-substituted ylides. Tetraphenylallene via the Wittig reaction. J. Org. Chem. 1962, 27, 3647-3650. Peterson, D. J. Carbonyl olefination reaction using silyl-substituted organometallic compounds. J. Org. Chem. 1968, 33, 780-784. 

Bertini, F., Grasselli, P., Zubiani, G., Cainelli, G. Geminal dimetallic compounds. Reactivity of methylene magnesium halides and related compounds. General carbonyl olefination reaction. Tetrahedron 9 0, 26,1281-1290. 

Peterson, D.J., Carbonyl olefination reaction using silyl-substituted organometallic compounds, J. Org. Chem., 33, 780, 1968. 

Figure Possible energy profiles of the Wittig carbonyl olefination reaction.

The carbonyl-olefination reaction, eqn. (2), is like a Wittig reaction in which the Mt—C bond takes the place of a P=C bond, and applies to the first three entries in Table 4.1. It is important both as a means of effecting clean termination of living ROMP reactions when initiated with Ti, Mo, or W complexes, and as a convenient means of converting C=0 groups into C=CH2 or C=CHR groups in organic sjmthesis. 

The C=C bond reacts first to give [W]=CH(CH2)3C0(CH2)0(CH2)3Ph which then undergoes an internal carbonyl-olefination reaction (Fu 1993a). 

Another example of a stoichiometric carbonyl-olefination reaction facilitated by a reagent which may be assumed to generate an intermediate tungsten carbene complex is shown in eqns. (7) and (8). The ketone can be added as soon as methane evolution has subsided (Kaufftnann 1986). 

The temporary presence of a carbon-carbon double bond can be advantageous for creating branches in a molecular skeleton by bond formation. This functionality can be obtained not only by olefin metathesis, but also by any carbonyl olefination reaction (Wittig [24], Homer-Wadsworth-Emmons [25], Peterson, or Julia-Lythgoe [9]) (Scheme 3.14). 

Scheme 3.14 Approach to branches in a skeleton based on carbonyl olefination reactions...

The synthesis of F-labeled stilbenes [ F]2g, [ F]3g, and [ F]4e ( -isomers) by the FIorner-Wadsworth-Emmons reaction was accomplished [83]. This carbonyl-olefination reaction was performed via a multistep/one-pot reaction by the coupling of benzylic phosphonic acid esters (3,5-bis-methoxymethoxybenzyl)-phosphonic acid diethyl ester, (4-methoxymethoxybenzyl)phosphonic acid diethyl ester, and (4-dimethylaminobenzyl)phosphonic add diethyl ester with 4-[ F]fluor-obenzaldehyde. The radiochemical yields ranged from 9 to 22%. Three new polyfluorinated compounds ([( )-4-(4-bromostyryl)-2,3,5,6-tetrafluorobenzonitrile]x-[( )-4-(4-bromo-2,3,5,6-tetrafluorostyryl)benzonitrile]i K) were obtained by the Homer-Wadsworth-Emmons approach to study intermolecular interactions in the crystal state and the formation of cocrystals [84]. 

SECTION 2.5. THE WITTIG AND RELATED CARBONYL OLEFINATION REACTIONS... 

The synthetic utility of carbonyl olefination reactions can be expanded beyond alkene synthesis through the use of functionalized ylides and functionalized phosphonate carbanions. Thus, methoxymethylene and phenoxymethylene ylides lead to vinyl ethers which can be readily hydrolyzed to aldehydes. 

Grubbs has proposed a related mechanism for ring-opening metathesis, carbonyl-olefination reactions. 

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