Olefination of aldehydes

Tertiary arsines have been widely employed as ligands in a variety of transition metal complexes (74), and they appear to be useful in synthetic organic chemistry, eg, for the olefination of aldehydes (75). They have also been used for the formation of semiconductors (qv) by vapor-phase epitaxy (76), as catalysts or cocatalysts for a number of polymeri2ation reactions (77), and for many other industrial purposes. 

In 1982, a new reaction was reported by Tamura and Ono namely, allylic nitro compounds undergo replacement of the nitro group by various nucleophiles in the presence of a palladium (0) catalyst.17a b 18a b The details of these reactions are discussed in Ref. 2b here, only some typical examples are presented. Carbon, sulfur, nitrogen, and phosphorous centered nucleophiles replace the nitro groups at the allylic positions. The reaction of allylic nitro compounds with triphenylphosphine is applied to the highly stereoselective olefination of aldehydes (Eqs. 7.15-7.18).19... 

There are several new methodologies based on the Julia olefination reaction. For example, 2-(benzo[t/Jthiazol-2-ylsulfonyl)-j -methoxy-i -methylacetamide 178, prepared in two steps from 2-chloro-iV-methoxy-jV-methylacetamide, reacts with a variety of aldehydes in the presence of sodium hydride to furnish the ajl-unsaturated Weinreb amides 179 <06EJOC2851>. An efficient synthesis of fluorinated olefins 182 features the Julia olefination of aldehydes or ketones with a-fluoro l,3-benzothiazol-2-yl sulfones 181, readily available from l,3-benzothiazol-2-yl sulfones 180 via electrophilic fluorination <06OL1553>. A similar strategy has been applied to the synthesis of a-fluoro acrylates 185 <06OL4457>. 

Olefination of aldehydes with gem-dichromium reagents.1 Reduction of 1,1-diiodoethane with CrCl2 in THF provides a 1,1-dichromioethane reagent (a) that reacts with aldehydes to furnish products of ethylidenation in 80-99% yield with high (E)-selectivity (equation I). 

The iodoetherification strategy was applied to the synthesis of the smaller fragment coupling component 109 as well (Scheme 16). Silylation of alcohol 104 [30] (76% de) allowed the separation of the pure desired diastereomer, which in turn was subjected to hydroboration/oxidation, sulfide formation with thiol 105, and oxidation to give sulfone 106. The requisite y-triethylsilyloxy alkene functionality in 107 was constructed as a diastereomeric E) Z)=l.2 l mixture by another sulfone-based olefination of aldehyde 90 with 106. Treatment of 106 with... 

Ruthenium complexes B are stable in the presence of alcohols, amines, or water, even at 60 °C. Olefin metathesis can be realized even in water as solvent, either using ruthenium carbene complexes with water-soluble phosphine ligands [815], or in emulsions. These complexes are also stable in air [584]. No olefination of aldehydes, ketones, or derivatives of carboxylic acids has been observed [582]. During catalysis of olefin metathesis replacement of one phosphine ligand by an olefin can occur [598,809]. 

Ruthenium(II)-salen complexes catalyse olefination of aldehydes by ethyl diazoacetate yields and E-selectivities are good, with electron-deficient aldehydes reacting faster.186... 

Fig. 11.7. trans-Selective Wittig olefination of aldehydes I—Preparation of a trans-configured a,j8-unsaturated ester (preparation of the starting material Figure 17.24). 

Fig. 11.8. trans-Selective Wittig olefination of aldehydes II—Synthesis of /J-carotene from a dialdehyde. The ylide used here is already known from Figure 11.2. In a way, it is "(semi)stabilized" since it is prepared in situ like a semista-bilized phosphonium ylide, but reacts as trans-selectively as a stabilized ylide. 

Fig. 11.22. Julia-Lythgoe olefination of aldehydes to form trans-alkenes in two steps (1) addition of a lithium sulfone B <-> B1 to an aldehyde in-situ acetylation (2) reduction of the syir.cmti-diastereomeric mixture of the resulting sulfonylacetates C with sodium amalgam.

For the synthesis of a heptanal derivative 30 (D in the retrosynthesis) from 19, we investigated two different approaches. The first approach relied on the Wittig olefination of aldehyde 25 (Scheme 3). The second was based on the attack of 2-lithio-2-methylpropionitrile (a-lithiated isobutyronitrile) [56-60] on the Payne rearrangement product 20 (Scheme 4). Our original attempt at the preparation of heptanal 30 from... 

This lack of generality and regioselectivity has been overcome, however, by using the 1-selenocyclopropyl aldehydes 128 a, b prepared in high yield either upon reaction of 123 with dimethylformamide or by reduction of the phenylselenocyclopropyl 129 69) with diisobutylaluminum hydride 70). Subsequent olefination of aldehydes 128 with the suitable phosphorus ylides produced the desired 1-seleno-l-vinylcyclo-propanes 130 in high yield with preferred (Z)-stereochemistry, Eq. (39) 70a). 

Fig. 9.12. tram-Selective Wittig olefination of aldehydes II—Synthesis of /3-carotene from a dialdehyde. 

A clear disadvantage is the unsatisfactory stereoselectivity observed for the olefination of aldehydes so far. However, one can easily envision that modifying the microenvironment of the reactive titanium center will bring about improvements. Better selectivities have been obtained in the olefination of carboxylic esters (Scheme 7). 

Wittig-type olefination. These complexes convert esters to vinyl ethers and ketones to olefins in 78-100% yield. They are somewhat less reactive than the corresponding Ti complexes.1 In the olefination of aldehydes, ketones, and thioketones, the (Z)-isomer is... 

The four-coordinate sqnare planar iron(n) porphyrins discussed above are not only of great valne in heme protein model chemistry, but also in chemical applications, since they undergo a wealth of ligand addition reactions. For example it has been shown that TPPFe complexes are active catalysts for important carbon transfer reactions in organic chemistry and are found to catalyze the stereoselective cyclopropanation of aUcenes, olefin formation from diazoalkanes, and the efficient and selective olefination of aldehydes and other carbonyl compounds. The active species in these carbon transfer reactions are presumably iron porphyrin carbene complexes. " It was also found that ferrous hemin anchored to Ti02 thin films reduce organic halides, which can pose serious health problems and are of considerable environmental concern because of their prevalence in groundwater. ... 

Other related reactions of these high-valent species include cyclopropanation of alkenes, oxidation of benzyltrialkylstannanes, dehydration of aldoximes, and olefination of aldehydes and ketones. Mechanisms... 

Table 20 Olefination of aldehydes with BTFP sulfones. General trends with regard to yields and stereoselectivity...

Olefination of aldehydes with a-silyl- and a-stannyl-stabilized phosphonate carbanions derived from cyclo-[L-AP4-D-Val] allow a (Z)-selective access to a,p-substituted vinyl phosphonates (343) that have been transformed into enantiomerically pure 4-alkylidene 4PA derivatives (344) (Figure 54). " Electrophilic fluorination of lithiated bis-lactim ethers derived from cyclo-[L-AP4-D Val] (345) with commercial NFSi allow direct access to a-monofluor-inated phosphonate mimetics of naturally occurring phosphoserine (346) and phosphothreonine (347), in enantiomerically pure form and suitably protected for solid-phase peptide synthesis (Figure 55). ... 

Olefination of aldehydes with the a-fluoroalkylphosphine oxide (54) provides a highly stereoselective route to the (Z)-fluoroalkenes (55) (Scheme 9).31 A similar reaction with the corresponding phosphonate gave a 1 1 mixture of ( )- and (Z)-alkenes. A new one-pot synthesis of 2-(diphenylphosphinoyl)cycloalkanes (56) by the reaction of cycloalkanone enolates with chlorodiphenylphosphine followed by oxidation has been reported (Scheme 10).32 Attempts to synthesise sarkomycin methyl ester (58) via reaction of the anion of phosphine oxide (57) with formaldehyde were unsuccessful as were similar reactions with other aldehydes, although the corresponding phosphonate anion does undergo olefination reactions. An X-ray structural analysis of (57) is reported. 

The olefination of aldehydes by diazoalkanes depends on catalysts that accept the keto oxygen from the substrate S. and transfer it to an auxiliary reagent R.. A redox process M"=0 is necessarily included in such a sequence (Scheme 3). The reduced step 0=Mo (S2C-NEt2)2 has in fact been isolated from the phosphine reduction of catalyst 4, and a carbene complex of structure 11 according to eq. (7) was suggested [8],... 

HWE olefination Stereoselective olefination of aldehydes and ketones using phosphoryl-stabilized carbanions. 212... 

Okazoe, T., Takai, K., Utimoto, K. (E)-Selective olefination of aldehydes by means of gem-dichromium reagents derived by reduction of gem-diiodoalkanes with chromium(ll) chloride. J. 7 m. Chem. Soc. 1987, 109, 951-953. 

Wittig olefination of aldehydes and ketones with triphenylcyclopropylidenephos-phorane (Route c) leads to a wide range of (organylmethylene)- or (diorganyl-methylene)-cyclopropanes in satisfactory to good yields120) (Eq. 60). 

However, biscyclopentadienyl-biscyclopropyltitanium can be used in Tebbe-type olefinations of aldehydes, ketones, and esters without ring opening. ... 

Tri-n-butylstibane (BU jSl)) mediates the olefination of aldehydes with activated... 

Derrick, A.M., and Thomson, N.M., Preparation of itaconates and succinates via olefination of aldehydes with succinate phosphonates or phosphoranes followed by optional asymmetric reduction, Pfizer, Eur. Patent Appl. EP 1199301, 2002 Chem. Abstr., 136, 325323, 2002. 

Intermediate 113 was transformed into the trimethylsilyl methyl ketone 119 in quantitative yield via the acid chloride, followed by the addition of trimethylsilylmethyl lithium (Scheme 2.13). Subsequent Peterson olefination of aldehyde 108 with 119 resulted in the required unsaturated ketone 120 in 95% yield. Subsequent desilylation and thioester hydrolysis afforded a 97% of the seco acid 121. Lactonization was achieved in 32% yield via the phosphoric acid-mixed anhydride, however this procedure also formed about 25% of the dimeric bis lactone. Following removal of the acetonide under the action of acid, a nonselective oxidation with RuCl2(Ph3P)3 produced a 1 1 mixture of the natural... 

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