Aldehydes phosphonate reaction

Phosphonate Aldehyde/ketone Reaction conditions % yield of alkene... 

Oxirane rings also suffer rupture when acted upon by phosphorylcarbanions. The products are then dialkyl (3-hydroxyalkyl)phosphonates Reactions between dialkyl (lithiomethyl)phosphonate and a, -unsaturated aldehydes yields dialkyl (2-hydroxyalk-3-en-1 -yl)phosphonates. ... 

Yet another synthesis which employs phosphorus(III)triesters is the reaction which occurs between diethyl trimethylsilyl phosphite and bis(alkylthio)ketals more specifically, such acetals of aromatic aldehydes react in the presence of a Lewis acid (SnCl4 was actually employed) to give diethyl (a-alkylthiobenzyl)phosphonates (reaction 17) ... 

The stability of the phosphonlum-stabiUzed enolates also means that, although they react well with aldehydes, their reactions with ketones are often poor, and it is better in these cases to use phosphonate-stabilized enolates. Being anionic, rather than neutral, these enolates are more nucleophilic. If an ester enolate equivalent is being used, the best base is the alkoxide ion belonging to the ester with a ketone enolate equivalent, use sodium hydride or an alkoxide. 

Scheme 1.42 DKR of aldehydes by reaction with chiral phosphonates. Table 1.1 DKR of aldehydes by reaction with chiral phosphonates.

Stereoselective construction of functionalized spirolactams from arene ruthe-nium(ii) complexes possessing p-amino phosphonate side chains involves their treatment with excess NaH and then addition of aldehydes. This reaction provides Z-conligurated lactams stereoselectively which constitute a pharmacologically intriguing heterocychc ring system e.g. Scheme 91). ... 

When we used a,P-unsaturated sulphones and phosphonates as well as aldehydes (acyloin reaction) as electrophiles to trap the metalated aminonitriles, moderate to good ee-values were obtained and we are still engaged to optimize these variants [58]. 

Phosphonate carbanions, formed by percolation of a dilute ether solution of the diethyl phos-phonate through a macroporous AER in HO" form, react with carbonyl compounds in Horner-Wittig syntheses of alkenes (Scheme 20). " a,j -Unsaturated nitriles are formed from both aldehydes and ketones, but a,) -unsaturated esters are formed only from aldehydes. The reactions... 

Adducts from various quaternary salts have been isolated, in reactions with aldehydes, a-ketoaldehydes, dialkylacylphosphonates and dialkyl-phosphonates, isocyanates, isothiocyanates, and so forth (Scheme 15) (36). The ylid (11) resulting from removal of a Cj proton from 3.4-dimethyl-S-p-hydroxyethylthiazolium iodide by NEtj in DMF gives with phenylisothiocyanate the stable dipolar adduct (12) that has been identified by its NMR spectrum and reactional product, such as acid addition and thiazolidine obtention via NaBH4 reduction (Scheme 16) (35). It must be mentioned that the adduct issued from di-p-tolylcarbodiimide is separated in its halohydrogenated form. An alkaline treatment occasions an easy ring expansion into a 1,4-thiazine derivative (Scheme 17) (35). 

The reaction has been extended to include carbanions generated from phosphonates. This is often referred to as the Horner-Wittig or Homer-Emmons reaction. The Horner-Emmons reaction has a number of advantages over the conventional Wittig reaction. It occurs with a wider variety of aldehydes and ketones under relatively mild conditions as a result of the higher nucleophilicity of the phosphonate carbanions. The separation of the olefinic product is easier due to the aqueous solubility of the phosphate by-product, and the phosphonates are readily available from the Arbusov reaction. Furthermore, although the reaction itself is not stereospecific, the majority favor the formation of the trans olefin and many produce the trans isomer as the sole product. 

Aldehyde 170 is to serve as the electrophile in an intermolecular Homer-Wadsworth-Emmons (HWE) reaction70 with enantiomeri-cally pure phosphonate 169. Compounds 169 and 170 can in fact be joined efficiently under the mild reaction conditions shown in Scheme 50 to give a,/ -unsaturated imide 206 (96 % yield). The use... 

Another method for the preparation of hydroxyalkanephosphonic acids is the conversion of aldehydes with dialkyl phosphites in the presence of triethylamine or sodium methylate leading directly to the corresponding a-hydroxyalkane-phosphonates. This reaction is reversible, leading to the starting materials aldehyde and diethyl phosphite again [143,146]. 

Alkylation of enamines Addition of amines to triple-bond compounds Addition of amines to aldehydes or ketones Reaction between Grignard reagents and formamides Reaction of phosphonates with aldehydes or ketones... 

The reaction of the aldehyde 174, prepared from D-glucose diethyl dithio-acetal by way of compounds 172 and 173, with lithium dimethyl methyl-phosphonate gave the adduct 175. Conversion of 175 into compound 176, followed by oxidation with dimethyl sulfoxide-oxalyl chloride, provided diketone 177. Cyclization of 177 with ethyldiisopropylamine gave the enone 178, which furnished compounds 179 and 180 on sodium borohydride reduction. 0-Desilylation, catalytic hydrogenation, 0-debenzyIation, and acetylation converted 179 into the pentaacetate 93 and 5a-carba-a-L-ido-pyranose pentaacetate (181). 

The synthetic P-o-glucopyranoside 30 was converted to the cyanoglucoside rho-diocyanoside A (38a), which was isolated from the underground part of Rhodiola quadrifida (Pall.) Fisch. et Mey. (Crassulaceae) and found to show antiallergic activity in a passive cutaneous anaphylaxis test in rat. Acetylation of 30 gave an acetate (98% yield) which was subjected to ozonolysis to afford the aldehyde 39. The Horner-Emmons reaction of 39 using diethyl (l-cyanoethyl)phosphonate furnished (Z)-40a (32% yield from 30) and ( )-40b (10% yield from 30). The physical... 

OS 79] ]R 17] ]no protocol] 4-Methoxybenzaldehyde and methyl diethoxyphos-phonoacetate were reacted by means of the Wittig-Horner-Emmons reaction [85] (see a more detailed description in [42]). A modified micro reaction system consisting of two mixers, for deprotonation of the phosphonates and introduction of the aldehyde, connected to an HPLC capillary of 0.8 m length and 0.25 mm diameter was employed. The micro reactor showed higher yields than laboratory batch synthesis. 

The discussion of the activation of bonds containing a group 15 element is continued in chapter five. D.K. Wicht and D.S. Glueck discuss the addition of phosphines, R2P-H, phosphites, (R0)2P(=0)H, and phosphine oxides R2P(=0)H to unsaturated substrates. Although the addition of P-H bonds can be sometimes achieved directly, the transition metal-catalyzed reaction is usually faster and may proceed with a different stereochemistry. As in hydrosilylations, palladium and platinum complexes are frequently employed as catalyst precursors for P-H additions to unsaturated hydrocarbons, but (chiral) lanthanide complexes were used with great success for the (enantioselective) addition to heteropolar double bond systems, such as aldehydes and imines whereby pharmaceutically valuable a-hydroxy or a-amino phosphonates were obtained efficiently. 

Scheme 2.18 gives some representative olefination reactions of phosphonate anions. Entry 1 represents a typical preparative procedure. Entry 2 involves formation of a 2,4-dienoate ester using an a, 3-unsaturated aldehyde. Diethyl benzylphosphonate can be used in the Wadsworth-Emmons reaction, as illustrated by Entry 3. Entries 4 to 6 show other anion-stabilizing groups. Intramolecular reactions can be used to prepare cycloalkenes.264... 

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