Hetero Diels-Alder reactions of acyl phosphonates: synthesis of glycosyl type phosphonates

We have prepared glycosyl type phosphonates via hetero Diels-Alder (HDA) reactions of acyl phosphonates with electron rich dienes. HDA reactions of acyl phosphonates with Danishefsky’s diene required thermal activation to yield the desired dihydropyranones in good yield (70-91%). The reactions with Brassard’s diene involved Lewis acid promotion to yield the corresponding lactones, though in moderate yield (33-69%).     

Reactions of acyl phosphonates with organoaluminum reagents: a new method for the synthesis of secondary and tertiary α-hydroxy phosphonates

The reactions of organoaluminum reagents (trimethylaluminum, triethylaluminum, etc.) with aryl and alkyl acyl phosphonates, which lead to the formation of α-hydroxy phosphonates in moderate to good yields, are reported. This method provides easy access to secondary and tertiary α-hydroxy phosphonates depending on the reaction conditions. The reactions of triethylaluminum with a series of acyl phosphonates at 0 °C gave the secondary α-hydroxy phosphonates, while at −100 °C they afford the tertiary α-hydroxy phosphonates.     

Addition of trifluoromethyltrimethylsilane to acyl phosphonates: synthesis of TMS-protected 1-alkyl-1-trifluoromethyl-1-hydroxyphosphonates and 1-aryldifluoroethenyl phosphates

Addition reactions of nucleophilic CF3TMS to acyl phosphonates were investigated. Various acyl phosphonates reacted readily with CF3TMS in the presence of K2CO3 in DMF at rt to give 1-alkyl-2,2,2-trifluoro-1-trimethylsilyloxyethylphosphonate in 70-90% yields. When benzoyl phosphonates were used as starting material, after addition of CF3, the formed alcoholate undergoes phosphonate-phosphate rearrangement to form the acyl anion, followed by elimination of F- to give 1-aryldifluoroethenyl phosphates in 87-97% yields. As a representative example, vinylphosphate 6a was converted into 2,2-difluoro-1-phenylethanone 7 with 6 N HCl/EtOH/reflux or CAN/NaOH/MeOH/0 degrees C in 82-90% yields.     

Bifunctional Schiff base/Ti(IV) catalysts for enantioselective cyanoformylation of aldehydes with ethyl cyanoformate

A new bifunctional titanium/Schiff base catalyst was developed for the enantioselective cyanoformylation of aldehydes with ethyl cyanoformate. The reaction proceeded smoothly with a mild reaction condition to afford the cyanohydrin ethyl carbonates in high yields (up to 96%) and good enantioselectivities (up to 85% enantiomeric excess). Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of alpha-keto esters by the rhodium-catalysed reaction of cyanoformate with arylboronic acids

An arylrhodium(I) species selectively reacts with the cyano group of ethyl cyanoformate to afford the corresponding alpha-keto ester in good yield.     

A highly enantioselective catalytic Strecker reaction of cyclic (Z)-aldimines

A range of 3H-indoles and 2H-benzo[b][1,4]thiazines smoothly undergo asymmetric Strecker reaction with ethyl cyanoformate in the presence of a Cinchona alkaloid-based thiourea catalyst at 10 °C to give structurally diverse nitrogen-containing heterocycles in good to excellent yields and with excellent ee.     

Solid-phase synthesis of isoxazoles using vinyl ethers as chameleon catches

[reaction: see text] Regioselective 1,3-dipolar cycloadditions of supported vinyl ethers R(1)C(=CH(2))O-CH(2)-polymer, prepared by the Tebbe olefination of R(1)CO(2)-CH(2)-polymer, with ethyl cyanoformate N-oxide gave supported isoxazoline derivatives. Release from the support under mild acidic conditions gave the isoxazoles ethyl 5-R(1)-isoxazole-3-carboxylates. Alternatively, further on-resin functionalization of the R(1) substituent using Suzuki coupling reactions and release from the support under acidic conditions gave more structurally diverse isoxazoles.     

Highly efficient and selective olefination of acyl phosphonates with ethyl diazoacetate catalyzed by a cobalt(II) porphyrin complex

The cobalt(II) porphyrin complex (CoTPP) was found to be an efficient catalyst for the Wittig type olefination of acyl phosphonates with ethyl diazoacetate (EDA) in the presence of triphenylphosphine (Ph₃P). By using this one pot methodology under mild conditions, densely functionalized vinyl phosphonates were obtained in high yields and high E/Z selectivities in relatively short reaction times. A rather broad substrate spectrum and steric influence on the reaction rate were observed.     

Reactions of vinylphosphonates with piperazines

Russian Journal of General Chemistry - Dialkyl [2-(piperazin-1-yl)ethyl]phosphonates were obtained by the reactions of piperazine with dialkyl vinylphosphonates. The addition of...     

Synthesis of nonracemic allylic hydroxy phosphonates via alkene cross metathesis

Allylic hydroxy phosphonates and their derivatives can be interconverted by using cross metathesis with second generation Grubbs catalyst. The absolute stereochemistry of the starting phosphonate is conserved in the product. Cross metathesis reaction of the acrolein-derived phosphonate 2a yields a series of functionalized allylic hydroxy phosphonates. However, the cross metathesis reaction is often accompanied by competing dimerization and alkene migration reactions leading to a reduction in yield. The cinnamaldehyde- and crotonaldehyde-derived phosphonates 2b and 2c were also examined. In general, the metathesis reactions of phosphonates 2b and 2c are considerably slower than those for phosphonate 2a leading to mixtures. Several hydroxyl-protected derivatives of the phosphonate 2a (methyl carbonate 3a, acetate 4a, N-tosyl carbamate 5a, TBDMS 6a, and acetoacetate 7a) undergo metathesis without competing side reactions to give substituted allylic phosphonates in good to excellent yield.     

One-pot chemoenzymatic synthesis of protected cyanohydrins

In a chemoenzymatic one-pot reaction of ethyl cyanoformate with benzaldehyde catalyzed by the hydroxynitrile lyase from Prunus amygdalus ethoxycarbonylated (R)-mandelonitrile is formed in a highly enatioselective manner. The reaction was performed both in aqueous and organic media. ¹H NMR investigations revealed a two-step procedure consisting of an enzyme-catalyzed addition of HCN, generated by hydrolysis of ethyl cyanoformate, to the aldehyde followed by ethoxycarbonylation of the free cyanohydrin in a second step     

Synthesis of (3,6-dihydro-2H-pyran-2-yl)phosphonate derivatives and investigation of catalyst effect on frontier molecular orbitals using DFT method

Hetero Diels-Alder (HDA) reactions between 2,3-dimethyl-1,3-butadiene and diethyl ester of aroyl phosphonates catalyzed by AlCl₃ to afford (3,6-dihydro-2H-pyran-2-yl) phosphonate derivatives were investigated. Aroyl phosphonates with electron-withdrawing groups generally resulted in better isolated chemical yields. A stoichiometric amount of AlCl₃ rather than a catalytic amount was necessary to activate the cycloaddition reaction. The amount of AlCl₃ catalyst and its effect on LUMO of ethyl ester benzoyl phosphonate were also investigated by performing density functional theory (DFT) (B97D/6-31+G(d,p)) computations in dichloromethane. An increased loading of AlCl₃ induced a considerable decrease in the LUMO energy of ethyl ester of benzoyl phosphonate. The computed Gibbs free activation energy is 17.03 kcal/mol in DCM at 0°C using the same computational level.     

2-azabicyclo[2.2.2]octa-3,5-dione via a nitrile Diels-Alder reaction

The hetero-Diels-Alder reaction of an electron-deficient nitrile, p-toluenesulfonyl cyanide, with the silyl enol ether of cyclohexenone produced a hydrolytically sensitive [4 + 2] adduct in good yield. Use of Mander's reagent, ethyl cyanoformate, with the same diene, produced an unstable adduct. Hydrolysis of the tosyl cyanide adduct resulted in the isoquinuclidinone 2-aza[2.2.2]octa-3,5-dione as a crystalline compound in excellent yield from the nitrile.     

双功能化Salen-Ti配合物催化芳香醛的不对称氰甲酸酯化反应研究

合成了4个双功能salen-Ti配合物, 并将其应用于芳香醛的不对称氰甲酸酯化反应. 结果表明, 在优化条件下, 催化剂表现出优良的催化活性和良好的对映选择性, 化学收率为86%～95%, 产物的ee值最高可达92%.     

Cycloaddition-elimination reactions of 4-methyl-5-phenylimino-Δ2-1,2,3,4-thiatriazoline with electrophilic nitriles

4-Methyl-5-phenyliminothiatriazoline 4 undergoes two consecutive cycloaddition-elimination reactions with ethyl cyanoformate and p-toluenesulfonyl cyanide in refluxing chloroform, and yields the 1,2,4-thiadiazolines 6a,b via the isomers 5a,b . In acetone as the solvent, the reactions occur at room temperature, due to the formation of the 1,2,4-oxathiazolidine 12 as the intermediate. When trichloroacetonitrile was used, only the decomposition products of 4 , namely 7 and 8 were obtained.     

Photochemische Cycloadditionen von 3-Phenyl-2H-azirinen mit aktivierten Doppelbindungen. Vorläufige Mitteilung

Irradiation of 2-methyl- ( 1a ), 2,2-dimethyl- ( 1b ) and 2,3-diphenyl-2H-azirine ( 1c ) in the presence of diethyl mesoxalate yields the corresponding 4-phenyl-5,5-diethoxycarbonyl-3- oxazolines 3a–c . Similar cycloadducts are observed (cf. 6 ) by irradiation of 1b and 1c in the presence of trifluoroacetophenone. When ethyl cyanoformate is used as trapping agent photolysis of 1b or 1c leads to cycloadducts with the carbonyl and nitrile group, respectively which are present in the cyanoformate.     

Synthesis of Ethyl Isoxazole‐3‐Carboxylates Using an Ionic Liquid as a Soluble Support

A regioselective 1,3‐dipolar cycloadditions of ionic liquid‐supported vinyl ethers, derived from ionic liquid‐supported α‐phenylselenomethyl ether, with ethyl cyanoformate N‐oxide gave supported isoxazoline derivatives, which were then cleaved from the ionic liquid support under mild acidic conditions to afford ethyl isoxazole‐3‐carboxylates. This new synthetic method is simple and efficient and the products are obtained in good yields.     

Addition of allylindium reagents to acyl phosphonates: synthesis of tertiary α-hydroxy alkylphosphonates

Treatment of acyl phosphonates with allylindium reagents in the presence of acetic acid afforded the corresponding α-hydroxy alkylphosphonates in good yields under mild conditions.     

One‐pot solvent‐free synthesis of novel functionalized ethyl 2‐(alkylimino)‐4‐methyl‐3‐(alkanoyl)‐2,3‐dihydrothiazole‐5‐carboxylates

A green and efficient one‐pot two‐step synthesis of ethyl 2‐(alkylimino)‐4‐methyl‐3‐(alkanoyl)‐2,3‐dihydrothiazole‐5‐carboxylates from the reaction between acyl chlorides, ammonium thiocyanate, primary alkylamines, and ethyl 2‐chloroacetoacetae under mild, solvent‐ and catalyst‐free conditions at room temperature is presented. This efficient and straightforward technique gave the expected products in good to high yields in 2–4 hr without the creation of any by‐product in all reactions.     

Catalytic, asymmetric synthesis of cyanohydrin ethyl carbonates

[reaction: see text] The bimetallic titanium complex [(salen)TiO](2), where salen is the ligand derived from (R,R)-cyclohexanediamine and 3,5-di-tert-butyl-salicylaldehyde, has been shown to catalyze the asymmetric addition of ethyl cyanoformate to aldehydes leading to cyanohydrin carbonates with high enantiomeric excesses.