Ethyl 3,4-pentadienoate

Apparatus 500-ml three-necked, round-bottomed flask with a thermometer, dipping well into the liquid, a 40-cm Widmer column and a dropping funnel the column was connected to a condenser and receiver. 

The contents of the flask were allowed to cool to 20-25°C. Very careful fractiona- 

Apparatus 500-ml round-bottomed, three-necked flask, provided with a gas inlet tube, a mechanical stirrer and a thermometer-vent combination for the preparation of the a-chloroether 500-inl round-bottomed flask, provided with a gas inlet, a reflux condenser and a thermometer, dipping in the liquid for the elimination of HCT and the 3,3-sigmatropic rearrangement. 

Starting from propionaldehyde the aldehyde H2C=CH-CH=C(CH3)CH=0 was obtained in an impure state and in moderate yield. Its precursor H2C=C=CH-CH(CH3)CH=0 was present in traces only. 

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Bohlmann and co-workers (67CB2742) have added imine I to ethyl 2,4-pentadienoate (2) to afford adduct 3 in fair yield. Adduct 3 was further transformed into the quinolizidine alkaloid lupinine (5), as shown in Scheme I. 

Oxidation of dihydrobenzenes. Ethyl 2,4-pentadienoate (2) reacts with A1-pyrrolidinocyclohexene (1) to give the 1 1 adduct of 1,4-cycloaddition (3), which undergoes reverse Michael addition and tautomerism to give (4). This is conveniently oxidized to the aromatic system (5) by Attenburrow manganese dioxide.47... 

The use of imines as dienophilic components in [4 - - 2] cycloaddition reactions is well known <79H(12)949,82T3087). For example, a Diels-Alder reaction between the tetrahydropyridine (263) and ethyl 2,4-pentadienoate was the key step in Bohlmann s synthesis of lupinine (Scheme 54) <67CB2742>. Similar methodology has been applied to the preparation of a variety of areno[a]quinolizidin-2-ones (264) <85TL1277> (Equation (29)). 

Similar carbocationic intermediates may be involved in the transformation of substituted ethyl pentadienoates under Ritter conditions in excess triflic acid (3 equiv.) to furnish the bicyclic aza compounds 163 [Eq. (5.254)].701... 

Posner and colleagues have recently made use of a [3,3]-sigmatropic rearrangement of an a,P-unsaturated sulfoxide as part of a regiospecific conversion of allylic alcohols into two-carbon-extended conjugated dienoate esters [233]. For example, reaction of allyl alcohol (291) with the sulfinyl orthoester (292) and a catalytic amount of 2,46-trimethylbenzoic acid in dichloromethane at 100°C produced ethyl pentadienoate (295) in 75% yield. The reaction is believed to... 

On 0.01-raol scale the yield of ethyl 2,3-pentadienoate is 0.79-0.93 g (64-74%). The product was purified by bulb-to-bulb distillation with a Kugelrohr apparatus at 12-14 rm with an oven temperature at 75-85 C. 

Yanovskaya and coworkers55 have reported rate constants for the alkaline hydrolysis of ethyl lruns,trans-4 -substi tuted 5-phenyl-2,4-pentadienoates in 60% aqueous dioxan giving the values X, log t, H, -2.60 Cl, -2.23 Br, -2.31 N02, -1.83 OMe, -2.61 NMe2, —3.00. Correlation with the CR equation gave as the best regression equation ... 

Ethyl (A/)-2-MethyM-phenyl-2,3-pentadienoate Typical Procedure115 ... 

At about the same time, a synthesis of leukotriene-A, also termed SRS-A ( slow reacting substance of anaphylaxis ), which made use of the Wittig olefmation was described77). The ylide of 100 is reacted with ethyl 5-formyl-2,4-pentadienoate 101 to give the ( , , Z, Z)- tetraenoic ester 102. Reduction and mesylation of 102, subsequent conversion into the sulfonium salt, and treatment of the latter with a base yields a sulfonium ylide which is reacted with methyl 4-formylbutanoate 69 to the epoxy-tetraenoic ester 103. After separation of the cis-epoxide by HPLC, 103 was treated with the S-trimethylsilyl derivative of glutathione dimethyl ester N-trifluoroacet-amide. The diastereomeric products thus obtained were separated by means of HPLC and hydrolyzed to 104 77) (Scheme 18). 

For the Isolation of relatively volatile a-allenic esters such as ethyl 2,3-pentadienoate, the submitters recommend that the rotary evaporation be carried out with cooling in an ice bath. When this precaution was taken, the submitters obtained 8.5-9.5 g (67-75%) of product after distillation. 

Cyanohydrin trimethylsilyl ethers are generally useful as precursors of carbonyl anion equivalents and as protected forms of aldehydes. Direct conversion of p-anisaldehyde into O-TRIMETHYLSILYL-4-METHOXYMANDELO-NITRILE employs a convenient in situ generation of trimethylsilyl cyanide from chlorotrimethylsilane. A general synthesis of altenic esters is a variant of the Wittig reaction. Ethyl (triphenylphosphoranylidene)acetate converts pro-pionyl chloride into ETHYL 2,3-PENTADIENOATE. 

Yanovskaya and coworkers have reported rate constants for the alkaline hydrolysis of ethyl -substituted 5-phenyl-2,4-pentadienoates in 60% aqueous dioxan... 

Early investigations of additions of soft carbon nucleophiles to simple Michael acceptors like ethyl sorbate date back to the beginning of the 20th century. Already in 1906. Vorlauder and coworkers described additions of malonate anion whereas ethyl sorbate provided the 1,6-addition product (equation 2), the 1,4-adduct was obtained from methyl 5-phenyl-2,4-pentadienoate (equation 3). Thus, it seems that the regioselectivity... 

Addition of hydrogen is selective for the double bond further from the electron-withdrawing group thus, the major alkene formed on selective reduction of ethyl 4-methyl-2,4-pentadienoate is the a,/3-unsaluralcd ester (equation 1). The reaction proceeds under mild conditions and in the presence of oxygen. 

Enamines undergo [4 + 2]cycloaddition with electrophilic alkenes such as ethyl sorbate, methyl 2,4-pentadienoate , penta-2,4-dienol , hexa-3,5-dien-2-... 

A few drops of coned, sulfuric acid added to a mixture of ethyl acetoacetate and triethyl orthoformate, stored 24 hrs., and neutralized with a slight excess of quinoline ethyl j -ethoxy-cis-crotonate (Y 89%) dissolved in dry ether, added to a suspension of 2 moles LiNHg in anhydrous liq. NHg, stirring continued 10 min., a soln. of benzaldehyde in dry ether added, stirred 1 hr., NHg replaced by ether, refluxed 5 min., and ice-water added 3-ethoxy-5-phenyl-cis-2-frans-4-pentadienoic acid (Y 74%). — Excess LiNHg is used to prevent self-condensation of the ester. F. e. s. E. E. Smissman and A. N. Voldeng, J. Org. Ghem. 29, 3161 (1964). 

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