Ethyl -but-2-enoate

Fischer-type carbenes are known as potential carbene transfer reagents to electron-rich and electron-deficient alkenes. Little is known about the chemistry of carbene complexes with silicon substituents at the carbene C-atom, whereas complexes with germanium, tin, or lead have not yet been prepared. The tungsten-carbene complexes 6 react with an excess of ethyl vinyl ether to give l,2-diethoxy-l-(trialkylsilyl)cyclopropanes 7." Only the f-isomers were formed and similar results can be achieved by using the corresponding molybdenum or chromium complexes. On the other hand, no reaction takes place with 2,3-dihydrofuran or ethyl ( )-but-2-enoate. ... 

The reaction between lithiated diethyl propenylphosphonate and ethyl propenoate leads to carbon-carbon bond formation involving either C(i) or C(3) of the phosphonate ester. Thus, ethyl but-2-enoate or but-3-en-2-one yielded 481 and 482, respectively, and the esters 483 were obtained from coumarin, all by simple addition, but addition-elimination and multiple addition processes were also described. 

The use of 3- or 4-picolylamine instead of benzylaminc with ethyl 4,4.4-trifluoro-3-oxobutanoate results in the expected (vide supra) rate acceleration in the isomerization of the corresponding enamines, analogs of 29a.15 Thus, ethyl 4,4,4-trifluoro-3-[(3-pyridylmethyl)-amino]but-2-enoate undergoes the enamine-azomethine-azomethine isomerization at room temperature in 36 hours to give the /J-(3-pyridylmethyleneamino) ester in 91 % yield. In the case of the 4-picolylamine derivative, complete isomerization occurs in 4 hours at room temperature to give the desired rearranged product in 86% yield.15... 

This reaction is considered in Sections 5.2.3, p. 496, and 5.18.2, p. 799, and the specific examples that are included in this section are (i) the formation of ethyl cyclohexylideneacetate from cyclohexanone and triethyl phosphonoacetate in the solvent 1,2-dimethoxyethane and using sodium hydride as the base for the formation of the phosphoryl-stabilised anion 254 and (ii) the formation of ethyl (E)-but-2-enoate from acetaldehyde and triethyl phosphonoacetate under PTC conditions255 (Expt 5.215). In the latter example the (E configuration is to be expected from the general features of the reaction that are summarised in Section 5.2.3, p. 496. 

C10H19O5P ethyl 2-(diethoxyphosphinyl)but-2-enoate 20345-62-4 408.1 35.134 2 21007 C10H20O 2-ethylhexyl vinyl ether 103-44-6 480.78 42.040 2... 

Figure 10.1.5. Mass spectra of tetraethyleneglycol dipropenoate MW = 302 (A) (from mass spectral libraries) and tentatively assigned spectra of 2-(2-prop-2-enoyl-oxyethoxy)ethyl prop-2-enoate MW =214 (B) and 2-(2-prop-2-enoyl-oxyethoxy)ethyl but-3-enoate MW = 228 (C).

Spin decoupling has been useful in identifying coupled pairs of nuclei. Figure 5-5 provides such an example for the molecule ethyl traw5-crotonate (ethyl fran.v-but-2-enoate). The alkenic protons split each other, and both are split by the allylic methyl group to form an ABX3 spin system. Irradiation at the methyl resonance frequency produces the upper spectrum in the inset for the alkenic protons, which have become a simple AB quartet. A more... 

In addition ethyl (Z)-2-(cyclopent-2-enyloxy)but-2-enoate (26 %) was formed. 

The photochemically induced fragmentation of esters 1 to vinylcarbenes by loss of ethene gives the corresponding cyclopropene in up to 40% yield after cyclization. For example, ethyl 3-(l-methylcyclopropyl)but-2-enoate gave ethyl 2,3-dimethylcycloprop-2-cnecarboxylate (R = = Me, R = H) in 40% yield but normally as one component of a mixture of several... 

Azomethine ylides, derived from condensation of ethyl ( )-4-(2-formy-laryloxy)but-2-enoates with various secondary amines, undergo intramolecular [3 + 2] cycloaddition reactions to provide polycyclic amine-fused chromans. This one-pot reaction is mediated by the combined action of benzoic acid and molecular sieves (Scheme 32) (14OL5910). 

Allylic halides can be useful synthetic precursors, as seen for reactions with ammonia. The reaction of 1.35 with diethylamine to give ethyl 4-(NJ4-diethyl-amino)but-2-enoate, 1.36. In this case the yield of 1J6 is moderate rather than high, but generally better than the identical reaction with ammonia (vide supra). A... 

Both ammonia and amines react with the carbonyl group. The reaction of dimethylamine and ethyl acetoacetate, for example, gave ethyl 3-(N,N-di-methylamino)but-2-enoate, /.72/. 0 Similar reaction with ammonia and ethyl acetoacetate gave methyl 3-aminobut-2-enoate in 90% yield. l... 

Dienoic acid derivatives such as 1.281 can be prepared by modification of other amino acids. The condensation of ethyl 3-(N-benzylamino)but-2-enoate 1.280) and ethyl propiolate gave ethyl 5-(N-benzylamino)-4-carboethoxyhexa-2Z.4E-dienoate. 1.281. Changing the 3-methyl group in the alkenyl amino acid to phenyl or hydrogen allowed the synthesis of other dienoic acid derivatives. In this study, the N-alkyl group was also modified from benzyl to hydrogen or methyLf ... 

A last example shows the reaction of a vinyl chloride such as 3.30 with ethylamine (see reaction 7). Addition of the amine generated the usual enolate anion intermediate, which displaced the P-chlorine to give a new conjugated ester. In this case, the product was ethyl 3-(N,N-diethylamino)but-2-enoate (3.57).23 The yield was relatively poor, but this example illustrates that conjugate addition of amines can lead to either the normal saturated product or, as in this case, an unsaturated amino acid. 

The reaction of S-phenethylamine and ethyl acetoacetate led to 5.209 (ethyl 3-(N-phenethyl)but-2-enoate)S9.90 as seen in chapter one, section l.l.C.ii. Reduction of the double bond would give the ethyl 3-aminobutanoate derivative, and the presence of the chiral auxiliary would lead to asymmetric induction during that reduction. 

Ethyl 3-(2-methyl-l//-mdol-3-yl)but-2-enoate (3a) Reaction time 3 h yield 76%... 

Ethyl 3-(benzylamino)but-2-enoate (3d) Semisolid reaction time 3 h yield 85%... 

Azide additions to a,P-unsatnrated systems are another method for the preparation of 1,2,3-triazoles. Cydoaddition of aryl azides to a,P-unsaturated aldehydes 88 in the presence of catalytic diethylamine and DBU afforded 1,4-disubstituted-l,2,3-triazoles 89 via an inverse electron-demand process (13CC10187). Michael addition of sodium azide with ethyhdene bisphospho-nates 90 in cydoaddition reactions via sonication afforded bisphosphono-1,2,3-triazoles 91 (13T4047).A one-pot protocol for the synthesis of 1,2,3-triazoles was prepared from unactivated alkenes with azidosulfenylation of the carbon-carbon double bond followed by the copper-catalyzed azide—alkyne cycloaddition (13JOC5031). 1,5-Disubstituted-l,2,3-triazoles 93 were synthesized from enamides 92 with tosyl azide (13AG(E)13265). Reaction of ethyl 3-(alkylamino)-4,4,4,-trifluoro-but-2-enoates 94 with mesyl azide in the presence of DBU afforded l,2,3-triazole-4-carboxylates 95 (13EJ02891). 

Zhou et al. have used the 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide for the microwave-assisted intramolecular Stetter reaction using imidazolium-type room temperature ionic liquids (RTILs) as solvents. The intramolecular Stetter reaction of ( )-methyl 4-(2-formylphenoxy) but-2-enoate was selected as a model to optimize the reaction conditions, using butylmethylimidazolium tetrafluoroborate [bmim]+[BF4]- as the solvent. It is known that salts of various heterocycles, including imidazolium salts, can also be used as catalysts. Therefore, the ionic liquids used as solvent is also able to function as a catalyst, even if it is less active than the usual thiazolium salts, and the yields of the desired product in that case are very poor. Subsequently, it was observed that when the quantity of thiazolium salt increased from 5 to 15 mol%, the yield improved accordingly to 96%. Under microwave irradiation, a variety of aromatic substrates undergo the intramolecular Stetter... 

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