Ethyl 3- propynoate

Diels-Alder cycloaddition of 3,4-bis(trifluoromethyl)furan with ethyl propynoate involved addition of two a,/3-unsaturated esters followed by acid-catalyzed ring opening, rearrangement, and elimination of ethanol to give a 6,7-bis(trifluoromethyl)isocoumarin-3-carboxylate [92JFC(56)359]. 

An attempt to introduce a bulky triphenylmethyl substituent at N-(y of methyl 677-furo[2,3-7]pyrrole-5-carboxylate 31a led to C-2 triphenylmethyl substitution giving the product 157, which with ethyl propynoate in acetonitrile gave the Michael addition product 158 <2000PJC207> (Scheme 16). 

Thus cyciobutadiene. which was nonexistent at the time, was shown to be stabilized by complexation. Oxidation of the complex liberated free cyciobutadiene which was trapped by ethyl propynoate to give a cycloadduct. The experiments established that... 

Similar, but not identical, behaviour is shown by ethyl propynoate in its reaction with the 4-hydroxypyran-2-one (75JCS(P1)2405). The differences are accounted for in terms of the relative instability associated with the cis configuration of the trans adduct (328), which... 

Oxidation of 6 with ceric iron, Ce(IV), releases cyclobutadiene which quickly dimerizes, but can be trapped by good dienophiles such as ethyl propynoate to give a cycloadduct. 

Further versatility of this approach has been realized with contrasting Lewis acid promoted additions of silyl ketene acetals, (191) to (194), to ethyl propynoate (Scheme 42). In fact, the tandem 1,4-conjugate addition-electrophile trapping protocol is feasible when titanium(IV) tetrachloride is employed. In situ functionalization of the intermediate titanate enoate (259), with select electrophiles, affords a-substituted enoates (260) to (262). On the other hand, the zinc iodide and zirconium(IV) tetrachloride protocols afford directly -y-alkoxycarbonyl-a-trimethylsilylenoates (263) and [2 + 2] adducts (264), respectively.100... 

To the ketene silyl (thio)acetal (1 equiv.) was added at room temperature neat ethyl propynoate, dimethyl acetylenedicarboxylate or etliynyl methyl ketone (1 equiv.). The mixture was stirred for 5 h at room temperature. The volatile products were removed at room temperature in vacuo (0.1 Torr) for 30 min. Purification of the crude reaction mixture by silica gel column chromatography (ethyl acetate-hexane, 5 95) afforded cycloadducts. 

See also Tris(trimethylsilyl)silane Ethyl propynoate... 

Cycloadditions of cyclic ketene trimethylsilyl acetals with ethyl propynoate and other electrophilic alkines were run at room temperature, without a catalyst and solvent-free [47]. 

The complexes 432 derived from the reaction of cinnamaldehyde with Ru-SH complexes 433 undergo [4+2] cycloaddition reactions with a range of electron-rich, electron-deficient, and strained dienophiles. The products are Ru complexes of di- or tri-substituted 3,4-dihydro-2/7-thiopyrans. Generally, the reaction shows high regioselectivity and good diastereoselectivity with a marked preference for the endo adducts (Scheme 139). Ethyl propynoate affords the 3,4-disubstituted-477-thiopyran <2006CEJ4821>. 

Thermolysis of the 1,3,4-oxathiazolines (130 R1 = Ar, X = O, Y = S) gives a ketone and a nitrile sulfide (see Section 4.34.3.4.1 Scheme 29). The latter can be trapped with DMAD to give isothiazoles (93) or with Et02CCN to yield 1,2,4-thiadiazoles (96 R2 = C02Et). Trapping with ethyl propynoate leads to a mixture of the two possible isomeric isothiazoles, their ratio (1.31-1.34) being apparently independent of R2, R3 and of the aryl substituent (80CC714) (compare with Section 4.34.3.2.6). 

Conjugate addition of /3-ketoesters or 1,3-diketones to ethyl propynoate leads to Michael adducts of type 8 which undergo radical cyclizations to furans in the presence of 2,2 -azobisisobutyronitrile (AIBN)/tributyltinhydride... 

Ethyl acrylate will react with vinylic cuprates, but at a much slower rate than a, -unsaturated ketones and ethyl propynoates 205). Complex-ation with trimethyl phosphite is advantageous because the reactivities of the cuprate and resulting carbanion are increased. Glutarate esters are important by-products from the reaction of the intermediate carbanion with another molecule of the acrylate the primary addition product was obtained in yields from 3.4% to 38% and the glutarate ester in 7.1-31% yield. 

Radical cyclization of divinyl ethers prepared from the reaction of 1,3-dicarbonyl compounds and ethyl propynoate gave rise to trisubstituted furans as shown in Ae following example <03TL2125>. 

Cyclobutenes possessing an angular O-functionality, obtained from a Lewis acid-mediated [2+2] cycloaddition of cyclic silyl enol ethers to ethyl propynoate and subsequent reduction and butenylation, undergo a ring-opening metathesis that produces a substituted dihydropyran that forms part of a c -diene. After desilylation, an oxy-Cope rearrangement leads to the fused tetrahydropyran 4 <03JA14901>. 

Several macrocyclic compounds have been prepared using Wittig reactions including tetraepoxyannulenes, which utilized the ylide derived from phos-phonium salt (57), and rotaxanes, molecules in which one or more macrocyclic components are trapped around a rod section of a dumbbell-shaped molecule, obtained by treating terephthaldehyde derivatives with dibenzylic bis(triphenyl-phosphonium)-stoppered [2]rotaxane (58). Aromatic triesters have been obtained by the (ethoxycarbonylmethylene)triphenylphosphorane-catalysedcyclo-trimerisation of ethyl propynoate. ... 

The high reactivity of iV-substituted pyridincs (review (1870]) is exemplified in the mild conditions needed to cyclize the A -allyiic side-chain of the pyridinium salt (42.1). Evidence for the participation of pyridinium ylides in this reaction is provided by adding ethyl propynoate and carbonate to the pyridinium salt [2469, 2471, 2518]. The pyridinium salt (42.2, R = Et) reacts with ketene dithioacetals (review [3712]) to give 3-substituted indolizines [2881] the behav-... 

Baylis-Hillman reaction. Ethyl propynoate apparently undergoes iodoalumination to generate a nucleophilic species that adds onto carbonyl compounds. (Z)- 3-Iodoacryhc esters are produced. ... 

Cycloaddition. Aldimines and those prepared in situ combine with ethyl propynoate readily. On applying the reaction to arylamines several quinoline-3-carboxylic esters have been prepared.The formation of l,4-dihydropyridine-3,5-dicarboxylic esters involves electrocyclic opening of the 1 1-cycloadducts and a Diels-Alder reaction. 

The reaction of (271 R = H, R = H or Me) with ethyl propynoate proceeded via Michael addition, to form (271 R = CH=CHC02Et), and subsequent rearrangement to the dihydronaphthalene (272). " 2-Benzoyl-aziridine (273) and RCH2C02Et (R = H or Ph) react in the presence of NaH to provide a novel synthesis of pyridinones (275). " The original objective of this study was the synthesis of the azabicyclo[3.1. Ojhexane (274), which was formed as an intermediate but not isolated from the reaction. 

Another case where the formation of the phosphane arm is the result of a Cp methyl C.H activation process is the reaction of bis(trimethylsilyl)derivative 240, which is closely related to 232, with 2 equiv of methyl or ethyl propynoate. The two propynoate units are coupled, and the unusually complex structures 243 and 244 are formed (Scheme 45). 243 has been the subject of an X-ray crystallographic investigation. Although the authors do not specifically comment on the stereochemistry, the fact that both compounds show one singlet in the P NMR spectrum indicates that 243 and 244 are formed diaste-reoselectively, presumably via 241 and 242. 

Reaction of the parent compound with ethyl propynoate gives a 1 1 mixture of 5- and 6-indolecarboxylate esters (Equation (147)) <90JCS(P1)2156>. 

Oxidation of (cyclobutadiene)tricarbonyliron with Ce in the presence of ethyl propynoate yielded a product corresponding to a Diels-Alder adduct of cyclobutadiene and ethyl propynoate. 

On the contrary, when 87a was reacted with ethyl propynoate, isocoumarins 262 were obtained. In this case the Diels-Alder cycloadduct 261 reacted as diene with another ethyl propynoate molecule. Tricyclic pyran underwent oxygen bridge opening followed by ethanol elimination presumably catalyzed by acidic Pyrex reaction tube walls [75, 78, 151]. Reaction of 110 with ethyl propynoate yielded complex mixture of unidentified products [78]. 

Abubakar AB, Booth BL, Tipping AE (1990) Novel Diels-Alder cycloaddition involving two a, p-unsaturated esters in the formation of isocoumaiins from the reaction of ethyl propyno-ate with 3,4-bis(trifluoromethyl)fhran. J HuorChem 47 353-359... 

The lithium acetylide salt of methyl or ethyl propynoate, prepared by treatment of the ester with n-butyl-lithium at low temperature, adds rapidly to a variety of aldehydes and ketones to give 4-hydroxyalk-2-ynoates. ... 

The reaction of pyrrole-l-carbodithioate with ethyl propynoate and benzoylacet-ylene (aqueous DMSO, KOH, room temperature, 2 h) leads to normal adducts, S-vinylpyrrole-l-carbodithioates in a low yield (10%-18%, Scheme 2.81, Table 2.9) [549,554]. Among the major reaction products are substituted divinyl sulfides as a mixture of E,E-, Z,E-, and Z,Z-isomers. 

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