Cycloaddition Of Ethyl Research Articles

Synthesis of ethyl 2-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-4H/2H-chromene-3-carboxylates by cycloaddition of ethyl 2-(azidomethyl)-4H-chromene-3-carboxylates with alkynes

The cycloaddition reaction has been carried out between ethyl 2-(azidomethyl)-4H-chromene-3-carboxylates and phenylacetylenes/ activated alkynes. Phenylacetylene, 4-fluorophenylacetylene were provided mixture of 2H- and 4H-triazolylchromene-3-carboxylates, whereas methyl, methoxyphenylacetylene and acetylenedicarboxylates were provided exclusively 2H-triazolylchromene-3-carboxylates. Interestingly, prop-2-yn-1-ol and ethyl propiolate were provided exclusively 4H-triazolylchromene-3-carboxylates.

Novel synthetic approach to non-natural conformationally rigid spiro-linked amino acids

1-Aminospiro[2.3]hexane-1,5-dicarboxylic and 1-ammo-5-(ammomethyl)spiro[2.3]hexane-1-carboxylic acids, which are the conformationally rigid analogues of glutamic acid and lysine, respectively, were synthesized from 3-methylidenecyclobutanecarbonitrile. The synthetic route includes a catalytic [1+2]-cycloaddition of ethyl 2-diazo-2-nitroacetate to a double bond of the unsaturated nitrile, a subsequent chemoselective reduction of the nitro and cyano groups, and a hydrolysis of the ester moiety.

Phosphine-catalyzed [3 + 2] cycloaddition of ethyl buta-2,3-dienoate to adamantane-containing N-substituted maleimides

Triphenylphosphine-catalyzed [3 + 2] cycloaddition between ethyl buta-2,3-dienoate and adamantane-containing N-substituted maleimides affords substituted bicyclic succinimides in excellent yields.

ChemInform Abstract: Ligand‐Free Cu‐Catalyzed [3 + 2] Cyclization for the Synthesis of Pyrrolo[1,2‐a]quinolines with Ambient Air as a Terminal Oxidant.

A ligand-free Cu-catalyzed [3 + 2] cycloaddition of ethyl 2-(quinolin-2-yl)acetates, ethyl 2-(isoquinolin-1-yl)acetates, and ethyl 2-(pyridin-2-yl)acetates with (E)-chalcones for a “one-pot” synthesis of pyrrolo[1,2-a]quinolines, pyrrolo[2,1-a]isoquinolines and indolizines has been developed. The annulation products were isolated in moderate to good yields with air as the sole oxidant under mild conditions.

Quinidine‐Catalysed Enantioselective Synthesis of 6‐ and 4‐Trifluoromethyl‐Substituted Dihydropyrans

The cinchona alkaloid‐catalysed enantioselective formal [4+2] cycloaddition of ethyl 2,3‐butadienoate with a range of 1,1,1‐trifluoro‐ and 4,4,4‐trifluorobutenones is investigated for the preparation of stereodefined 6‐ and 4‐trifluoromethyl‐substituted dihydropyrans. Quinidine proved to be the optimal catalyst, generating the desired products in up to 98 % ee and 81 % yield. Stereo‐ and chemoselective derivatization of the dihydropyrans through hydrogenation is explored.

Ligand-free Cu-catalyzed [3 + 2] cyclization for the synthesis of pyrrolo[1,2-a]quinolines with ambient air as a terminal oxidant.

A ligand-free Cu-catalyzed [3 + 2] cycloaddition of ethyl 2-(quinolin-2-yl)acetates, ethyl 2-(isoquinolin-1-yl)acetates, and ethyl 2-(pyridin-2-yl)acetates with (E)-chalcones for a "one-pot" synthesis of pyrrolo[1,2-a]quinolines, pyrrolo[2,1-a]isoquinolines and indolizines has been developed. The annulation products were isolated in moderate to good yields with air as the sole oxidant under mild conditions.

ChemInform Abstract: A Phosphine‐Catalyzed Regioselective [3 + 2] Cycloaddition of Ethyl 5,5‐Diarylpenta‐2,3,4‐trienoate with Aromatic Aldehydes and α,β‐Unsaturated Carbonyl Compounds.

AbstractA series of methylidene substituted 2,5‐dihydrofurans is prepared via the reaction of ethyl 5,5‐diphenylpenta‐2,3,4‐trienoate (I) with aryl or hetaryl aldehydes.

A Phosphine‐Catalyzed Regioselective [3+2] Cycloaddition of Ethyl 5,5‐Diarylpenta‐2,3,4‐trienoate with Aromatic Aldehydes and α,β‐Unsaturated Carbonyl Compounds

AbstractTributylphosphine‐catalyzed regioselective [3+2] cycloadditions between ethyl 5,5‐diarylpenta‐2,3,4‐trienoate 1 and various aromatic aldehydes 2 to produce a wide variety of polysubstituted 2,5‐dihydrofurans 3, and between 1 and β‐unsubstituted α,β‐unsaturated carbonyl compounds 5 to give polysubstituted cyclopentenes 6 with a quaternary carbon center, are reported. In both cases the reaction partners approach each other via the sterically less hindered orientation to afford the target products in excellent regioselectivity. The reaction mechanism involved first the generation of a zwitterionic intermediate between the butatriene 1 and PBu3. For the formation of 2,5‐dihydrofurans 3, the preferred cyclization mode encompassed the nucleophilic attack of the α‐position of butatriene to the aldehydic carbon of 2, followed by the ring closure between the aldehydic oxygen of 2 and the γ‐position of butatriene, which is the first report of a normal [3+2] cycloaddition between cumulenes and aldehydes. For the formation of cyclopentenes 6, the reaction involved attack of the γ‐position of the butatriene to the electron‐deficient β‐position of the α,β‐unsaturated carbonyl compounds 5, followed by the ring closure between the α‐position of 5 and the α‐position of butatriene, which shows a different regioselectivity to the previously reported [3+2] cycloadditions between butatriene and olefins.magnified image

Synthesis and unusual [2+2]-cycloaddition reactions of ethyl 4-chloro-2-oxobut-3-ynoate with unactivated alkenes

The highly activated acetylenes, ethyl 4-chloro-2-oxobut-3-ynoate and ethyl 4-bromo-2-oxobut-3-ynoate, were prepared from readily available bis(trimethylstannyl)acetylene in two steps with high overall yield. An unusual ability of the former to furnish [2+2]-cycloadducts with 1,1-disubstituted alkenes in the absence of irradiation and catalysts was discovered. The cycloaddition of ethyl 4-chloro-2-oxobut-3-ynoate to the 1,2-disubstituted alkenes was shown to be effectively catalyzed with stannic chloride.

Phosphine-Catalysed [3+2] Cycloaddition of Ethyl Buta-2,3-Dienoate and 4- uinolone-1,3-Dicarboxylate

Phosphine catalysed [3+2] cycloaddition, ethyl buta-2,3-dienoate. Allenes represent a class of highly useful organic build-ing blockes. The vicinal diene system is capable to undergo [2+2]-, [3+2]- and [4+2]-cycloaddition reactions [1]. Re-cently, a novel [3+2] annulation route for preparing cy-clopentenes and other derivatives, based on the phosphine-catalysed cycloaddition of buta-2,3-dienoates [4] and but-2-

Efficient Synthesis of Some Unsaturated [1,2,3]‐Triazole‐Linked Glycoconjugates

Thermal 1,3‐dipolar cycloaddition of ethyl 4‐azido‐2,3,4‐trideoxy‐α‐D‐erythro‐hex‐2‐enopyranosides with diethyl acetylenedicarboxylate or copper‐catalyzed reaction with various functionalized alkynes gave the corresponding 1‐(ethyl 2,3,4‐trideoxy‐α‐D‐erythro‐hex‐2‐enopyranosid‐4‐yl)‐1H‐1,2,3‐triazole derivatives in quite good yields. These unsaturated compounds could be transformed into 1‐(ethyl 2,3‐di‐O‐acetyl‐4‐deoxy‐α‐D‐mannopyranosid‐4‐yl)‐1H‐1,2,3‐triazoles by a simple dihydroxylation reaction. Copper‐catalyzed condensation of ethyl 6‐O‐acetyl‐4‐azido‐2,3,4‐trideoxy‐α‐D‐erythro‐hex‐2‐enopyranoside with 1,3,5‐triethynylbenzene or 1,3,5‐tris(prop‐2‐ynyloxy)benzene afforded the corresponding trivalent glycoconjugate clusters.

A Theoretical Study of the Stereoselectivities of the Diels–Alder Addition of Cyclopentadiene to Ethyl‐(S)‐lactyl Acrylate Catalyzed by Aluminium Chloride

AbstractWe have studied the AlCl3‐catalyzed cycloaddition of ethyl‐(S)‐lactyl acrylate (ELA) and cyclopentadiene (CPD) by MP2 and DFT (B3LYP) methods using the 6‐31G(d,p) basis set, with or without solvent effects. Four types of dienophile–Lewis acid (LA) complexes were considered — two types of ELA·AlCl3, ELA·2AlCl3 and ELA·AlCl2+. The stereochemical predictions of these models were compared with available experimental data. The participation of lactate‐bound ELA·AlCl3 complexes is insignificant because of their relatively high TS energies. The diastereofacial selectivities exhibited by the chelated ELA·AlCl2+ complex do not agree with experimental data, suggesting that this type of complex is not very probable, even with ligands having an appropriate carbonyl orientation. Our results show the dominating role of ELA·2AlCl3 in the catalyzed reaction, in agreement with experimental data. The observed diastereofacial stereoselectivities are due to a delicate equilibrium of electrostatic and steric interactions in the different transition states between the two LA groups and between these two groups and the cyclopentadiene moiety. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

1,3-Dipolar Cycloaddition of Ethyl 2,3-Pentadienoate with Pyridinium Dicyanomethylides: Regiospecific Formation of Ethyl 3-Cyano-2-ethylindolizine-1-carboxylates and a Novel Formation of Tricyclic Compounds

Pyridinium dicyanomethylides underwent site- and regioslective 1,3-dipolar cycloaddition with ethyl 2,3-pentadienoate to give ethyl 3-cyano-2-ethylindolizine-1-carboxylates in moderate yields. In two cases, a novel type of the tricycle compounds, in addition to indolizines, were obtained whose structure was established by a single crystal X-Ray analysis. A plausible mechanism for its formation is also presented.

Synthesis of Thienobenzofuranquinone Derivatives by Photoinduced and CAN-mediated 3+2-Type Cycloaddition Reactions

Photoinduced cycloaddition between ethyl 5-hydroxy-3-methyl-4,7-dioxo-4,7-dihydrobenzo[b]thiophene-2-carboxylate (la) and alkenes is reported to give ethyl 7-methyl-4,8-dioxo-2,3,4,8-tetrahydrothieno[2,3-f]benzofuran-6-carboxylates (2). Cerium(IV) ammonium nitrate (CAN)-mediated cycloaddition of ethyl 5-hydroxy-4,7-dioxo-4,7-dihydrobenzo[b]thiophene-2-carboxylates (1) to alkenes or phenylacetylene, giving ethyl 4,8-dioxo-4,8-dihydrothieno[2,3-f]benzofuran-6-carboxylate (2 or 4) and ethyl 4,5-dioxo-4,5-dihydrothieno[3,2-g]benzofuran-7-carboxylate derivatives (3 or 5), is also reported.

Synthesis of 5‐fluoroalkyl lsoxazolidines via 1,3‐dipolar cycloaddition of ethyl 2‐hydropolyfluoroalk‐2‐enoates with nitrones

Abstract1,3‐Dipolar cycloaddition reactions of ethyl 2‐hydropolyfluoroalk‐2‐enoates (1) with some nitrones were described. The reaction of 3,4‐dihydroisoquinoline N‐oxide (2) with 1 took place readily in methylene chloride at room temperature to give the corresponding 5‐fluoroalkylisoxazolidines regioselectively as a mixture of two diastereoisomers (trans and cis) in high yields, while longer reaction time and higher temperature were needed in the case of non‐cyclic nitrones. Under similar conditions the reaction of quinoline N‐oxide (14) with 1 did not give the expected adducts and a ring‐opening product was obtained.

The 1,3-dipolar Cycloaddition of Ethyl N-(ethoxycarbonylmethyl)benzimidate with N-aryl maleimides

1,3-Dipolar cycloaddition of ethyl N-(ethoxycarbonylmethyl)benzimidate (1) with N-aryl maleimides (2) gave a pair of pyrrolo[3,4- c]pyrrole isomers (3, 4) and a 7-azabicyclo[2.2.1]heptane derivative (5). The configuration of isomers 3 and 4 was confirmed by 1H-NMR.

Regiospecific Syntheses of the Monomethylated 3-Phenyldihydro-1,2,4-triazin-6(1H)-ones

Unambiguous syntheses of four unreported monomethylated derivatives of 3-phenyldihydro-1,2,4-triazin-6(1H)-ones, namely, the 1-methyl (2), 2-methyl (3), 4-methyl (4) and the imidic O-methyl derivative (5), are described. Regioselectivity was achieved for the synthesis of (2) by addition of ethyl glycinate to the 1,3-dipolar nitrile imine derived from N- methylbenzohydrazonoyl bromide hydrobromide (8). The key step for the synthesis of (3) was addition of benzyl 3-methylcarbazate (14) to ethyl N-[ chloro (phenyl) methylene ] glycinate (15b). The 4-methyl compound (4) was prepared by cycloaddition of ethyl N-( thiobenzoyl ) sarcosinate (21) with hydrazine hydrate, and the O-methyl compound (5) was prepared by reaction of sodium methoxide with 6-chloro-3-phenyl-4,5-dihydro-1,2,4-triazine (23).

ChemInform Abstract: Synthesis of Esters of Lipophilic Proline Analogs by Reduction of Ethyl 5,6‐Dihydro‐4H‐1,2‐oxazine‐3‐carboxylates.

AbstractThe dihydro‐1,2‐oxazine derivatives (III) are obtained by cycloaddition of ethyl 2‐nitrosopropenoate, prepared in situ from the bromohydroxyiminopropanoate (II), with the enamines (I).

A synthesis of geminally functionalized heterocyclic aminocarboxylic acids by cycloaddition of ethyl N-acetyl-α,β-dehydroalaninate with 1,3-dipoles

1,3-Dipolar cycloaddition of α,β-dehydroalaninate with dipoles proceeded with high regioselectivity to afford the title compounds in good yields.