Thiophene analogues of estrone; synthesis and structural assignment

Macrocyclization equilibrium data from metathesis reactions of cycloolefins (cyclobutene, cyclooctene, and cyclododecene) are compared with predictions of a novel, simple rotational isomeric state (RIS) scheme for polyalkenes with at least three single bonds between adjacent double bonds. The predictions agree with experiment within the combined experimental errors, supporting the conformational models and confirming that macrocyclization equilibrium has indeed been established in the metathesis reactions.

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Synthèse de polymères α,ω‐bifonctionnels par réaction de métathèse. Méthodologie d'approche des différences de réactivité des sites carbéniques en présence

Reyx

Campistron

1990

Makromol. Chem.

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The results of studies of co-metathesis reactions of 1,5-cyclooctadiene (1) with dimethyl 3-hexenedioate (2a) and for comparison, with 4-octene (2b) and 1,5-hexadiene (2c) are analyzed in order to approximate the relative reactivities of the carbene species and of the different types of double bonds. To this end, the experimental distributions of the first telomers are compared with theoretical ones calculated on the one hand allowing equal probability of arrangement of alkylidene groups and on the other hand allowing a kinetic control of propagation and transfer reactions. In other respects, the possibilities of mass control of the products obtained by the same co-metathesis or by degradation of 1,4-polybutadiene are studied. The results show that the reactivity of the 1,5-cyclooctadiene double bonds is higher than that of the other types of double bonds, this being in agreement with the hypothesis of stabilization of the 8-carbomethoxycarbene species by carbene/ester complexation. This stabilization allows us to explain the distribution of a,udifunctional oligomers in agreement with the hypothesis of kinetic control. The distribution of non-functional oligomers agrees with a random combination of alkylidene groups. This stabilization is compatible with the controlling method of molecular weights in the products obtained by polymerization of cyclooctadiene and also by degradation of 1,4-polybutadiene in the presence of 2a. @ 1990, Huthig & Wepf Verlag, Easel CCC 0025-1 16X/90/$03.00 Synthhe de polymeres a,mbifonctionnels par reaction de m6tathtse.. . 253 Schkmma 2: Distribution des oligomtres resultant d'une competition cinttique entre les rbctions de transfert aux composts ethylhiques 2 (constante de vitesse: ktn) et de propagation (constante de vitesse k,,) au cours de la ttlomtrisation du cycloditne 1. Expression des fractions molaires F, en oligomtres tl n motifs octtne-4 diylid&ne-1,8 en fonction du rapport R = [2]/[1] et des constantes de transfert C, (kt, /kp,,) 1 + 2 -, R'-CH=F(CHCH,CH,CH),+,,CH-R~ 4s-c R'-CH=CHCH,CH,CH=CHCH,CH,CH=W* Cl R~-CH+CHCH,CH,CH=CHCH,CH,CH~W* c 2 rkaction, variations d'autant plus importantes que les constantes de transfert C,, s'kloignent de l'unitk ne peuvent Stre prises en compte. L'Cvaluation des constantes de transfert A partir de la distribution des premiers oligomtres peut cependant permettre d'approcher les rkactivitks relatives d'une mCme esphce c a r b h e vis-A-vis des diffkrents types de doubles liaisons et la comparaison des rksultats obtenus pour diffkrents systhmes doit permettre d'approcher les rkactivitks relatives de diverses esphces carbhne.

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Thiophene analogues of estrone; synthesis and structural assignment

Cited by 12 publications

References 7 publications

ChemInform Abstract: THIOPHENE ANALOGS OF ESTRONE, SYNTHESIS AND STRUCTURAL ASSIGNMENT

ChemInform Abstract: THIOPHENE ANALOGS OF ESTRONE, SYNTHESIS AND STRUCTURAL ASSIGNMENT

Macrocyclization equilibria in polycycloolefins

Synthèse de polymères α,ω‐bifonctionnels par réaction de métathèse. Méthodologie d'approche des différences de réactivité des sites carbéniques en présence

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