Carbon‐13 n.m.r. spectra of 2,3‐dimethylenebicyclo[2.2.1]heptanes and 2,3‐dimethylene‐7‐oxabicyclo[2.2.1]heptanes

Quarroz, Daniel; Sonney, Jean-Marie; Chollet, André; Florey, André; Vogel, Pierre

doi:10.1002/mrc.1270091102

Cited by 34 publications

(8 citation statements)

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“…For instance the I3GNMR. characteristics of 6[21] and 10[I], as well as their Diefs-Alder reactivity toward tetracyanoethylene[ I ] are better explained by considering the electron-withdrawing effect of…”

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confidence: 99%

Regioselectivity of the Diels‐Alder Additions of 2‐Substituted 5,6 Dimethylidenenorbornanes and‐bicyclo[2.2.2]octanes

Avenati

Carrupt

Quarroz

et al. 1982

Helvetica Chimica Acta

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SummaryThe cycloadditions of methyl propynoate and methyl vinyl ketone to 5,6-dimethylidene-2-norbornanone (6) are 'para 'regio~elective~). A smaller 'para Lregioselectivity is observed for the addition of methyl propynoate to 5,6-dimethylidene-2-bicyclo[2.2.2]octanone (10). No regioselectivity is observed with 5,6-dimethylidene2exo-norbornyl alcohol (3), acetate (5) and 5,6-dimethylidene-2 exo-bicyclo[2.2.2]0~-tanol(9). PMO arguments based on the shape of the HOMO'S and subHOMO's of the dienes allow to rationalize these observations. Unpredictable 'para-or 'metat regioselectivities are found for the Diels-Alder additions of 5,6-dimethylidene-2en-do-norbornyl alcohol (2), acetate (4) and 5,6-dirnethylidene-2endo-bicyclo[2.2.2]0~-tanol(8). The carbonyl group ofP,y-unsaturated ketones such as 6 and 10 can act as an electron donating homoconjugated substituent. The n(CO)++o[C( l),C(2)]t+x [C(5),C(6)] hyperconjugative interaction can override the usual electron-withdrawing effect of this function. ~~Introduction. -The Diels-Alder reactivity of an exocyclic s-cis-butadiene6) grafted onto norbornane [2] [3] and bicyclo[2.2.2]octane [ 11 [4] skeletons (s. 1 and 7, resp.) can be affected by remote substitution of the bicyclic systems. The carbonyl group in 5,6-dimethylidene-2-norbornanone (6) and in 5,6-dimethylidene-2-bicycIo[2.2.2]0~-tanone (10) causes a significant rate retardation effect on the cycloadditions of the diene to strong dienophiles. We report now on the regioselectivity of the Diels-Alder additions of the homoconjugated dienones 6 and 10, and of the related endo-and exo-alcohols 2,8, 3 and 9, and acetates 4 and 5.Since our exocyclic dienes are grafted onto rigid bicyclic skeletons, geometry and steric factors should not play a dominant role in determining the regioselectivity

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confidence: 99%

Regioselectivity of the Diels‐Alder Additions of 2‐Substituted 5,6 Dimethylidenenorbornanes and‐bicyclo[2.2.2]octanes

Avenati

Carrupt

Quarroz

et al. 1982

Helvetica Chimica Acta

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“…The carbonyl group in 5,6-bis (methylidene)-2-norbornanone (4) caused, however, a significant rate retardation effect, although not as large as that observed for exo-2,3-epoxy-5,6-bis (methy1idene)-norbornane (5), relative to the parent diene 1. These observations suggested that the effect caused by the epoxide ring in 5 on the chemical and spectroscopic properties of this exocyclic diene [9] were probably the manifestations of strain introduced into the bicyclic skeleton and/or specific electronic features (ie., low-lying empty orbitals, electrophilicity) of the oxirane ring [2]. To a first approximation, the strain introduced by the epoxy substituent in 5 must be the same as that introduced by the cyclopropane ring [lo] in the exo-6,7-bis (methy1idene)-tricyclo [3.2.1 .02,4]-octane (6).…”

Section: The Effects Of Homoconjugated Cyclopropane and Oxirane Ringsmentioning

confidence: 97%

The Effects of Homoconjugated Cyclopropane and Oxirane Rings on the Diels‐Alder Reactivity of 2,3‐bis (methylidene)norbornane

Pilet

Chollet

Vogel

1979

Helvetica Chimica Acta

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SummaryPreparation of 6ex0,7exo-bis (methy1idene)-tricyclo [3.2. 1.02.4]octane (6) is described. The reactivity of 6 towards tetracyanoethylene is evaluated and compared with that of ex0-2,3-epoxy-5,6-bis (methy1idene)norbornane (5), 2,3-bis-(methy1idene)norbornane (1) and other related dienes. The cyclopropane group in 6 exerts an unsignificant rate retardation effect on the Diels-Alder reactivity of this diene relative to that of 1, whereas a relatively important rate retardation effect is caused by the exo-oxirane ring in 5. The observed effects are probably due to electronic factors (through-space and through-bond interactions).Introduction. -Chemical and spectroscopic properties of the s-cis-butadiene function in 2,3-bis (methy1idene)norbornane (1) can be modified without direct

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“…13C-NMR. spectra of 5,6-dimethylidene-7-oxanorborn-2-ene and derivatives [30]); 132.7 (br.s, C(5a,9a)); 128.9 (br. d, IJcH= 156, C (7,8)); 125.9 ( d x m , (26), 193 (IOO), 179 (19), 178 (26), 170 (18).…”

Section: )mentioning

confidence: 99%

ChemInform Abstract: ANTHRACYCLINONES. PART II. SYNTHESIS OF (.+‐.)‐4‐DEMETHOXYDAUNOMYCINONE BY DOUBLE DIELS‐ALDER ADDITIONS TO 2,3,5,6‐TETRAMETHYLIDENE‐7‐OXANORBORNANE

Bessière¹,

Vogel²

1980

Chemischer Informationsdienst

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SummarySequential Diels-Alder additions of methylvinyl ketone and dehydrobenzene to 2,3,5,6-tetramethylidene-7-oxanorbornane (4) yielded the (5,12-epoxy-1,2,3,4,5,6,11,12-octahydro-2-naphtacenyl)methyl ketone (10) which, in few steps was oxidized to a precursor of ( k )-4-demethoxydaunomycinone. The preparations of two precursors of anthracyclinones, the (5-acetoxy-) and (12-acetoxy-1,2,3,4-tetrahydro-2-naphtacenyl)methyl ketones (14,15) are presented. The synthesis of 6,13-epoxy-6,13-dihydropentacene (8) is also reported.

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Carbon‐13 n.m.r. spectra of 2,3‐dimethylenebicyclo[2.2.1]heptanes and 2,3‐dimethylene‐7‐oxabicyclo[2.2.1]heptanes

Abstract: The I3C n.m.r. spectra of 11 derivatives of 2,3-dimethylenenorbornane, 1-11, of 5 derivatives of 2,3-dimethylene-7-oxanorbornane, 12-16, and of 2,3,5,6-tetramethylene-7-oxanorbornane (

Cited by 34 publications

References 50 publications

Regioselectivity of the Diels‐Alder Additions of 2‐Substituted 5,6 Dimethylidenenorbornanes and‐bicyclo[2.2.2]octanes

Regioselectivity of the Diels‐Alder Additions of 2‐Substituted 5,6 Dimethylidenenorbornanes and‐bicyclo[2.2.2]octanes

The Effects of Homoconjugated Cyclopropane and Oxirane Rings on the Diels‐Alder Reactivity of 2,3‐bis (methylidene)norbornane

ChemInform Abstract: ANTHRACYCLINONES. PART II. SYNTHESIS OF (.+‐.)‐4‐DEMETHOXYDAUNOMYCINONE BY DOUBLE DIELS‐ALDER ADDITIONS TO 2,3,5,6‐TETRAMETHYLIDENE‐7‐OXANORBORNANE

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