Synthesis of Some 3-Substituted-2,4-dimethyl-1,3-pentadienes<sup>1</sup>

Warner, Philip; Le, Diem Duy

doi:10.1080/00397918408057673

Cited by 10 publications

(1 citation statement)

References 13 publications

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“…Among 10 primary and 5 secondary products of reactions of 2a and 2b with RLi, 5 were isolated in their pure forms. The remaining compounds were analyzed as mixtures, and their structural assignment was based on MS and NMR spectra, comparison with literature NMR spectra (12b, 15, and 16), or close match with analogous cyclopropane derivatives [53][54][55][56] (bromine-containing derivatives, 2, 7, 8, and also 9a; details in the Supporting Information). Further support for the structural assignment to the observed products that do not contain bromine (9a, 10a (R ) Me, Ph, t-Bu), 11, and 12) was provided by comparison of the DFT-calculated and experimental 1 H and 13 C NMR chemical shifts (Figure 8).…”

Section: Carbenementioning

confidence: 99%

Reactivity of 13,13-Dibromo-2,4,9,11-tetraoxadispiro[5.0.5.1]tridecane toward Organolithiums: Remarkable Resistance to the DMS Rearrangement

et al. 2008

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Reactions of dibromocyclopropane 2a, containing two spiro-fused 1,3-dioxane rings, with MeLi gave only the methylation products 8 and 9 even at elevated temperatures. In contrast, the cyclohexane analogue 2b treated with MeLi underwent a smooth rearrangement to bicyclo[1.1.0]butane 11b at -78, -10, or +35 degrees C. Treatment of 2a with PhLi gave the alpha-Ph anion 13 as the only product, which underwent smooth methylation with MeI to give 14. Under the same conditions, 2b with PhLi gave bicyclo[1.1.0]butane 11b accompanied by bromophenyl derivative 8b. Treatment of either dibromide with t-BuLi gave a mixture of products including debrominated cyclopropanes 12. Experimental results were augmented with DFT calculations for salts 23 and MP2//DFT-level calculations for carbenes 22. They demonstrated a higher stability of the dioxane alpha-bromo anion with respect to alpha-elimination by 4.8 kcal/mol and also a lower tendency of the carbene 22a to undergo rearrangement by 4.0 kcal/mol than the cyclohexane analogues. These differences have been attributed to the inductive effect of the four oxygen atoms, which results in lower LUMO energy, the higher positive charge at the carbenic center, and the overall more electrophilic character of carbene 22a as compared to the cyclohexane derivative 22b. The rearrangement of carbenes 22 to the corresponding allenes 1, the thermodynamic products, requires a higher activation energy DeltaG(double dagger)(298) by 4.2 kcal/mol for dioxane and 6.4 kcal/mol for cyclohexane derivatives than for the formation of the bicyclo[1.1.0]butanes 11. The DeltaG(double dagger)(298) for intramolecular insertions to the CH bond is low and calculated as 6.0 kcal/mol for dioxane 22a and 2.0 kcal/mol for the formation of cyclohexane 22b.

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Section: Carbenementioning

confidence: 99%

Reactivity of 13,13-Dibromo-2,4,9,11-tetraoxadispiro[5.0.5.1]tridecane toward Organolithiums: Remarkable Resistance to the DMS Rearrangement

et al. 2008

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Blitzvakuumthermolyse von 1‐Chlor‐4‐methylen‐spiro[2.m]alkanen

1986

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Flash Vacuum Thermolysis of l-Chloro-4-metbyleoespiro[2.m]alkanesThe title compounds 5 were prepared by addition of bromochlorocarbene to 1,2-bis(methy1ene)cycloheptane (3a) and -cyclohexane (3 b), respectively, to give 4, followed by reduction with triphenyltin hydride. Flash vacuum thermolysis of 5 gave instead of the expected vinylcyclopropane rearrangement to the chlorocyclopentenes 8 the halogen-free trienes 7 (80-90% yield), which were characterized by their spectra and by Diels-Alder reaction with tetracyanoethene to the adducts 6. The mechanism of formation of 7 is discussed. Bei der Blitzvakuurnthermolyse der Diastereomerengemische von 5 bei 600°C und 0.04 mbar erwarteten wir in Analogie zu der sehr spezifischen Umlagerung von 1 zu 2 das 4Chlorcyclopentenderivat 8. Diese Verbindungen hatten wir bereits auf anderem Wege 0 VCH Verlagsgesellschaft mbH, D

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ChemInform Abstract: Synthesis of Some 3‐Substituted 2,4‐Dimethyl‐1,3‐pentadienes.

Warner¹,

Le²

1986

Chemischer Informationsdienst

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Synthesis of Some 3-Substituted-2,4-dimethyl-1,3-pentadienes¹

Cited by 10 publications

References 13 publications

Reactivity of 13,13-Dibromo-2,4,9,11-tetraoxadispiro[5.0.5.1]tridecane toward Organolithiums: Remarkable Resistance to the DMS Rearrangement

Reactivity of 13,13-Dibromo-2,4,9,11-tetraoxadispiro[5.0.5.1]tridecane toward Organolithiums: Remarkable Resistance to the DMS Rearrangement

Blitzvakuumthermolyse von 1‐Chlor‐4‐methylen‐spiro[2.m]alkanen

ChemInform Abstract: Synthesis of Some 3‐Substituted 2,4‐Dimethyl‐1,3‐pentadienes.

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Synthesis of Some 3-Substituted-2,4-dimethyl-1,3-pentadienes1

Cited by 10 publications

References 13 publications

Reactivity of 13,13-Dibromo-2,4,9,11-tetraoxadispiro[5.0.5.1]tridecane toward Organolithiums: Remarkable Resistance to the DMS Rearrangement

Reactivity of 13,13-Dibromo-2,4,9,11-tetraoxadispiro[5.0.5.1]tridecane toward Organolithiums: Remarkable Resistance to the DMS Rearrangement

Blitzvakuumthermolyse von 1‐Chlor‐4‐methylen‐spiro[2.m]alkanen

ChemInform Abstract: Synthesis of Some 3‐Substituted 2,4‐Dimethyl‐1,3‐pentadienes.

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Synthesis of Some 3-Substituted-2,4-dimethyl-1,3-pentadienes¹