Synthesis of 1,1,2,2,3,3-hexamethyl-4,5-bis(methylene)cyclopentane

Baran, Janusz; Klein, Herbert S.; Schade, Christian; Will, Elfriede; Koschinsky, R.; Bäuml, Englbert; Mayr, Herbert

doi:10.1016/s0040-4020(01)81725-7

Cited by 14 publications

(6 citation statements)

References 10 publications

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“…1 H and 13 C NMR spectra were taken on JEOL JNM-EX 270 MHz or JNM-PS 100 MHz spectrometer in CDCl 3 (unless otherwise noted) with SiMe 4 as standard. Dienes 1a , 1b , 1c , and 1d 12 were prepared by the reported methods. Ozonolyses were carried out with a Nippon Ozone Model ON-1-2 ozonator; dry oxygen containing about 2% of ozone was introduced at a speed of 50 L/h in the solution of the substrate.…”

Section: Methodsmentioning

confidence: 99%

Ozonolysis of Highly Methylated 1,2-Bis(methylene)cycloalkanes. Influence of the Methyl Substituents on the Course of the Reaction

et al. 1996

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In the ozonolyses of highly methylated 3,3,4,4,5,5-hexamethyl-1,2-bis(methylene)cyclopentane (1a) and 3,3,6,6-tetramethyl-1,2-bis(methylene)cyclohexane (1b), the epoxidation competed with the cleavage of the C−C double bond, whereas only the latter process was observed in the case of the nonmethylated 1,2-bis(methylene)cycloalkanes 1c,d. Competition experiments revealed that the reactivity of the highly methylated 1,2-bis(methylene)cycloalkanes 1a,b is significantly smaller than that of the nonmethylated ones (1c,d), suggesting that the formation of the primary ozonides 2c,d occurs by a concerted 1,3-dipolar cycloaddition process.

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Section: Methodsmentioning

confidence: 99%

Ozonolysis of Highly Methylated 1,2-Bis(methylene)cycloalkanes. Influence of the Methyl Substituents on the Course of the Reaction

et al. 1996

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“…Portions (0.2 mL) of the solution of 1, n-C^H^(as internal GC standard), and (a) bis (3-tert-butyl-4-hydroxy-5-methylphenyl) sulfide (BHMPS) or (b) diphenylamine (Ph2NH) (as inhibitors of radical chain polymerization of 1) in toluene (degassed and saturated with argon) were sealed in PTFE tubes (pretreated with refluxing triethylamine in order to avoid acid catalysis at the surface of the PTFE tubes), placed in a 10-kbar autoclave, and heated at different pressures as stated in Table III. The degree of conversion and the product ratio [3]: [4] were analyzed by GC, using a Sichromat 2 (Siemens). Column: silicon oil OV 1 25 m fused silica.…”

Section: Methodsmentioning

confidence: 99%

“…(7) 5* and AAH* result from the temperature dependence of the product ratio [3]: [4] measured by GC very precisely.…”

mentioning

confidence: 99%

Stepwise [4 + 2]- and [4 + 4]-cyclodimerizations of 1,1,2,2,3,3-hexamethyl-4,5-bis(methylene)cyclopentane

Baran¹,

Mayr²,

Ruster³

et al. 1989

J. Org. Chem.

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Solvent Dependence of the Product Ratio from la and 5. The reaction was carried out with equimolar amounts of la and 5 a t ambient temperature in different solvents as described for ether (see above).lg The crude product mixture was analyzed by 'H NMR using the singlets at 6 5.04 and 5.07 for 8, the singlets at 6 5.58 and 6.43 for 9, and the singlet at 6 6.09 for 10. The small (CDCl,) 6 22.12 (t), 31.10 (t), 40.01 (t), 45.14 (t), 92.78 (s), 108.50The deviation of the 8:9:10 product ratio (ether) from that reported above is due to the use of la and 5 in a 1:l ratio (2:l in the previous experiment), which reduces the probability of the sequential reaction of la with 9 to give 10.amounts of 11 have been neglected. Relative Reactivities of Dipolarophiles toward Benzonitrile Oxide (la). A mixture of two dipolarophiles and benzohydroxamoyl chloride were dissolved in 4 mL of CClb Triethylamine was added, and the mixture was stirred a t 20.5 OC for 8 h. The mixture was filtered to remove triethylammonium hydrochloride, and the filtrate was concentrated under reduced pressure to give a mixture of products, which was analyzed by 'H NMR or GC.The The thermal dimerization of the title compound 1 yields the [4 + 21-cyclodimer 3 and the [4 + 41-cyclodimer 4 in a ratio of approximately 3.5:l. Comparison of activation enthalpies ( " ( 3 ) = 80.1 kJ/mol, "(4) = 76.6 kJ/mol) and activation entropies (LS'(3) = -143.1 J/mol K, AS'(4) = -163.3 J/mol K) indicates both cycloadditions

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“…109 The sterically more encumbered 2-methyl-2-butene 198 proved to be a suitable Friedel-Crafts acceptor in the reaction with AcCl 199, both under AlCl 3 88 (Scheme 50) and ZnCl 2 catalysis (Scheme 58). 110 Via the latter protocol, however, an appreciable amount of dehydrochlorinated product 201 was formed. Besides, the addition of several acid chlorides to cyclohexene has been reported (see also Stereochemical Considerations).…”

Section: Friedel-crafts Acylation Of Alkenesmentioning

confidence: 99%

“…According to a direct comparison made by Mayr and co-workers, however, the acylation of the sterically hindered 2-methyl-2-butene 198 proceeded in significantly lower yield with Ac 2 O 252 than when using AcCl 199 (Scheme 64). 110 Still, Dubois and co-workers reported that treatment of cyclohexene with Ac 2 O in the presence of ZnCl 2 does not yield 1-acetyl-2-chlorocyclohexane in a straightforward manner, but rather as one of five products formed during the reaction. 91 Stereochemical Considerations.…”

Section: Friedel-crafts Acylation Of Alkenesmentioning

confidence: 99%