Ozonolysis of Highly Methylated 1,2-Bis(methylene)cycloalkanes. Influence of the Methyl Substituents on the Course of the Reaction
摘要:
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.
1,6-Dibromotricyclo[3.1.0.02,6]hexane 2e has been prepared in 56% yield by reaction of 1,6-dilithiotricyclo[3.1.0.02,6]hexane 2d with 2.5 equiv. of tosyl bromide. 2e proved to be a new source for generating tricyclo[3.1.0.02,6]hex-1-(6)-ene 1 by reaction with magnesium, with lithium sand, or with tert-butyllithium, as shown by formation of the Diels-Alder adduct 5. Ene adducts of 1 were obtained with
An efficient synthesis of the title compound 14 is reported, which employs the ZnCl2/Et2O catalyzed addition of acetyl chloride (4) to 2-methyl-2-butene (5) and the [3+ + 2] cycloaddition of the 1,1,2,3-tetramethylallyl cation to 2,3-dimethyl-2-butene as key steps.
报告了标题化合物14的有效合成,该化合物使用ZnCl 2 / Et 2 O催化的乙酰氯(4)加到2-甲基-2-丁烯(5)上,并[3 + + 2]环加成。 1,1,2,3-四甲基烯丙基阳离子生成2,3-二甲基-2-丁烯为关键步骤。
Acceleration of diels-alder reactions by remote methyl groups
作者:Janusz Baran、Herbert Mayr
DOI:10.1016/s0040-4020(01)81013-9
日期:1989.1
The hexamethyl substituted bismethylenecyclopentane 1a is 4 to 7 times more reactive towards the acetylenic dienophiles 2 and 3 than the nonmethylated 1,2-bismethylenecyclopentane 1b. This unusual consequence of branching is explained in terms of steric and electronic effects.