1-Ethyl-l-methylcyclopentane

Another convoluted example is similar to the analysis of 26. Cyclic alkane 27 could be named l,l-dibromo-3-ethyl-4-methylcyclopentane, l,l-dibromo-4-ethyl-3-methylcyclopentane, 3,3-dibromo-l-ethyl-5-methylcyclopentane, 4,4-dibromo-l-ethyl-2-methylcyclopentane, 3,3-dibromo-5-ethyl- 1-methylcyclopentane, or 4,4-dibromo-2-ethyl-l-methylcyclopentane. The lowest combination of numbers is either l,l-dibromo-3-ethyl-4-methylcyclopentane or l,l-dibromo-4-ethyl-3-methylcyclopentane, but this choice leads to another dilemma because it coidd be 3-ethyl-4-methyl or 4-ethyl-3-methyl. To distinguish the latter, rely... 

Ethyl-1-methylcyclopentane c/5-1-Ethyl-2-methylcyclopentane fra/ s-1-Ethyl-2-methylcyclopentane c/>1-Ethyl-3-methylcyclopentane //a/JS-l-Ethyl-S-methylcyclopentane... 

A modification of this method utilizes the direct conversion of l,2-bis(trimethyl-siloxy)cyclobutene in one step to 2,2-disubstituted cyclopentane-1,3-diones. For example, 2-ethyl-2-methylcyclopentane-l,3-dione (3) was obtained in 91% yield from 1.2-bis(trimethyl-siloxy)cyclobutene and butan-2-one 2,2-dimethylpropane-l,3-diyl acetal.41 Further examples... 

Methyl- 1,3-cyclopentanedione is a key intermediate for the total synthesis of steroids.2 A number of methods have been described for its preparation, among them the condensation of succinic acid with propionyl chloride,3 and that of succinic anhydride with 2-buten-2-ol acetate,4 both in the presence of aluminum chloride. It has also been obtained from 3-methylcyclopentane-1,2,4-trione by catalytic hydrogenation5 and Wolff-Kishner reduction 6 The base-promoted cyclization of 4-oxohexanoic acid ethyl ester and diethyl propionylsuccinate with tertiary alkoxides was first reported by Bucourt.7 The present cyclization process provides an experimentally simple route to 2-methyl-1,3-cyclopentanedione. Using the same procedure, 4-oxoheptanoic acid ethyl ester has been cyclized to give 2-ethyl-l,3-cyclopentanedione in 46% yield... 

Methyl-l-ethylcyclopentane mixed with less than 5% of 1-methyl-cis-3-ethylcyclopentane was obtained in 26% yield by the ethylation of methylcyclopentane (Expt. 9). The presence of methyldiethylcyclopentane and methylbutylcyclopentane in the higher molecular weight by-product was suggested by gc coupled with ms. 

D.74) 2-Cyclopenten-l-one, 3-ethyl-2-hydroxy-4-methyl-, 3-ethyl-2-hydroxy-4-methylcyclopent-2-en-l-one [42348-12-9] FEMA 3453 1,2-cyclopentanedione, 3-ethyl-4-methyl-, 3-ethyl-4-methylcyclopentane-1,2-dione... 

D.77) 2-Cyclopenten-l-one, 4-ethyl-2-hydroxy-3-methyl-, 4-ethyl-2-hydroxy-3-methylcydopent-2-en-I-one [71387-71-8] 1,2-cyclopentanedione, 4-ethyl-3-methyl-, 4-ethyl-3-methylcyclopentane-l,2-dione... 

Arts. In the order given, left to right, the compounds are cyclohexane, methylcyclopentane, ethylcyclo-butane, 1,2-dimethylcyclobutane, 1,3-dimethylcyclobutane, 1,1-dimethylcyclobutane, n-propyl-cyclopropane, isopropylcyclopropane, 1-ethyl-1-methylcyclopropane, l-ethyl-2-methylcyclopropane, 1,2,3,-trimethylcyclopropane. 

The presence of by-products such as 1-chloro-ethyl acetate 3 and a small amoimt of ethyl acetate, suggests that the initial step is an intermolecular hydride ion transfer from cyclohexane or methylcyclopentane towards acetyl chloride-aluminium chloride complex to give 1-methylcyclopentene. From cyclohexane, the cyclohexyl cation isomerizes to 1-methyl-l-cyclopentyl carbenium ion which loses a proton. Then, the 1-chloro-ethylate-aluminium chloride... 

Azasteroids.p-Toluenesulfonic acid added to a soln.of2-[2 -(l,2,3,4-tetrahydro-7-methoxy-N-tosyl - 4 - quinolylidene) ethyl] -2 - methylcyclopentane-1,3 - dione in benzene, and gently refluxed 10 min. at an oil bath temp, of 100-110° dl-N-tosyl-6-azabisdehydro-8,14-estrone methyl ether. Y 75%. H. O. Huisman, W. N. Speckamp, and U. K. Pandit, R. 82, 898 (1963). 

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