ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Syntheses and Thermolyses of 1-Alkynyl-2-methyl-1,2-epoxy-cycloalkanes. - Attempts at Ring Enlargement by Three Carbon AtomsThe 1-alkynyl-2-methyl-1,2-epoxy-alkene 2 and -cycloalkenes 9, 28 and 29 were obtained by epoxidation of the conjugated en-ynes 1, 7, 26 and 27. The 12-membered ring en-ynes 26 and 27 were synthesized by ethynylation or propynylation of 2-methylcyclododecanone (19) to the 1-ethynyl- or 1-(1′-propynyl)-cyclododecanols 20 A/B and 21 A/B, respectively, followed by dehydration to give separable mixtures of the regio- and stereoisomeric en-ynes 22, 24, 26 and 23, 25, 27, respectively.Gas-phase thermolyses of the epoxides 2, 9, 28 and 29 were carried out under reduced pressure through a quartz tube at 550-600°. The formation of 5-hexine-2-one (3) and 4,5-hexadien-2-one (4) from 2 can be explained by [1, 5]- and [1, 3]- hydrogen shifts, respectively, and subsequent Claisen-type rearrangements. Thermolysis of the six-membered carbocyclic epoxide 9 induced the expected ring expansion by three carbon atoms to give 14% 4-cyclononynone (12), along with the ketones 13, 14 and 15 as by-products, which probably arose from surface induced heterolytic C, O-bond fission and Wagner-Meerwein-type rearrangement processes.Preliminary experiments with the thermolysis of the 12-membered carbocyclic ethynyl-epoxide 28, yielded a mixture, which contained 4-cyclopentadecynone (30) and afforded, after hydrogenation, cyclopentadecanone (31, exaltone®) in 36% yield as the semicarbazone. Traces of 3-methylcyclopentadecanone (32, rac, -muscone) were identified after thermolysis and hydrogenation of the propynyl-epoxide 29.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19770600857
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