PREPARATION OF A NEW CYCLOPROPARENE SYNTHON, 1-BROMO-2-CHLOROCYCLOPROPENE, AND STUDIES ON THE SYNTHESIS AND PROPERTIES OF BICYCLO(4.1.0)HEPT-1,6-ENE AND BICYCLO(4.1.0)HEPT-1,7-ENE
ARNEY, BENNY ERVIN, JR.
Doctor of Philosophy
1-Bromo-2-chlorocyclopropene (BCC) was prepared by treating 1-bromo-2,2-dichlorocyclopropyltrimethylsilane with tetrabutylam- monium fluoride in tetrahydrofuran at -20(DEGREES)C. Diels-Alder reactions of BCC with 1,3-dienes provide 1,6-dihalobicyclo 4.1.0 hept-3-enes which can be treated with potassium tert-butoxide in tetrahydro- furan to give the corresponding cycloproparenes. This approach was used successfully to prepare benzocyclopropene, 1H-cyclo- prop b anthracene, bis-cyclobutabenzocyclopropene, bis-cyclo- pentabenzocyclopropene, and 1H-2,3,4,5,6,7,8,9-octahydrocyclo- propa 1 phenanthrene. Tetrabutylammonium fluoride supported on glass helices was used to generate strained double bonds from (beta)-halosilanes in the gas phase. Bicyclo 4.1.0 hept-1,7-ene and bicyclo 4.1.0 hept-1,6- ene were prepared and their thermal chemistry investigated. Bicyclo 4.1.0 hept-1,7-ene undergoes Ene type reactions to give two dimeric cyclopropene products. One (25) is stable at room temperature and the other undergoes a second dimerization via a 2+2 cycloaddition to give a tetramer. Bicyclo 4.1.0 hept-1,6-ene also undergoes an Ene type reaction to give 25. Cyclopropene (25) was observed to undergo a thermal epimerization reaction at 25(DEGREES)C by way of a vinyl carbene intermediate. Reaction of 1-trimethylsilyl-2,2-dichlorobicyclo 4.1.0 heptane with the supported fluoride gave only 2-chloro-1,3-cycloheptadiene.