| Popis: |
Fluorochlorocarbene, produced via the action of potassium-t-butoxide on sym -tetrachlorodifluoroacetone, has been added to tetramethylethylene, trimethylethylene, iso -butene, cis -butene, and trans -butene. 1-chloro-1-fluorocyclopropanes were formed in fair yields. Rates of carbene addition to the olefins, relative to iso-butene, were 31, 6·5, 1·0, 0·14 and 0·097, respectively. Structures were assigned to the isomeric cyclopropanes (formed from trimethylethylene and cis -butene) by F 19 NMR. In both cases, fluorochlorocarbene added so as to produce an excess of that isomer in which chlorine was syn to the largest number of Me groups. Isomer ratios were 2·35 (trimethylethylene) and 3·08 ( cis -butene). Additions to cis and trans -butene were greater than 99% stereospecific. |
