Cyclopropanes 1,1-dihalogeno-

Ciamician-Dennstedt rearrangement. Expansion of the pyrrole ring by heating with chloroform or other halogeno compounds in the alkaline solution. The intermediate dichlorocarbene, by addition to the pyrrole, forms an unstable dihalogeno-cyclopropane that rearranges to a 3-halogenopyri-dine. 

A mass spectral study of the 1,1-dihalogeno precursors of (10) and (11) and suitable deuteriated analogues has shown that complete hydrogen scrambling occurs prior to the loss of H or X from the molecular ion. A series of cyclopropyl ethers has been subjected to chemical ionization mass spectrometry and other routine electron-impact studies of cyclopropane-containing compounds are included for completeness. The gas-phase ion chemistry of monosubstituted cyclopropanes has been examined and ion-impact energy-loss spectrometry applied to a series of cycloalkenes including cyclopropene. ... 

A new synthetic route to cyclopropane derivatives from olefins, which should have wide application, involves the reaction between olefins and giem-dihalogeno-compounds... 

From norbornene, bicyclo[3,2,l]oct-2-ene derivatives, and 1-methyl-1,2-dihydroquinoline, PTC proved an efficacious method of dihalogeno-cyclopropanation after other methods had failed or had given very poor yields. With ap-unsaturated esters and nitriles which bear an a-substituent, the PTC method gives cycloaddition. (From methyl acrylate, acrylonitrile, or vinyl acetate there is only nucleophilic addition across the double bond.) From buta-1,3-diene and dichlorocarbene generated by PTC, an improved yield of... 

The effect of a halide upon the cyclopropanation of cyclohexene by diethyl-zinc-di-iodomethane has been reported. Although good yields of norcarane are obtained in the absence of lithium or magnesium halides, in their presence the yield of norcarane deteriorates and there is an increase in the yield of propyl and butyl iodides. Other dihalogeno-compounds besides di-iodo-methane may be used with diethylzinc and, in the case of chloroiodomethane. 

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