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The reactions of 1,1-diaryl-2-(diphenylvinylidene)cyclopropanes and 1,1-diaryl-2-(2-phenylpropenylidine) cyclopropanes with aromatic amines in the presence of BF3·Et2O leads to the formation of pyrrolidine derivatives.

Substituted methyl 2,3,7-triazabicyclo[3.3.0]oct-3-ene-4-carboxylates and 1,2,7-triazaspiro[4.4]non-2-ene-3-carboxylates react with N-iodosuccinimide (or the system iodine-silver trifluoroacetate) to give, respectively, methyl 6-iodo-3-azabicyclo[3.1.0]hexane-6-carboxylates or methyl 1-iodo-4,6-dioxo-5-azaspiro[2.4]heptane-1-carboxylates as mixtures of exo and endo isomers.

Substituted 6,8-dioxo-2,3,7-triazabicyclo[3.3.0]oct-3-ene-4-carboxylates react with N-fluoropyridinium tetrafluoroborate to give mixtures of exo and endo isomers of 6-fluoro-2,4-dioxo-3-azabicyclo[3.1.0]hexane-6-carboxylates. Analogous reaction of 6,8-dioxo-1,2,7-triazaspiro[4.4]non-2-ene-3-carboxylates results in formation of syn,anti-isomeric 1-fluoro-4,6-dioxo-5-azaspiro[2.4]heptane-1-carboxylates.

Esters of 4-R-4,5-dihydro-1H-pyrazole-3,5,5-tricarboxylic acids with chlorine yield esters of 4-R-5-chloro-4,5-dihydro-3H-pyrazole-3,3,5-tricarboxylic acids that at thermolysis provide the esters of the corresponding 2-chlorocyclopropanetricarboxylic acid. The same esters react with bromine in dichloromethane at room temperature to give a mixture of esters of the corresponding 1H-pyrazole-3,5-dicarboxylic acids and 5-bromo-4,5-dihydro-3,3,5-tricarboxylic acids. From 5,5-diethyl 3-methyl 4,5-dihydro-1Hpyrazole-3,5,5-tricarboxylate and N-iodosuccinimide or a system iodine-silver trifluoroacetate we obtained 1,1-diethyl 2-methyl 2-iodocyclopropane-1,1,2-tricarboxylate.