Trifluoromethyl-substituted cyclopropene

A small number of trifluoromethyl-substituted cyclopropenes has been made. Laganis... 

The AMI estimated activation barrier for nitrogen elimination was 17.5 kcal/mol. This means that isolation of the cycloadduct between cyclopropene and 2,5-bis(trifluoromethyl)-l,3,4-oxadiazole might be very hard. If we explore other cycloadducts between cyclopropene and 2 and 5 disubstituted 1,3,4-oxadiazoles and their activation barriers for nitrogen elimination, we can see that transition state structures are very similar with differences in C-N distance for the carbomethoxy substituent of 0.536 A, and the methyl substituent of 0.605 A instead of trifluoromethyl substitution. These results proved that all the transition state structures were very similar. That was also true for computed activation barriers. With carbomethoxy as a substituent, the activation barrier was 14.7 kcal/mol and with methyl as substituent, 16.7 kcal/mol. All of these values suggested that isolation of the cycloadduct might not be possible and that a substituted pyran should be expected as the final cycloaddition product. 

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