Nucleophilic Halogenations of Diazo Compounds, a Complementary Principle for the Synthesis of Halodiazo Compounds: Experimental and Theoretical Studies

Three
new protocols for the nucleophilic halogenations of diazoesters,
diazophosphonates, and diazopiperidinylamides as complementary methods
to our previously reported electrophilic halogenations are presented
for the first time. On the basis of hypervalent α-aryliodonio
diazo triflate salts 1A, 2A, and 3A, the corresponding halodiazo compounds are generated via nucleophilic
halogenations with tetrabutylammonium halides or potassium halides.
The products from subsequent catalytic intermolecular cyclopropanations
of the halodiazoesters and halodiazophosphonates and thermal intramolecular
C–H insertion of the brominated diazopiperidinylamide are obtained
in moderate to good yields after two steps. DFT calculations are presented
for the diazoesters to give insight into the mechanism and transition
states of the nucleophilic substitutions with the neutral nucleophiles
dimethyl sulfide and triethylamine and the bromination with Br–.