[3+2] Cycloaddition of ruthenium azido complex with Ethyl propiolate and related reactions

Abstract The [3+2] cycloaddition reaction of ethyl propiolate with ruthenium azido complex [Ru]−N 3 ( 1 , [Ru] = ( η 5 -C 5 H 5 )(dppe)Ru, dppe = Ph 2 PCH 2 CH 2 PPh 2 ) has been investigated. The metal-bound heterocyclic complex produced is N (2)-bound triazolate [Ru]N 3 CHCO 2 Et ( 2 ). A regiospecific alkylation happens by treatment of 2 with organic halides and gives a series of cationic N (1)-bound N (3)-alkylated-4-ethoxycarbonyl triazolato complexes {[Ru]N 3 (R)C 2 HCO 2 Et}[X] ( 3a , R = CH 3 , X = I; 3b , R = CH 2 Ph, X = Br ; 3c , R = CH 2 C 6 F 5 , X = Br; 3d , R = CH 2 CN, X = I; 3e , CH 2 CO 2 CH 3 , X = Br) and the following cleavage of the Ru-N bond of 3a and 3b gives ruthenium halides and N (1)-alkylated five-membered-ring organic triazoles N 3 (R)C 2 HCO 2 Et ( 4a , R = CH 3 ; 4b , R = CH 2 Ph). The structures of 2 and 3c have been determined by single-crystal X-ray diffraction analysis.