1314031-25-8Relevant articles and documents
Alternative reaction pathways in domino reactions of hydrazinediidozirconium complexes with alkynes
Gehrmann, Thorsten,Scholl, Solveig A.,Fillol, Julio Lloret,Wadepohl, Hubert,Gade, Lutz H.
supporting information; experimental part, p. 3925 - 3941 (2012/05/20)
Reaction of [Zr{(NAr)2Npy}(NMe2) 2] (Ar=3,5-xylyl: 2 a, mesityl: 2 b) with one or two molar equivalents of 1,1-diphenylhydrazine gave the mixed amido/hydrazido(1-) complex [Zr{(NMes)2Npy}(HNNPh2)(NMe2)] (3), the bis-hydrazido complex [Zr{(NMes)2Npy}(HNNPh 2)2] (4), and, in the presence of excess 4-dimethylaminopyridine (DMAP), hexacoordinate hydrazinediidozirconium complexes [Zr{(NXyl)2Npy}(=NN(Me)Ph)(dmap)2] (5) and [Zr{(NXyl)2Npy}(=NNPh2)(dmap)2] (6). The reaction of one equivalent of the zirconium-hydrazinediide [Zr{(NTBS) 2Npy}(NNPh2)(py)] (1) with disubstituted alkynes at RT for 16 h led to the formation of seven-membered diazazirconacycles 7 a-7 e in high yields. Similar reactivity was observed by reacting bis-amido complex 2 b with one molar equivalent of the corresponding alkyne and diphenylhydrazine. The formation of the seven-membered zirconacycles implied a key coupling step that involved the alkyne and one of the aryl rings of the diphenylhydrazinediido ligand. In some cases, such as the reaction with 2-butyne, the corresponding metallacycle was only obtained in modest yields (45 % for the reaction with 2-butyne) and a second major product, vinylimido complex 9, was formed in almost equal amounts (42 %) by 1,2-amination (formal insertion of the alkyne). The formation of compounds 7 a and 9 followed in part the same sequence of reaction steps and a key intermediate, an azirinido complex, represented a "bifurcation point" in the reaction network. Reaction of 1.2 equivalents of several diarylhydrazines and various substituted alkynes (1 equiv) at ambient temperature (or at 80 °C) in the presence of 10 mol % [Zr{(NXyl)2Npy}(NMe2)2] (2 a) gave the corresponding indole derivatives. On the other hand, the replacement of 1,1-diarylhydrazines by 1-methyl-1-phenyl hydrazine led to head-to-head cis-1,3-enynes in good yields. A fork in the road: Azirinidozirconium species A is the key intermediate for two reaction pathways in the metal-catalyzed coupling of diarylhydrazines and alkynes. Electrophilic metal-azirinide attack at the ortho C atom (C) affords substituted indoles. Copyright
Zirconium-catalyzed multistep reaction of hydrazines with alkynes: A non-fischer-type pathway to indoles
Gehrmann, Thorsten,Lloret Fillol, Julio,Scholl, Solveig A.,Wadepohl, Hubert,Gade, Lutz H.
supporting information; experimental part, p. 5757 - 5761 (2011/08/05)
Dominos at zirconium: A cascade of N-N and C-H scissions and C-C and C-N coupling steps in the coordination sphere of zirconium directly converts alkynes and hydrazines into indoles. The reaction pathway differs fundamentally from that of the Fischer indo
