Reduction of a 1‐Aza‐1,3‐diene to a 1‐Azabut‐2‐ene‐1,4‐diyl Dianion: An Unusual Reaction Course

Abstract

We have been searching for a rather simple method for the synthesis of 1-aza-1,3-diene complexes of early transition metals for quite some time. This search is motivated by some remarkable applications of these compounds: For example, (1-aza-1,3-diene)zirconocene complexes react diastereoselectively with carbonyl compounds to form seven-membered zirconacycles, [1a] from which highly substituted five-membered oxygen heterocycles, which are applied in the synthesis of natural products and active agents, can be separated.[1b]Titanium 1-aza-1,3-diene complexes in turn offer a simple approach to novel metallacyclic alkylidene complexes. For example, in attempts to methylate (1-aza-1,3-diene)titanium complexes even under mild conditions, an a-agostic Ti ! HÀC interaction on the terminal methine group of the 1-aza-1,3-diene ligand triggers an a-methane elimination that results in

Rearrangements and Stereomutations of Metallacycles Derived from Allenes and Imidozirconium Complexes

“…The MAD moiety is strongly bent with respect to the Zr−N−C plane, but Zr−C11 and Zr−C12 bond distances of 2.65 and 2.54 Å, respectively, reveal that 18 is best described as a metallacyclopentene, rather than as an η 4 -MAD complex. This observation has been made in other reports from the literature. − The strain of the bridgehead double bond is evident in the reduced torsion angle about that bond (157°). When crystals of 18a were redissolved in C 6 D 6 , the same 3:1 mixture of 18a and 18b was observed by 1 H NMR spectroscopy.…”

Reactions of Secondary Allylamines with Bis(η5:η1-pentafulvene)titanium Complexes: Selective Formation of Monoazabutadiene Titanium Complexes by N–H and C–H Bond Activation

“…Various coordination modes of monoazabutadiene ligands are known. − Group IV metallocene and non-metallocene type complexes are known to exhibit a characteristic envelope structure (Scheme ). ,− …”

Between Enamide and Azaallyl Structures: Novel Flexible N-Chelate Ligands in the Lanthanide Chemistry

“…Recently we reported on the reduction of the 1-aza-1,3-diene 1 to the 1-azabut-2-ene-1,4-diyl dianion 3 , whereinitially unexpected but nearly quantitativelythe dilithium hexa-1,5-diene-1,6-diamide 2 was generated as an intermediate during the course of the reaction (Scheme ) 1 Course of the Reaction of the 1-Aza-1,3-diene 1 with Lithium …”