Copper-Catalyzed Transformation of Hydrazones into Halogenated Azabutadienes, Versatile Building Blocks for Organic Synthesis

Abstract

A one-step copper-catalyzed reaction of aldehyde-derived N-substituted hydrazones with CCl4 resulted in efficient synthesis of 4,4-dichloro-1,2-diazabuta-1,3-dienes. It was proven that this C–C bond-forming cascade reaction operates via an addition of trichloromethyl radical to the CN bond of hydrazone followed by a base-induced elimination of HCl. The reaction was found to be very general, as diverse hydrazones possessing various aromatic groups at N-site, as well as aromatic, aliphatic, and heterocyclic substituents at C-site, are capable partners for coupling with a wide range of polyhalogenated compounds (CCl3Br, CBr4, CCl3CN, CCl3COOEt, CCl3CF3, CBr3CF3) to produce a family of functionalized 1,2-diazabuta-1,3-dienes. It was demonstrated that the prepared heterodienes are highly versatile building blocks for straightforward assembly of various valuable acyclic and heterocyclic molecules.

Dichloro‐Substituted 1,2‐Diazabuta‐1,3‐dienes as Highly Reactive Electrophiles in the Reaction with Amines and Diamines: Efficient Synthesis of α‐Hydrazo Amidinium Salts

“…13 C NMR (100.6 MHz, CDCl 3 ): δ = 23.4 [N(‐CH 2 ‐ CH 2 ‐) 2 ], 25.6 [=N + (‐CH 2 ‐ CH 2 ‐) 2 ], 50.8 [N(‐ CH 2 ‐CH 2 ‐) 2 ], 51.9 [=N + (‐ CH 2 ‐CH 2 ‐) 2 ], 114.2, 120.7, 123.1, 128.3, 128.6, 129.0, 132.1, 144.3, 156.6 ppm. All spectroscopic data are in agreement with literature data …”

“…All solvents were dried by standard procedures and freshly distilled before use. Dichloro‐substituted 1,2‐diazabuta‐1,3‐dienes were prepared as reported previously …”

“…It has been shown that various five‐, six‐, and seven‐membered heterocycles with one or two nitrogens in the structure can be efficiently prepared using these molecules as starting materials . Recently, we developed a new synthesis of 1,2‐diaza‐1,3‐dienes with two chlorine atoms on the C–C double bond . 1,2‐Diaza‐1,3‐dienes of this type are almost unknown in the literature, and information about the reactivity of such heterodienes is very rare .…”

Synthesis and Spectral Study of a New Family of 2,5-Diaryltriazoles Having Restricted Rotation of the 5-Aryl Substituent

“…Electronically and sterically different o-propargyloxybenzaldehydes can be used for this aim. Moreover, the corresponding naphthalene derivative was prepared as well (Schemes 2 and 3) [26]. In a similar manner, a set of dienes 2h-o having different aryl substituents at the nitrogen was prepared from the parent o-propargyloxy-benzaldehyde and substituted aryl hydrazines.…”

“…These compounds can be prepared using the reaction of carbon tetrachloride witH-N-substituted hydrazones of aldehydes in the presence of CuCl as a catalyst. [26,27] Recently we demonstrated that these compounds are also interesting diazodyes [28,29]. The reaction of 4,4-dichloro-1,2-diazabuta-1,3-dienes with sodium azide has been found to open straightforward access to extremely rare 1,1-bis-azides ( Figure 2).…”