A novel route to the fluorinated diimines: carbon monoxide-promoted reductive homocoupling of fluorinated imidoyl iodides in the presence of a palladium catalyst

Abstract

A new catalytic access to the fluorinated diimines which involves palladium(0)-catalyzed reductive dimerization of the imidoyl iodides is presented.

Synthesis of 3,3,4,4-tetrafluoro-1,2-bis(imino)cyclobutanes: A cyclic version of fluorinated α-diimines

“…2. The planarity of the N C-C N moiety in cyclic diimine 14 is confirmed by X-ray analysis, whereas acyclic fluorinated diimines 1h and 1n possess twisted N C-C N structures due to the bulky trifluoromethyl groups [7,8]. And E,Z-geometry of both imino groups in crystalline 14 is revealed; one of the two pmethoxyphenyl (PMP) groups on nitrogen of the imine moiety is bound in anti geometry and another PMP group is bound in syn geometry.…”

“…Other routes to non-fluorinated cyclic diimines are transition metal-mediated coupling reactions of isocyanides with alkynes [11]. Selective chemical transformation of linear fluorinated a-diimines 1, which are readily prepared by Pd (0) catalyzed homocoupling reaction of the corresponding imidoyl iodides [7], is considered to be a quite effective methodology to synthesize cyclic fluorinated a-diimines.…”

“…In 2003, we presented the catalytic access to fluorinated diimines 1 involving palladium(0)-catalyzed reductive homocoupling of imidoyl iodides 3 [7]. The use of a catalytic amount of a Pd(0) complex in the presence of carbon monoxide (1 atm) allowed the selective formation of the fluorinated a-diimines 1 (Scheme 3).…”

A rich chemistry of fluorinated imidoyl halides

“…Heck type reaction of iodide 1 (X: I) with alkenes and Sonogashira type reaction with alkynes are useful for the preparations of imino-ene 40 and imino-yne 41 products [17], respectively. Homocoupling of imidoyl iodides to bistrifluoromethyl diimines 43 is also catalyzed by palladium in the presence of carbon monooxide which is essential presumably due to its reducing ability to regenerate active zero valent palladium under the reaction conditions [18] (Scheme 8).…”

An Economical, Green Pathway to Biaryls: Palladium Nanoparticles Catalyzed Ullmann Reaction in Ionic Liquid/ Supercritical Carbon Dioxide System

“…[14c-f] In these processes, reducing agents such as aldehyde, [14e] hydrogen gas, [17] formate salts, [18] alcohol, [19] glucose, [20] carbon monoxide, [21] ascorbic acid, [22] amine, [23] zinc [14f] and indium or germanium [10a] etc. were required for closing the reductive coupling cycle.…”