A Catecholaldimine-Based Ni^II-Complex as an Effective Catalyst for the Direct Conversion of Alcohols to trans-Cinnamonitriles and Aldehydes

Abstract

A nickel(II) complex [Ni(HL)2] 1 was synthesized by treatment of a new catecholaldimine-based ligand with NiCl2·6H2O in methanol at room temperature. Complex 1 showed excellent catalytic activity where aromatic and heterocyclic alcohols were rapidly converted into trans-cinnamonitrile in a one-pot manner via oxidative olefination in the presence of KOH. The potential of the disclosed catalyst and the results obtained for the direct conversion of alcohols to two different functionalities (trans-cinnamonitrile and aldehydes) are well supported by DFT studies.

Iron(II) Phthalocyanine-Catalyzed Olefination of Aldehydes with Diazoacetonitrile: A Novel Approach to Construct Alkenyl Nitriles

“…The traditional and effective method is Knoevenagel condensation, while some side-reactions, including aldol, Cannizzaro, and self-condensation of nitriles, are accompanied. Recently, a variety of metal-catalyzed methods have been developed to prepare alkenyl nitriles, and they involve the dehydrogenative coupling of alcohols with nitriles catalyzed by Ru, Rh, Co, or Mn (Scheme a), vinylic C–H or C–X bond cyanation of alkenes or alkenyl halides with nitriles catalyzed by Pd or Cu (Scheme b), oxidative cyanation of alkynes or gem -difluoroalkenes with nitriles or azidotrimethylsilane (TMSN 3 ) catalyzed by Pd, Ni, or Cu (Scheme c), aryl-, bromo-, silyl-, or hydrocyanation of alkynes with K 4 Fe­(CN) 6 , BrCN, or aryl/alkyl nitriles catalyzed by Rh, Pd, Ni, or GaCl 3 (Scheme d), and formal group-exchange reaction between α,β -unsaturated ketone and nitriles catalyzed by Pd (Scheme e), as well as aza-Meyer-Schuster rearrangement of propargylic alcohols with para -tolylsulfonohydrazide catalyzed by FeCl 3 (Scheme f) . Undoubtedly, these methods provide alternative and very useful strategies for alkenyl nitriles, while most of them need expensive transition-metal catalysts, higher temperature, long reaction time, or even a highly toxic reagent; thus, it is necessary to develop new synthetic strategies to meet these challenges.…”