Cyclopalladated Complexes Derived from Phenylacetone Oxime. Insertion Reactions of Carbon Monoxide, Isocyanides, and Alkynes. Novel Amidines of the Isoquinoline Series

Abstract

Neutral and cationic six-membered C,N-palladacycles with the core "Pd{C,N-C 6 H 4 {CH 2 C(Me)NOH}-2}" have been obtained by oxidative addition of the oxime BrC 6 H 4 {CH 2 C(Me)NOH}-2 to "Pd(dba) 2 " (dba = dibenzylideneacetone) in the presence of mono-or bidentate ligands. The oximato complex [Pd{μ-C,N,O-C 6 H 4 {CH 2 C-(Me)NO}-2}(PTol 3 )] 2 forms after dehydrobromination of the appropriate oxime complex with K t BuO, while the pincer derivative [Pd{C,N,N′-C 6 H 4 {CH 2 C(Me)NOCH 2 py}-2}Br] results by attack of an in situ generated oximato complex to BrCH 2 py•HBr. Insertion of CO or RNC in some of the palladacycles causes a depalladation/coupling process, giving 1,2-dihydro-1-oxo-2-hydroxy-3-methylisoquinoline or 1,2dihydro-1-imino(R)-2-hydroxy-3-methylisoquinoline, respectively, while the insertion of alkynes produces eight-membered alkenyl(oxime) palladacycles "Pd{C,N-C(R′)C(R)C 6 H 4 {CH 2 C(Me)NOH}-2}". When using diphenylacetylene, a dimeric tetranuclear complex [{Pd(tbbpy)} 2 {μ-N,O-{η 3 -C 6 H 4 (C 4 Ph 4 ){CH 2 C(Me)NO}}}] 2 4+ forms instead, in which a π-allylcoordinated oximato, bearing a spirocyclic substituent, acts as the bridging ligand. The crystal structures of the oxime and of each type of complexes have been determined.

Bond Forming Reactions Involving Isocyanides at Diiron Complexes

“…Similarly to CO, isocyanides can be incorporated into catalytic mechanisms based on oxidative addition, isocyanide insertion, and reductive elimination. This emerging strategy, based on CNR insertion into M-element bonds, offers tremendous opportunities for the synthesis of fine chemicals containing a nitrogen functionality, and is largely dominated by Pd-catalyzed or Pd-promoted reactions [17][18][19][20][21][22]. Considerable efforts have been made in order to expand the research field to other transition-metals, given the strong interest in replacing noble and rare metals with more abundant and sustainable transition metals, such as iron.…”

Isocyanide-based multicomponent reactions in the synthesis of heterocycles

“…IMCRs can be achieved using catalysts or under catalystfree conditions 49 . Isocyanides have also been applied for synthesis of organic compounds via reaction with ortho-palladated complexes [93][94][95][96][97] .…”

Stereocontrol in Preparation of Cyclopalladated Alkylaromatic Oximes and Evaluation of Their Stereoselective Esterase-Type Catalytic Activity

“…In crystal, two independent molecules are distinguished by two different rotation angles of a pyridine ring. Also, short distances H­(1O)...Cl(1) and H­(1OA)...Cl­(1A) (∼2.23 Å) prove the existence of intramolecular hydrogen bond H···Cl, which is typical for such oxime systems. ,, The H-bond sustains in solution, which is clearly seen by shifting of OH chemical shift from 8.2 to 10.2 ppm in 1 H NMR spectrum in chloroform- d .…”

“…Thus, the oximate anion acting together with hydroxide as a nucleophile enhances the rate of hydrolysis of the substrate significantly . While cyclopalladation of oximes was performed for the first time more than 40 years ago, , these complexes are still popular precursors for synthesis of more complicated palladium complexes. − Although their catalytic properties were already explored in the hydrolysis processes, no information is found on the application of chiral oximes in such reactions.…”