Control of the reactivity of cyclopalladated complexes for the synthesis of heterocyclic compounds

Iodide effects in transition metal catalyzed reactions

“…The proposed catalytic species is [Pd(CO) 2 I 2 ] 2− formed from the [Pd 2 I 6 ] 2− precursor. 102 The PdI 2 /KI system also catalyzes some C-C bond formation and cycloisomerization reactions not involving carbon monoxide. 103 Thus (Z)-3-methylpent-2-en-4-yn-1-ol gave 2,3dimethylfuran in 92% yield with PdI 2 /2KI in dimethylacetamide at 25 °C (Fig.…”

Molecular iodine catenation in the anionic chains [Pd2I6(I2)]2–

“…The I-I distance within the catenated iodine molecule as observed in these chains is remarkably short, d(I4-I4') = 276.5(2) pm, and is only slightly longer than in solid iodine at 110 K, 271.5(6) pm [31]. In the crystal structure, the anionic chains proceed parallel to the crystallographic c axis, well separated from each other by the bulky [(H 5 O 2 )(db24c8)] 2-anions which are stabilized by low charged bulky cations in the solid state [24][25][26][27][28][29][30], the linkage of these dinuclear anions through dihalogen molecules (Cl 2 , Br 2 , and I 2 ) to form chains or networks appears to be an extremely rare structural motif. …”

Synthesis of isoquinolines by electrophilic ring closure of iminoalkynes

“…~P h (3) In our own group, Roesch reported the formation of numerous 3,4disubstituted isoquinolines by the palladium-catalyzed annulation of internal alkynes (eq 4) 5 and also 3-substituted isoquinoline derivatives by a copper(l)catalyzed ring closure (eq 5 Roesch has also discovered one reaction which utilizes an external electrophile, iodine, to ring close an iminoalkyne to give the 3,4-disubstituted isoquinoline in a modest yield (eq 6). 8 3 equiv 12 3 equiv NaHCO 3…”

“…2 Also it has been shown by Larock and Roesch, that monosubstituted isoquinolines and pyridines can be synthesized by the palladiumcatalyzed coupling of terminal acetylenes onto the tert-butyl imine of oiodobenzaldehyde and 3-halo-2-alkenals, followed by subsequent coppercatalyzed cyclization. 3 The synthesis of disubstituted isoquinolines has led us to investigate another method for their synthesis. This approach involves the electrophilic ring closure of iminoalkynes by various external electrophiles.…”

“…Pfeffer has reported the synthesis of disubstituted isoquinolines by using N,N-dimethylbenzylamine palladium complexes (eq 2). 3 This synthesis is also disadvantageous due to the use of stoichiometric palladium salts.…”