Carbon-carbon and carbon-nitrogen bond formation mediated by ruthenium(II) complexes: Synthesis of (1H)-isoquinolinium derivatives

Article abstract of DOI:10.1021/om00035a034

New cycloruthenated complexes can be obtained by transmetalation of [(η⁶-arene)RuCl₂]₂ (arene = C₆H₆ or i-PrC₆H₄Me-1,4) with several mercury- or zinc-metalated [(N,N-dimethylamino)-methyl]benzene derivatives. Intramolecular C-H activation using these amines with [(η⁶-C₆H₆)RuCl₂]₂ affords the same cycloruthenated complexes though in lower yield. The resulting complexes are of the type (η⁶-arene)RuCl(C,N) [(C,N) = C₆H₄CH₂NMe₂-2, (R)-(+)-C₆H₄CH-(Me)NMe₂-2, C₆H₂(OCH₂O-2,3)CH₂NMe₂-6] and have a rigid structure containing a five-membered Ru-C-C-C-N chelate ring, both in the solid state and in solution. Reaction of the cycloruthenated complexes with internal alkynes can lead to the formation of novel Ru(0) sandwich complexes of the type [(η⁶-arene)Ru(η⁴-C₆H ₄CH(R)NMe₂CR¹=CR₂-1,2)] ⁺[PF₆]^- (R = H, Me; R¹, R² = alkyl, aryl, or carboxyalkyl). The formation of the heterocyclic units occurs with good chemo- and regioselectivities, asymmetric alkynes being incorporated in such a way that the acetylene carbon with the sterically least demanding substituent becomes attached to the nitrogen atom of the arylamine. Oxidative demetalation induced by CuBr₂ allows the isolation of the free organic (1H)-isoquinolium derivatives [C₆H₄CH₂NMe₂CR¹=CR ²-1,2]⁺[PF₆]^- (R¹ = R² = Et, Ph; R¹ = CO₂Et, R² = Ph) under mild conditions and in reasonable yields.