CARBON-CARBON AND CARBON-NITROGEN BOND FORMATION MEDIATED BY RUTHENIUM(II) COMPLEXES - SYNTHESIS OF (1H)-ISOQUINOLINIUM DERIVATIVES

New cycloruthenated complexes can be obtained by transmetalation of [(eta6-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 [eta6-C6H6)RuCl2]2 affords the same cycloruthenated complexes though in lower yield. The resulting complexes are of the type (eta6-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 [(eta6-arene)Ru(eta4-C6H4CH(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=R2-1,2]+[PF6]- (R1 = R2 = Et, Ph; R1 = CO2Et, R2 = Ph) under mild conditions and in reasonable yields.