Palladium-assisted formation of carbon-carbon bonds .4. Synthesis and reactivity of a water-soluble (2,3,4-trimethoxy-6-(ethoxymethyl)phenyl)palladium(II) complex. Reactions with alkynes of its derivatives: Further insight into the pathway of formation of highly functionalized organic spirocycles and X-ray structures of model intermediates

Mercuration of 3,4,5-trimethoxybenzyl chloride with mercury(II) acetate in ethanol, and further addition of aqueous NaCl, affords the compound [Hg(Ar)Cl] (1) [Ar = C6H(CH(2)OEt)-6-(OMe)(3)-2,3,4], which reacts with (Me(4)N)Cl to give [Hg(Ar)(2)] (2). Complex 2 reacts with K-2[PdCl4] in water/acetone to give solutions from which, after addition of 2,2'-bipyridine (bpy), N,N,N ',N '-tetramethylethylenediamine (tmeda) or pyridine (py), complexes [Pd(Ar)Cl(bpy)] (3), [Pd(Ar)Cl(tmeda)] (4), or trans-[Pd(Ar)Cl(py)(2)] (5), respectively, can be isolated. Complex 3 reacts with PPh(3) and NaClO4 to give [Pd(Ar)(bpy)(PPh(3))]ClO4 (6). Treatment of 5 with AgClO4 and py affords [Pd(Ar)(py)(3)]ClO4 (7), which reacts with PPh(3) to give cis-[Pd(Ar)(py)(2)(PPh(3))]ClO4 (8). A comparative study of the reactions of 3-5 with various alkynes has been carried out. Thus, 3 reacts with Tl(CF3SO3) and EtC=CEt or with AgClO4 and PhC=CPh to give the (pi-allyl)palladium complex (eta(3)-10-(ethoxymethyl)-6,7,8-trimethoxy-1,2,3,4-tetraethylspiro[4.5]-1,3,6-decatrien-8-enyl)(bpy)palladium(II) trifluoromethano-sulfonate (9) or the monoinserted complex [Pd{cis-C(Ph)=C(Ph){C6H(CH(2)OEt)-6-(OMe)(3)-2,3,4}})(bpy)]ClO4 (10), respectively. Complex 10 reacts with PPh(3) giving [Pd{cis-CPh=CPh-(Ar)}(PPh(3))(bpy)]ClO4 (14). Complex 4 reacts with Tl(CF3SO3) and MeO(2)CC=CCO(2)Me or EtC=CEt yielding the vinyl-substituted complex [Pd{cis-C(CO(2)Me)=C(CO(2)Me){C6H(CH(2)OEt)-6-(OMe)(3)-2,3,4}}(tmeda)]CF3SO3 (11) or the spirocyclic compound 10-(ethoxymethyl)-6,7-dimethoxy-1,2,3,4-tetraethylspiro[4.5]-1,3,6,9-decatetraen-8-one (12a). When 5 reacts with EtC=CEt, PhC=CPh, or ToC=CTo (To = C(6)H(4)Me-4), in the presence of Tl(CF3SO3) or AgClO4, the corresponding spirocyclic compounds 12a, 12b (tetraphenyl), or 12c (tetratolyl), respectively, are obtained, whereas the reaction with MeO(2)CC=CCO(2)Me gives the diinserted complex trans-[Pd{cis,cis-C(CO(2)Me)=C(CO(2)Me)C(CO(2)Me)=C(CO2(Me)(Ar)}{OS(O)(2)CF3}(py)(2)] (13). The structures of compounds 6, 11, 12c, and 13 have been determined by X-ray diffraction.