Palladium-Assisted Formation of Carbon−Carbon Bonds. 4.¹ 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 = C 6 H(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 [PdCl 4 ] 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 NaClO 4 to give [Pd(Ar)(bpy)(PPh 3 )]ClO 4 ( 6 ). Treatment of 5 with AgClO 4 and py affords [Pd(Ar)(py) 3 ]ClO 4 ( 7 ), which reacts with PPh 3 to give cis- [Pd(Ar)(py) 2 (PPh 3 )]ClO 4 ( 8 ). A comparative study of the reactions of 3 - 5 with various alkynes has been carried out. Thus, 3 reacts with Tl(CF 3 SO 3 ) and EtC⋮CEt or with AgClO 4 and PhC⋮CPh to give the (π-allyl)palladium complex (η 3 -10-(ethoxymethyl)-6,7,8-trimethoxy-1,2,3,4-tetraethylspiro[4.5]-1,3,6-decatrien-8-enyl)(bpy)palladium(II) trifluoromethanosulfonate ( 9 ) or the monoinserted complex [Pd{ cis -C(Ph) C(Ph){C 6 H(CH 2 OEt)-6-(OMe) 3 -2,3,4}}(bpy)]ClO 4 ( 10 ), respectively. Complex 10 reacts with PPh 3 giving [Pd{ cis- CPh CPh(Ar)}(PPh 3 )(bpy)]ClO 4 ( 14 ). Complex 4 reacts with Tl(CF 3 SO 3 ) 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){C 6 H(CH 2 OEt)-6-(OMe) 3 -2,3,4}}(tmeda)]CF 3 SO 3 ( 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(CF 3 SO 3 ) or AgClO 4, 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(CO 2 Me)(Ar)}{OS(O) 2 CF 3 }(py) 2 ] ( 13 ). The structures of compounds 6, 11, 12c, and 13 have been determined by X-ray diffraction.