PALLADIUM-ASSISTED FORMATION OF CARBON-CARBON BONDS .6. STUDY OF THE REACTIVITY OF (O-FORMYLARYL)-PALLADIUM OR (O-ACETYLARYL)PALLADIUM COMPLEXES WITH ALKYNES - SYNTHESIS OF INDENONES AND INDENOLS

The reaction of (PhCH(2)PPh(3))(2)[Pd(R(1))Cl(mu-Cl)](2) (1; R(1) = 6- formyl-2,3,4-trimethoxyphenyl) with PhC=CPh gives a 6.5:1 mixture of 4 ,5,6-trimethoxy-2,3-diphenylinedenone (2)and 4,5,6-trimethoxy-2,3-diph enyl-1H-indenol(3). When the same reaction is carried out with MeO(2)- CC=CCO(2)Me or with Me(3)SiC=CSiMe(3), the compounds 4,5,6-trimethoxy- 2,3-bis(methoxycarbonyl)indenone (4) and R(1)C=CSiMe(3) (5) are obtain ed, respectively. The reactions of PhC=CPh with [Pd(R(1))Cl(bpy)] (6; bpy = 2,2'-bipyridine), in the presence of AgClO4, or with [Pd(R(1))(M eCN)(bpy)]ClO4 (7) yield 3 and [Pd(mu-OH)(bpy)](2)(ClO4)(2) (8a). If 7 reacts with PhC=CPh under anhydrous conditions, the indenone 2 is obt ained. The complex [Pd(R(2))(MeCN)(bpy)]ClO4 (9; R(2) = 2-formyl-3,4,5 -trimethoxyphenyl) reacts with PhC=CPh, giving 5,6,7-trimethoxy-2,3-di phenyl-1H-indenol (10) or, under anhydrous conditions, 5,6,7-trimethox y-2,3-diphenylindenone (11). A 1:1 mixture of both compounds is obtain ed by reacting [Pd(eta(2)-R(2))(mu-Cl)](2) (12) With PhC=CPh. [Pd(eta( 2)-R(3))(bpy)](CF3SO3) (13; R(3) = 6-acetyl-2,3,4-trimethoxyphenyl) re acts with the alkynes RC=CR' (R = R' = Ph, 4-tolyl, CO(2)Me, Me, Et; R = Ph, R' = CO(2)Et, 4-nitrophenyl, 4-methoxyphenyl, Me; R = (t)Bu, R' = H, Me), yielding [Pd(mu-OH)(bpy)(2)(CF3SO3)(2) (8b) and 1-methylind enols 14-24. The catalytic reaction of[Hg(R(1))(2)] with PhC=CPh and C uCl2 in the presence of Q(2)[Pd2Cl6] (1:6:2:0.05; Q = Me(4)N, PhCH(2)- PPh(3)) gives the indenol 3 in 62% yield with respect to the group R p resent in the mercurial compound. When a similar reaction (Q = PhCH(2) PPh(3)) is carried out under nitrogen, the spirocyclic compound thoxy- 1,2,3,4-tetraphenylspiro[4.5]1,3,6,9-decatet raen-8-one (26) is obtain ed.