PALLADIUM-ASSISTED FORMATION OF CARBON-CARBON BONDS. III: STUDY OF REACTIONS OF BISETA 2-(2,3,4-TRIMETHOXY-6-ACETYLPHENYL-C,O)BIS(MU -CHLORO)DIPALLADI UM(II) WITH SYMMETRICAL AND UNSYMMETRICAL INTERNAL ALKYNES. A STOICHIOMETRI C ROUTE TO HIGLY FUNCTIONALIZED SPIROCYCLIC AND BENZOFULVENE COMPOUNDS. I