Reaction with palladium compounds structure

The first example of an indolo[2,3-a]carbazole derivative reported with a reasonably estabhshed structure was the mono N-methylated system 9, prepared via dehydrogenation with palladium on charcoal of the octahydro derivative 10, available via reaction of the aminocarbazole 11 with 2-hydroxycyclohexanone in the presence of a trace amount of anihnium bromide (Scheme 1). An approach toward the parent compound 1 using the same method has also been attempted, although without success (56JCS4783). The utility of this route is impaired by the complexity of the starting material, which requires multistep preparation, and the harsh conditions of the final step. 

Several products other than 2,2 -biaryls have been isolated following reaction of pyridines with metal catalysts. From the reaction of a-picoline with nickel-alumina, Willink and Wibaut isolated three dimethylbipyridines in addition to the 6,6 -dimethyl-2,2 -bipyridine but their structures have not been elucidated. From the reaction of quinaldine with palladium-on-carbon, Rapoport and his co-workers " obtained a by-product which they regarded as l,2-di(2-quinolyl)-ethane. From the reactions of pyridines and quinolines with degassed Raney nickel several different types of by-product have been identified. The structures and modes of formation of these compounds are of interest as they lead to a better insight into the processes occurring when pyridines interact with metal catalysts. 

Hydrosilanes react with butadiene by the catalysis of palladium compounds, but the nature of the reaction is somewhat different from that of the telomerization of other nucleophiles described before. Different products are obtained depending on both the structure of silanes and the reaction conditions. Trimethylsilane and other trialkylsilanes reacted with butadiene to give the 1 2 adduct, l-trialkylsilyl-2,6-octadienes (65), in high yield (98%) (62-64). Unlike other telomers which have the 1,6-octadienyl chain, the telomers of silanes have the 2,6-octadienyl chain. As catalysts, Pd(PPh3)2 (maleic anhydride), PdCl2(PhCN)2, PdCl2, and 7r-allylpalladium chloride were used. Methyldiethoxysilane behaved similarly to give the 1 2 adduct. 

Over the years, however, information has emerged that indicates that the shape of Fig. 2 may he a simplification or may be restricted to special circumstances. Of great importance has been the structural elucidation of large numbers of 5-coordinate complexes. The isolation of these compounds means that any closely related species encountered on the reaction coordinate could reasonably be regarded as intermediates and not transition states. The geometry of these compounds is therefore of great interest, and a structural survey of these types is worthwhile. At this stage we widen the scope to cover all the d ion complexes in order to make comparisons and contrasts with the reactions of palladium(II) and platinum(II) on which we have concentrated thus far. 

Compound A has the formula CjoHi. On catalytic hydrogenation over palladium, it reacts with only 1 molar equivalent of Hg. Compound A also undergoes reaction with ozone, followed by zinc treatment, to yield a symmetrical diketone, B (CioHie02). (a) How many rings docs A have (b) What are the structures of A and B ... 

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