54325-12-1

Insoluble precious metal chlorides in polymeric form (i.e., PtCl2, PdCl2, AuCl, RhCl3) are commonly used as catalysts for a plethora of organic reactions in solution. Here we show that only the minor soluble fraction of these precious metal chlorides (typically 5-30%) is catalytically active for the hydroamination, hydroalkoxylation, hydrosilylation, and cycloisomerization of alkynes and alkenes, and that the resting insoluble metal is catalytically useless. To circumvent this waste of precious metal and follow a rational design, we generate here well-dispersed Pt(II) and Pd(II) single sites on zeolite Y, with an exquisite control of the Lewis acidity, to catalyze different hydroaddition reactions to alkynes and alkenes with up to 104 catalytic cycles (at least 2 orders of magnitude superior to precious metal chlorides) and with high isolated yields (82-99%, >15 examples).

Three natural aromadendrane sesquiterpenes, (-)-epiglobulol, (-)-4β,7α-aromadendranediol, and (-)-4α,7α- aromadendranediol, have been synthesized in only seven steps in 12, 15, and 17% overall yields, respectively, from (E,E)-farnesol by a stereodivergent gold(I)-catalyzed cascade reaction which forms the tricyclic aromadendrane core in a single step. These are the shortest total syntheses of these natural compounds.

The effect of doping Lindlar catalyst with different metal salts (shown in Table 1) on selectivity, during semihydrogenation of some acetylenes to the corresponding olefins, has been studied.Lindlar catalyst modified with MnCl2 has been found to be more selective and reproducible.