White solid catalyst, indicators

Experimental. Characterizations of a heterogeneous surface by means of surface group titration utilizing visible and ultraviolet chemical indicators to define the titration end point have frequently been employed with white solid catalysts(7-12), (17-20). Aspects of the surface acid group distribution have often correlated with the catalytic activity of the solid(2-9), (21-25). An adaptation of the technique appears to be suitable for studying the interactions between the surface acid groups in mixtures of carbon black and white reference solids. 

A suspension of Lindlar s catalyst [Pd (5% on CaCOs), 213 mg, 0.10 mmol], quinolone (0.81 mL, 6.8 mmol), and the alkyne (587 mg, 2.19 mmol) in EtOAc (22 mL) was stirred for 30 min. The flask was charged with hydrogen (1 atm), and the reaction mixture was stirred until NMR analysis indicated complete conversion (14 h). The reaction mixture was filtered through Celite and concentrated in vacuo. The crude product was purified by flash chromatography on silica gel (elution with EtOAc/CILCIi, 1 5 then EtOAc) to give 487 mg (83%) of the cz.v-olefin as a white solid. 

Analysis of the white solid showed a high chlorine content, presumably derived from the catalyst, cuprous chloride, used to form the trimer. Preliminary analytical studies indicated the starting reactant was similar in structure to isoprene, the starting material for synthetic rubber. Because of the structural similarity, the starting material, now known to be 2-chloro-1,3-butadiene, was dubbed chloroprene. In fact, it was derived from the dimer and was found to be readily synthesized from the reaction of the dimer and hydrogen chloride. 

To a flame-dried two-necked flask equipped with reflux condenser preheated to 100 °C was added 5 mL of a 0.095 M CH3NO2 solution of Meldrum s acid derivative 23 (0.475 mmol) under a dry N2 atmosphere. The solution was heated 5 min after which, 10 mol% (0.0475 mmol) of the catalysts (9 pL Bp3 OEt2, 5 pL TfOH or 25 mg Sc(OTf)2) wer e quickly added. The solution was heated to reflux for 20 min. The mixture was cooled to rrom temperature and concentrated, and the residue was purified by silica gel flash chromatography, eluting with 2 1 ethyl acetate/hexane to afford 24 as a white solid (m.p. 131-132 °C) in the yields indicated in the table. 

Aluminum alkyls are colorless liquids or solids. They are pyrophoric and may ignite spontaneously in air. They are often in solution with hydrocarbon solvents. Aluminum alkyls are pyrophoric materials in a flammable solvent. The vapors are heavier than air, water-reactive, and corrosive. Decomposition begins at 350°F. The four-digit UN identification number is 3051. The NFPA 704 designation is health 3, flammability 4, and reactivity 3. The white space at the bottom of the diamond has a W with a slash through it, indicating water reactivity. They are used as catalysts in polymerization reactions. 

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