Harun M. Mbuvi

O-H insertion and tandem N-H insertion/cyclization reactions using an iron porphyrin as catalyst with diazo compounds as carbene sources

Iron(III) tetraphenylporphyrin chloride, Fe(TPP)Cl, efficiently catalyzed the insertion of carbenes derived from methyl 2-phenyldiazoacetates into O-H bonds of aliphatic and aromatic alcohols, with yields generally above 80%. Although the analogous N-H insertions are rapid at room temperature, the O-H insertion reactions are slower and required heating in refluxing methylene chloride for about 8 hours using 1.0 mol.% catalyst. Fe(TPP)Cl was also found to be effective for tandem N-H insertion/cyclization reactions when 1,2-diamines and 1,2-alcoholamines were treated with diazo reagents to give piperazinones and morpholinones and related analogs such as quinoxalinones and benzoxazin-2-ones. This approach provides a new one-pot route for synthesizing these classes of heterocyclic compounds.

Addition of carbenes derived from aryldiazoacetates to arenes using chloro(tetraphenylporphyrinato)iron as catalyst

Chloro(tetraphenylporphyrinato)iron, Fe(TPP)Cl, is an active catalyst for the Buchner addition of para-substituted methyl 2-phenyldiazoacetates, 1a–d, to substituted benzenes. Yields greater than 70% have been achieved at temperatures ranging from 60–100°C. Reactions of substituted methyl 2-phenyldiazoacetates with benzene gave rapidly equilibrating mixtures of norcaradienecycloheptatriene valence isomers, 2a–d/2′a–d, in yields over 70%. Treatment of chlorobenzene with methyl 2-phenyldiazoacetate produced a regio-isomeric mixture of 7-carbomethoxy-2-chloro-7-phenylnorcaradiene/7-carbomethoxy-2-chloro-7-phenylcycloheptatriene, 3a/3′a, and 7-carbomethoxy-3-chloro-7-phenylnorcaradiene/7-carbomethoxy-3-chloro-7-phenylcycloheptatriene, 4a/4′a. When p-methylanisole was treated with methyl 2-phenyldiazoacetate at 80°C, a product that largely favored a fused cyclopropane structure, 7-carbomethoxy-2-methoxy-5-methyl-7-phenylnorcaradiene, 12a, was obtained along with the benzylic C–H insertion product methyl 3-(p-methoxyphenyl)-2-phenylpropionate, 13a. Heating the norcaradiene product 12a at 110°C yielded the ring-opened diarylacetate, 14a. The diene forms of the fluxional norcaradiene-cycloheptatriene systems were trapped with benzyne to give one stereoisomer of 3,3-disubstituted benzhomobarralenes, 18a–d. The norcaradiene-cycloheptatriene valence isomers were quantitatively converted into ring-opened diaryl acetate products upon acidification in acetonitrile. Rates for the addition of methyl (p-chlorophenyl)diazoacetate to benzene were first order with respect to the diazo reagent. A concerted mechanism involing an iron carbene complex is proposed for these iron porphyrin-catalyzed Buchner reactions.

Rice Husk Ash Derived Zeolite Blended with Water Hyacinth Ash for Enhanced Adsorption of Cadmium Ions

In order to help curtail or imposesustained control to the offensive water hyacinth plant, it is essential to explore ways of generating water remediation materials from it. In the current study, the capacity and efficacy of water hyacinth ash (WHA), its insoluble residue (WHAR) and rice husk ash (RHA) to remove cadmium ions and methylene blue from contaminated water was investigated. Mixtures of the two ashes were used to formulate zeolitic materials by hydrothermal reactions. Material A, ZMA was prepared by using rice husk ash and the soluble portion of WHA while for material B, ZMB a mixture of equal amounts the two ashes including the insoluble fraction of WHA were used. Batch experiments was carried out to determine the effect of metal ion concentration, initial PH, contact time (t), temperature (T), shaking speed and adsorbent dose on percentage removal of Cd 2+ and methylene blue by the ashes and their zeolitic products. The data obtained for adsorption of Cd 2+ on RHA, ZMA, and ZMB was found to best fit in the Langmuir isotherm model while WHA and WHAR data best fitted in the Freundlich model. Adsorption capacities for cadmium on RHA, WHA, WHAR, ZMA and ZMB adsorbents ions were 3.745, 52.00, 56.89, 11.24 and 22.22 mg/g respectively. The findings showed that incorporating the WHAR during synthesis of the zeolitic material enhanced its adsorption capacity and efficiency for Cd (II) ions and methylene blue.