Kevin P. Gable

Rhodium (I)-catalyzed cyclizations of 3-C-alkenyl pentodialdose derivatives

Abstract Cyclization of 1,2-isopropylidene 3-C-allyl ribo -pentodialdose, and 1-methylallyl and 3-C-vinyl analogs, with [(Ph3P)2RhCl]2 under CH2CH2 leads to intramolecular hydroacylation of the alkene with selective formation of cyclohexanones or cyclopentanones.

Rhenium and Technetium Oxo Complexes in the Study of Organic Oxidation Mechanisms

Publisher Summary This chapter outlines the mechanistic understanding of organic oxidation chemistry that has been generated by using high-valent metal oxo compounds of technetium and rhenium. Oxidation of organic compounds and alkenes, in particular, is an enormous area, and transition-metal-based catalysts have played a pivotal role. The similarity of the chemistries of rhenium and technetium elements with those of Mo, W, Ru, and Os makes them attractive models for probing reaction mechanisms for compounds of metals in the middle of the transition series. The chapter describes the preparation, structure, and chemical behavior of methyl rhenium trioxide (MTO) and discusses the bishydroxylation of alkenes. Detailed mechanistic inquiries into the mechanisms of transformations has shed light on several long-standing problems in organic oxidation chemistry and has revealed the importance of important structural classes of metal oxo and peroxo complexes.

p-Aminophenyl 1-thio-β-d-cellobioside: Synthesis and application in affinity chromatography of exo-type cellulases

Abstract p- Aminophenyl 1-thio-β- d -cellobioside (APTC) is shown to be a functional affinity ligand for the separation of exo-(cellobiohydrolases) and endo-(endoglucanases) acting cellulases. APTC is prepared by direct attachment of p-aminobenzenethiol to 2,3,6- tri -O- acetyl -4-O-(2,3,4,6- tetra -O- acetyl-β- d -glucopyranosyl)-(β- d -glucopyranosyl bromide, and subsequent deacetylation. APTC has been coupled to N-hydroxysuccinimide- activated agarose for affinity chromatography. Trichoderma reesei cellulases were used as representative enzymes. The behavior of these enzymes on APTC-affinity columns was essentially equivalent to that reported for the same enzymes on p- aminobenzyl 1-thio-β- d -cellobioside (ABTC)-columns; ABTC being the traditional ligand for affinity chromatography of exocellulase. The major cellobiohydrolases are retained on these columns, whereas the major endoglucanases are not. The cellobiohydrolases may be eluted from the columns by the addition of cellobiose to the mobile phase. The primary advantage of the APTC-ligand over other affinity ligands is its ease of preparation; the preparation of APTC requires approximately one-half the number of synthetic steps as required for the preparation of ABTC.

Reaction of O-allyl glucose with [(Ph3P)2RhCl]2: an intramolecular H2 transfer

Abstract Reaction of 3-O-allyl glucose with [(Ph 3 P) 2 RhCl] 2 at temperatures below 60°C leads to isomerization of the double bond to form a vinyl ether. Reaction at temperatures above 100°C in N-methylpyrrolidone leads to formation of propyl and propenyl glucono-[1,4]-lactone derivatives, identified as their triacetates, as well as to a decarbonylated product.

Spectroscopic Study of the Uranyl–Acetohydroxamate Adduct with Tributyl Phosphate

The ultraviolet–visible (UV-Vis) and Fourier transform infrared (FT-IR) spectroscopic studies carried out for the system UO2(NO3)/AHA/TBP (uranyl–acetohydroxamate–tributyl phosphate) confirmed the presence of the adduct of UO2(NO3)(AHA) ·2TBP with 1:1 stoichiometry for UO2:AHA (acetohydroxamic acid). The spectrum of this complex is identical to the infrared spectrum of the organic phase formed in the uranium distribution experiments with 30% TBP/n-dodecane and AHA present in aqueous phase. Disappearance of the hydroxyl stretching band and a shift in the position of the carbonyl band in the infrared spectra revealed that both the hydroxyl and the carbonyl group of acetohydroxamic acid are involved in the chelate ring with uranium. Also, acetic acid, accrued after acidic hydrolysis of acetohydroxamic acid, was identified in the extraction organic phase.

Use of ozone as an oxygen atom transfer agent in the synthesis of pentamethylcyclopentadienyl rhenium trioxide

Abstract Reaction of ozone with (η-C5(CH3)5)Re(CO)3 leads to oxidative decarbonylation and a moderate to good yield of (η-C5(CH3)5)ReO3.

Catalytic deoxygenation of epoxides with (Cp*ReO)2(µ-O)2 and catalyst deactivation

In situ reduction of Cp*ReO3 by PPh3 to form (Cp*ReO)2(µ-O)2 allows catalytic deoxygenation of epoxides, however, conproportionation between the ReV and ReVII species to form clusters of {(Cp*Re)3(µ-O)6}2+(ReO4–)2 and new compound {(Cp*Re)3(µ2-O)3(µ3-O)3ReO3}+(ReO4–) leads to removal of rhenium from the catalytic cycle and loss of activity.